# Licensed under a 3-clause BSD style license - see LICENSE.rst

from astropy.table.table_helpers import ArrayWrapper
from astropy.coordinates.earth import EarthLocation
from astropy.units.quantity import Quantity
from collections import OrderedDict
from contextlib import nullcontext

import pytest
import numpy as np

from astropy.table import Table, QTable, TableMergeError, Column, MaskedColumn, NdarrayMixin
from astropy.table.operations import _get_out_class, join_skycoord, join_distance
from astropy import units as u
from astropy.utils import metadata
from astropy.utils.metadata import MergeConflictError
from astropy import table
from astropy.time import Time, TimeDelta
from astropy.coordinates import (SkyCoord, SphericalRepresentation,
                                 UnitSphericalRepresentation,
                                 CartesianRepresentation,
                                 BaseRepresentationOrDifferential,
                                 search_around_3d)
from astropy.coordinates.tests.test_representation import representation_equal
from astropy.coordinates.tests.helper import skycoord_equal
from astropy.utils.compat.optional_deps import HAS_SCIPY  # noqa


def sort_eq(list1, list2):
    return sorted(list1) == sorted(list2)


def check_mask(col, exp_mask):
    """Check that col.mask == exp_mask"""
    if hasattr(col, 'mask'):
        # Coerce expected mask into dtype of col.mask. In particular this is
        # needed for types like EarthLocation where the mask is a structured
        # array.
        exp_mask = np.array(exp_mask).astype(col.mask.dtype)
        out = np.all(col.mask == exp_mask)
    else:
        # With no mask the check is OK if all the expected mask values
        # are False (i.e. no auto-conversion to MaskedQuantity if it was
        # not required by the join).
        out = np.all(exp_mask == False)
    return out


class TestJoin():

    def _setup(self, t_cls=Table):
        lines1 = [' a   b   c ',
                  '  0 foo  L1',
                  '  1 foo  L2',
                  '  1 bar  L3',
                  '  2 bar  L4']
        lines2 = [' a   b   d ',
                  '  1 foo  R1',
                  '  1 foo  R2',
                  '  2 bar  R3',
                  '  4 bar  R4']
        self.t1 = t_cls.read(lines1, format='ascii')
        self.t2 = t_cls.read(lines2, format='ascii')
        self.t3 = t_cls(self.t2, copy=True)

        self.t1.meta.update(OrderedDict([('b', [1, 2]), ('c', {'a': 1}), ('d', 1)]))
        self.t2.meta.update(OrderedDict([('b', [3, 4]), ('c', {'b': 1}), ('a', 1)]))
        self.t3.meta.update(OrderedDict([('b', 3), ('c', [1, 2]), ('d', 2), ('a', 1)]))

        self.meta_merge = OrderedDict([('b', [1, 2, 3, 4]),
                                       ('c', {'a': 1, 'b': 1}),
                                       ('d', 1),
                                       ('a', 1)])

    def test_table_meta_merge(self, operation_table_type):
        self._setup(operation_table_type)
        out = table.join(self.t1, self.t2, join_type='inner')
        assert out.meta == self.meta_merge

    def test_table_meta_merge_conflict(self, operation_table_type):
        self._setup(operation_table_type)

        with pytest.warns(metadata.MergeConflictWarning) as w:
            out = table.join(self.t1, self.t3, join_type='inner')
        assert len(w) == 3

        assert out.meta == self.t3.meta

        with pytest.warns(metadata.MergeConflictWarning) as w:
            out = table.join(self.t1, self.t3, join_type='inner', metadata_conflicts='warn')
        assert len(w) == 3

        assert out.meta == self.t3.meta

        out = table.join(self.t1, self.t3, join_type='inner', metadata_conflicts='silent')

        assert out.meta == self.t3.meta

        with pytest.raises(MergeConflictError):
            out = table.join(self.t1, self.t3, join_type='inner', metadata_conflicts='error')

        with pytest.raises(ValueError):
            out = table.join(self.t1, self.t3, join_type='inner', metadata_conflicts='nonsense')

    def test_both_unmasked_inner(self, operation_table_type):
        self._setup(operation_table_type)
        t1 = self.t1
        t2 = self.t2

        # Basic join with default parameters (inner join on common keys)
        t12 = table.join(t1, t2)
        assert type(t12) is operation_table_type
        assert type(t12['a']) is type(t1['a'])  # noqa
        assert type(t12['b']) is type(t1['b'])  # noqa
        assert type(t12['c']) is type(t1['c'])  # noqa
        assert type(t12['d']) is type(t2['d'])  # noqa
        assert t12.masked is False
        assert sort_eq(t12.pformat(), [' a   b   c   d ',
                                       '--- --- --- ---',
                                       '  1 foo  L2  R1',
                                       '  1 foo  L2  R2',
                                       '  2 bar  L4  R3'])
        # Table meta merged properly
        assert t12.meta == self.meta_merge

    def test_both_unmasked_left_right_outer(self, operation_table_type):
        if operation_table_type is QTable:
            pytest.xfail('Quantity columns do not support masking.')
        self._setup(operation_table_type)
        t1 = self.t1
        t2 = self.t2

        # Left join
        t12 = table.join(t1, t2, join_type='left')
        assert t12.has_masked_columns is True
        assert t12.masked is False
        for name in ('a', 'b', 'c'):
            assert type(t12[name]) is Column
        assert type(t12['d']) is MaskedColumn
        assert sort_eq(t12.pformat(), [' a   b   c   d ',
                                       '--- --- --- ---',
                                       '  0 foo  L1  --',
                                       '  1 bar  L3  --',
                                       '  1 foo  L2  R1',
                                       '  1 foo  L2  R2',
                                       '  2 bar  L4  R3'])

        # Right join
        t12 = table.join(t1, t2, join_type='right')
        assert t12.has_masked_columns is True
        assert t12.masked is False
        assert sort_eq(t12.pformat(), [' a   b   c   d ',
                                       '--- --- --- ---',
                                       '  1 foo  L2  R1',
                                       '  1 foo  L2  R2',
                                       '  2 bar  L4  R3',
                                       '  4 bar  --  R4'])

        # Outer join
        t12 = table.join(t1, t2, join_type='outer')
        assert t12.has_masked_columns is True
        assert t12.masked is False
        assert sort_eq(t12.pformat(), [' a   b   c   d ',
                                       '--- --- --- ---',
                                       '  0 foo  L1  --',
                                       '  1 bar  L3  --',
                                       '  1 foo  L2  R1',
                                       '  1 foo  L2  R2',
                                       '  2 bar  L4  R3',
                                       '  4 bar  --  R4'])

        # Check that the common keys are 'a', 'b'
        t12a = table.join(t1, t2, join_type='outer')
        t12b = table.join(t1, t2, join_type='outer', keys=['a', 'b'])
        assert np.all(t12a.as_array() == t12b.as_array())

    def test_both_unmasked_single_key_inner(self, operation_table_type):
        self._setup(operation_table_type)
        t1 = self.t1
        t2 = self.t2

        # Inner join on 'a' column
        t12 = table.join(t1, t2, keys='a')
        assert type(t12) is operation_table_type
        assert type(t12['a']) is type(t1['a'])  # noqa
        assert type(t12['b_1']) is type(t1['b'])  # noqa
        assert type(t12['c']) is type(t1['c'])  # noqa
        assert type(t12['b_2']) is type(t2['b'])  # noqa
        assert type(t12['d']) is type(t2['d'])  # noqa
        assert t12.masked is False
        assert sort_eq(t12.pformat(), [' a  b_1  c  b_2  d ',
                                       '--- --- --- --- ---',
                                       '  1 foo  L2 foo  R1',
                                       '  1 foo  L2 foo  R2',
                                       '  1 bar  L3 foo  R1',
                                       '  1 bar  L3 foo  R2',
                                       '  2 bar  L4 bar  R3'])

    def test_both_unmasked_single_key_left_right_outer(self, operation_table_type):
        if operation_table_type is QTable:
            pytest.xfail('Quantity columns do not support masking.')
        self._setup(operation_table_type)
        t1 = self.t1
        t2 = self.t2

        # Left join
        t12 = table.join(t1, t2, join_type='left', keys='a')
        assert t12.has_masked_columns is True
        assert sort_eq(t12.pformat(), [' a  b_1  c  b_2  d ',
                                       '--- --- --- --- ---',
                                       '  0 foo  L1  --  --',
                                       '  1 foo  L2 foo  R1',
                                       '  1 foo  L2 foo  R2',
                                       '  1 bar  L3 foo  R1',
                                       '  1 bar  L3 foo  R2',
                                       '  2 bar  L4 bar  R3'])

        # Right join
        t12 = table.join(t1, t2, join_type='right', keys='a')
        assert t12.has_masked_columns is True
        assert sort_eq(t12.pformat(), [' a  b_1  c  b_2  d ',
                                       '--- --- --- --- ---',
                                       '  1 foo  L2 foo  R1',
                                       '  1 foo  L2 foo  R2',
                                       '  1 bar  L3 foo  R1',
                                       '  1 bar  L3 foo  R2',
                                       '  2 bar  L4 bar  R3',
                                       '  4  --  -- bar  R4'])

        # Outer join
        t12 = table.join(t1, t2, join_type='outer', keys='a')
        assert t12.has_masked_columns is True
        assert sort_eq(t12.pformat(), [' a  b_1  c  b_2  d ',
                                       '--- --- --- --- ---',
                                       '  0 foo  L1  --  --',
                                       '  1 foo  L2 foo  R1',
                                       '  1 foo  L2 foo  R2',
                                       '  1 bar  L3 foo  R1',
                                       '  1 bar  L3 foo  R2',
                                       '  2 bar  L4 bar  R3',
                                       '  4  --  -- bar  R4'])

    def test_masked_unmasked(self, operation_table_type):
        if operation_table_type is QTable:
            pytest.xfail('Quantity columns do not support masking.')
        self._setup(operation_table_type)
        t1 = self.t1
        t1m = operation_table_type(self.t1, masked=True)
        t2 = self.t2

        # Result table is never masked
        t1m2 = table.join(t1m, t2, join_type='inner')
        assert t1m2.masked is False

        # Result should match non-masked result
        t12 = table.join(t1, t2)
        assert np.all(t12.as_array() == np.array(t1m2))

        # Mask out some values in left table and make sure they propagate
        t1m['b'].mask[1] = True
        t1m['c'].mask[2] = True
        t1m2 = table.join(t1m, t2, join_type='inner', keys='a')
        assert sort_eq(t1m2.pformat(), [' a  b_1  c  b_2  d ',
                                        '--- --- --- --- ---',
                                        '  1  --  L2 foo  R1',
                                        '  1  --  L2 foo  R2',
                                        '  1 bar  -- foo  R1',
                                        '  1 bar  -- foo  R2',
                                        '  2 bar  L4 bar  R3'])

        t21m = table.join(t2, t1m, join_type='inner', keys='a')
        assert sort_eq(t21m.pformat(), [' a  b_1  d  b_2  c ',
                                        '--- --- --- --- ---',
                                        '  1 foo  R2  --  L2',
                                        '  1 foo  R2 bar  --',
                                        '  1 foo  R1  --  L2',
                                        '  1 foo  R1 bar  --',
                                        '  2 bar  R3 bar  L4'])

    def test_masked_masked(self, operation_table_type):
        self._setup(operation_table_type)
        """Two masked tables"""
        if operation_table_type is QTable:
            pytest.xfail('Quantity columns do not support masking.')
        t1 = self.t1
        t1m = operation_table_type(self.t1, masked=True)
        t2 = self.t2
        t2m = operation_table_type(self.t2, masked=True)

        # Result table is never masked but original column types are preserved
        t1m2m = table.join(t1m, t2m, join_type='inner')
        assert t1m2m.masked is False
        for col in t1m2m.itercols():
            assert type(col) is MaskedColumn

        # Result should match non-masked result
        t12 = table.join(t1, t2)
        assert np.all(t12.as_array() == np.array(t1m2m))

        # Mask out some values in both tables and make sure they propagate
        t1m['b'].mask[1] = True
        t1m['c'].mask[2] = True
        t2m['d'].mask[2] = True
        t1m2m = table.join(t1m, t2m, join_type='inner', keys='a')
        assert sort_eq(t1m2m.pformat(), [' a  b_1  c  b_2  d ',
                                         '--- --- --- --- ---',
                                         '  1  --  L2 foo  R1',
                                         '  1  --  L2 foo  R2',
                                         '  1 bar  -- foo  R1',
                                         '  1 bar  -- foo  R2',
                                         '  2 bar  L4 bar  --'])

    def test_classes(self):
        """Ensure that classes and subclasses get through as expected"""
        class MyCol(Column):
            pass

        class MyMaskedCol(MaskedColumn):
            pass

        t1 = Table()
        t1['a'] = MyCol([1])
        t1['b'] = MyCol([2])
        t1['c'] = MyMaskedCol([3])

        t2 = Table()
        t2['a'] = Column([1, 2])
        t2['d'] = MyCol([3, 4])
        t2['e'] = MyMaskedCol([5, 6])

        t12 = table.join(t1, t2, join_type='inner')
        for name, exp_type in (('a', MyCol), ('b', MyCol), ('c', MyMaskedCol),
                               ('d', MyCol), ('e', MyMaskedCol)):
            assert type(t12[name] is exp_type)

        t21 = table.join(t2, t1, join_type='left')
        # Note col 'b' gets upgraded from MyCol to MaskedColumn since it needs to be
        # masked, but col 'c' stays since MyMaskedCol supports masking.
        for name, exp_type in (('a', MyCol), ('b', MaskedColumn), ('c', MyMaskedCol),
                               ('d', MyCol), ('e', MyMaskedCol)):
            assert type(t21[name] is exp_type)

    def test_col_rename(self, operation_table_type):
        self._setup(operation_table_type)
        """
        Test auto col renaming when there is a conflict.  Use
        non-default values of uniq_col_name and table_names.
        """
        t1 = self.t1
        t2 = self.t2
        t12 = table.join(t1, t2, uniq_col_name='x_{table_name}_{col_name}_y',
                         table_names=['L', 'R'], keys='a')
        assert t12.colnames == ['a', 'x_L_b_y', 'c', 'x_R_b_y', 'd']

    def test_rename_conflict(self, operation_table_type):
        self._setup(operation_table_type)
        """
        Test that auto-column rename fails because of a conflict
        with an existing column
        """
        t1 = self.t1
        t2 = self.t2
        t1['b_1'] = 1  # Add a new column b_1 that will conflict with auto-rename
        with pytest.raises(TableMergeError):
            table.join(t1, t2, keys='a')

    def test_missing_keys(self, operation_table_type):
        self._setup(operation_table_type)
        """Merge on a key column that doesn't exist"""
        t1 = self.t1
        t2 = self.t2
        with pytest.raises(TableMergeError):
            table.join(t1, t2, keys=['a', 'not there'])

    def test_bad_join_type(self, operation_table_type):
        self._setup(operation_table_type)
        """Bad join_type input"""
        t1 = self.t1
        t2 = self.t2
        with pytest.raises(ValueError):
            table.join(t1, t2, join_type='illegal value')

    def test_no_common_keys(self, operation_table_type):
        self._setup(operation_table_type)
        """Merge tables with no common keys"""
        t1 = self.t1
        t2 = self.t2
        del t1['a']
        del t1['b']
        del t2['a']
        del t2['b']
        with pytest.raises(TableMergeError):
            table.join(t1, t2)

    def test_masked_key_column(self, operation_table_type):
        self._setup(operation_table_type)
        """Merge on a key column that has a masked element"""
        if operation_table_type is QTable:
            pytest.xfail('Quantity columns do not support masking.')
        t1 = self.t1
        t2 = operation_table_type(self.t2, masked=True)
        table.join(t1, t2)  # OK
        t2['a'].mask[0] = True
        with pytest.raises(TableMergeError):
            table.join(t1, t2)

    def test_col_meta_merge(self, operation_table_type):
        self._setup(operation_table_type)
        t1 = self.t1
        t2 = self.t2
        t2.rename_column('d', 'c')  # force col conflict and renaming
        meta1 = OrderedDict([('b', [1, 2]), ('c', {'a': 1}), ('d', 1)])
        meta2 = OrderedDict([('b', [3, 4]), ('c', {'b': 1}), ('a', 1)])

        # Key col 'a', should first value ('cm')
        t1['a'].unit = 'cm'
        t2['a'].unit = 'm'
        # Key col 'b', take first value 't1_b'
        t1['b'].info.description = 't1_b'
        # Key col 'b', take first non-empty value 't1_b'
        t2['b'].info.format = '%6s'
        # Key col 'a', should be merged meta
        t1['a'].info.meta = meta1
        t2['a'].info.meta = meta2
        # Key col 'b', should be meta2
        t2['b'].info.meta = meta2

        # All these should pass through
        t1['c'].info.format = '%3s'
        t1['c'].info.description = 't1_c'

        t2['c'].info.format = '%6s'
        t2['c'].info.description = 't2_c'

        if operation_table_type is Table:
            ctx = pytest.warns(metadata.MergeConflictWarning, match=r"In merged column 'a' the 'unit' attribute does not match \(cm != m\)")  # noqa
        else:
            ctx = nullcontext()

        with ctx:
            t12 = table.join(t1, t2, keys=['a', 'b'])

        assert t12['a'].unit == 'm'
        assert t12['b'].info.description == 't1_b'
        assert t12['b'].info.format == '%6s'
        assert t12['a'].info.meta == self.meta_merge
        assert t12['b'].info.meta == meta2
        assert t12['c_1'].info.format == '%3s'
        assert t12['c_1'].info.description == 't1_c'
        assert t12['c_2'].info.format == '%6s'
        assert t12['c_2'].info.description == 't2_c'

    def test_join_multidimensional(self, operation_table_type):
        self._setup(operation_table_type)

        # Regression test for #2984, which was an issue where join did not work
        # on multi-dimensional columns.

        t1 = operation_table_type()
        t1['a'] = [1, 2, 3]
        t1['b'] = np.ones((3, 4))

        t2 = operation_table_type()
        t2['a'] = [1, 2, 3]
        t2['c'] = [4, 5, 6]

        t3 = table.join(t1, t2)

        np.testing.assert_allclose(t3['a'], t1['a'])
        np.testing.assert_allclose(t3['b'], t1['b'])
        np.testing.assert_allclose(t3['c'], t2['c'])

    def test_join_multidimensional_masked(self, operation_table_type):
        self._setup(operation_table_type)
        """
        Test for outer join with multidimensional columns where masking is required.
        (Issue #4059).
        """
        if operation_table_type is QTable:
            pytest.xfail('Quantity columns do not support masking.')

        a = table.MaskedColumn([1, 2, 3], name='a')
        a2 = table.Column([1, 3, 4], name='a')
        b = table.MaskedColumn([[1, 2],
                                [3, 4],
                                [5, 6]],
                               name='b',
                               mask=[[1, 0],
                                     [0, 1],
                                     [0, 0]])
        c = table.Column([[1, 1],
                          [2, 2],
                          [3, 3]],
                         name='c')
        t1 = operation_table_type([a, b])
        t2 = operation_table_type([a2, c])
        t12 = table.join(t1, t2, join_type='inner')

        assert np.all(t12['b'].mask == [[True, False],
                                        [False, False]])
        assert not hasattr(t12['c'], 'mask')

        t12 = table.join(t1, t2, join_type='outer')
        assert np.all(t12['b'].mask == [[True, False],
                                        [False, True],
                                        [False, False],
                                        [True, True]])
        assert np.all(t12['c'].mask == [[False, False],
                                        [True, True],
                                        [False, False],
                                        [False, False]])

    def test_mixin_functionality(self, mixin_cols):
        col = mixin_cols['m']
        cls_name = type(col).__name__
        len_col = len(col)
        idx = np.arange(len_col)
        t1 = table.QTable([idx, col], names=['idx', 'm1'])
        t2 = table.QTable([idx, col], names=['idx', 'm2'])
        # Set up join mismatches for different join_type cases
        t1 = t1[[0, 1, 3]]
        t2 = t2[[0, 2, 3]]

        # Test inner join, which works for all mixin_cols
        out = table.join(t1, t2, join_type='inner')
        assert len(out) == 2
        assert out['m2'].__class__ is col.__class__
        assert np.all(out['idx'] == [0, 3])
        if cls_name == 'SkyCoord':
            # SkyCoord doesn't support __eq__ so use our own
            assert skycoord_equal(out['m1'], col[[0, 3]])
            assert skycoord_equal(out['m2'], col[[0, 3]])
        elif 'Repr' in cls_name or 'Diff' in cls_name:
            assert np.all(representation_equal(out['m1'], col[[0, 3]]))
            assert np.all(representation_equal(out['m2'], col[[0, 3]]))
        else:
            assert np.all(out['m1'] == col[[0, 3]])
            assert np.all(out['m2'] == col[[0, 3]])

        # Check for left, right, outer join which requires masking. Works for
        # the listed mixins classes.
        if isinstance(col, (Quantity, Time, TimeDelta)):
            out = table.join(t1, t2, join_type='left')
            assert len(out) == 3
            assert np.all(out['idx'] == [0, 1, 3])
            assert np.all(out['m1'] == t1['m1'])
            assert np.all(out['m2'] == t2['m2'])
            check_mask(out['m1'], [False, False, False])
            check_mask(out['m2'], [False, True, False])

            out = table.join(t1, t2, join_type='right')
            assert len(out) == 3
            assert np.all(out['idx'] == [0, 2, 3])
            assert np.all(out['m1'] == t1['m1'])
            assert np.all(out['m2'] == t2['m2'])
            check_mask(out['m1'], [False, True, False])
            check_mask(out['m2'], [False, False, False])

            out = table.join(t1, t2, join_type='outer')
            assert len(out) == 4
            assert np.all(out['idx'] == [0, 1, 2, 3])
            assert np.all(out['m1'] == col)
            assert np.all(out['m2'] == col)
            assert check_mask(out['m1'], [False, False, True, False])
            assert check_mask(out['m2'], [False, True, False, False])
        else:
            # Otherwise make sure it fails with the right exception message
            for join_type in ('outer', 'left', 'right'):
                with pytest.raises(NotImplementedError) as err:
                    table.join(t1, t2, join_type=join_type)
                assert ('join requires masking' in str(err.value)
                        or 'join unavailable' in str(err.value))

    def test_cartesian_join(self, operation_table_type):
        t1 = Table(rows=[(1, 'a'),
                         (2, 'b')], names=['a', 'b'])
        t2 = Table(rows=[(3, 'c'),
                         (4, 'd')], names=['a', 'c'])
        t12 = table.join(t1, t2, join_type='cartesian')

        assert t1.colnames == ['a', 'b']
        assert t2.colnames == ['a', 'c']
        assert len(t12) == len(t1) * len(t2)
        assert str(t12).splitlines() == [
            'a_1  b  a_2  c ',
            '--- --- --- ---',
            '  1   a   3   c',
            '  1   a   4   d',
            '  2   b   3   c',
            '  2   b   4   d']

        with pytest.raises(ValueError, match='cannot supply keys for a cartesian join'):
            t12 = table.join(t1, t2, join_type='cartesian', keys='a')

    @pytest.mark.skipif('not HAS_SCIPY')
    def test_join_with_join_skycoord_sky(self):
        sc1 = SkyCoord([0, 1, 1.1, 2], [0, 0, 0, 0], unit='deg')
        sc2 = SkyCoord([0.5, 1.05, 2.1], [0, 0, 0], unit='deg')
        t1 = Table([sc1], names=['sc'])
        t2 = Table([sc2], names=['sc'])
        t12 = table.join(t1, t2, join_funcs={'sc': join_skycoord(0.2 * u.deg)})
        exp = ['sc_id   sc_1    sc_2  ',
               '      deg,deg deg,deg ',
               '----- ------- --------',
               '    1 1.0,0.0 1.05,0.0',
               '    1 1.1,0.0 1.05,0.0',
               '    2 2.0,0.0  2.1,0.0']
        assert str(t12).splitlines() == exp

    @pytest.mark.skipif('not HAS_SCIPY')
    @pytest.mark.parametrize('distance_func', ['search_around_3d', search_around_3d])
    def test_join_with_join_skycoord_3d(self, distance_func):
        sc1 = SkyCoord([0, 1, 1.1, 2]*u.deg, [0, 0, 0, 0]*u.deg, [1, 1, 2, 1]*u.m)
        sc2 = SkyCoord([0.5, 1.05, 2.1]*u.deg, [0, 0, 0]*u.deg, [1, 1, 1]*u.m)
        t1 = Table([sc1], names=['sc'])
        t2 = Table([sc2], names=['sc'])
        join_func = join_skycoord(np.deg2rad(0.2) * u.m,
                                  distance_func=distance_func)
        t12 = table.join(t1, t2, join_funcs={'sc': join_func})
        exp = ['sc_id     sc_1        sc_2    ',
               '       deg,deg,m   deg,deg,m  ',
               '----- ----------- ------------',
               '    1 1.0,0.0,1.0 1.05,0.0,1.0',
               '    2 2.0,0.0,1.0  2.1,0.0,1.0']
        assert str(t12).splitlines() == exp

    @pytest.mark.skipif('not HAS_SCIPY')
    def test_join_with_join_distance_1d(self):
        c1 = [0, 1, 1.1, 2]
        c2 = [0.5, 1.05, 2.1]
        t1 = Table([c1], names=['col'])
        t2 = Table([c2], names=['col'])
        join_func = join_distance(0.2,
                                  kdtree_args={'leafsize': 32},
                                  query_args={'p': 2})
        t12 = table.join(t1, t2, join_type='outer', join_funcs={'col': join_func})
        exp = ['col_id col_1 col_2',
               '------ ----- -----',
               '     1   1.0  1.05',
               '     1   1.1  1.05',
               '     2   2.0   2.1',
               '     3   0.0    --',
               '     4    --   0.5']
        assert str(t12).splitlines() == exp

    @pytest.mark.skipif('not HAS_SCIPY')
    def test_join_with_join_distance_1d_multikey(self):
        from astropy.table.operations import _apply_join_funcs

        c1 = [0, 1, 1.1, 1.2, 2]
        id1 = [0, 1, 2, 2, 3]
        o1 = ['a', 'b', 'c', 'd', 'e']
        c2 = [0.5, 1.05, 2.1]
        id2 = [0, 2, 4]
        o2 = ['z', 'y', 'x']
        t1 = Table([c1, id1, o1], names=['col', 'id', 'o1'])
        t2 = Table([c2, id2, o2], names=['col', 'id', 'o2'])
        join_func = join_distance(0.2)
        join_funcs = {'col': join_func}
        t12 = table.join(t1, t2, join_type='outer', join_funcs=join_funcs)
        exp = ['col_id col_1  id  o1 col_2  o2',
               '------ ----- --- --- ----- ---',
               '     1   1.0   1   b    --  --',
               '     1   1.1   2   c  1.05   y',
               '     1   1.2   2   d  1.05   y',
               '     2   2.0   3   e    --  --',
               '     2    --   4  --   2.1   x',
               '     3   0.0   0   a    --  --',
               '     4    --   0  --   0.5   z']
        assert str(t12).splitlines() == exp

        left, right, keys = _apply_join_funcs(t1, t2, ('col', 'id'), join_funcs)
        assert keys == ('col_id', 'id')

    @pytest.mark.skipif('not HAS_SCIPY')
    def test_join_with_join_distance_1d_quantity(self):
        c1 = [0, 1, 1.1, 2] * u.m
        c2 = [500, 1050, 2100] * u.mm
        t1 = QTable([c1], names=['col'])
        t2 = QTable([c2], names=['col'])
        join_func = join_distance(20 * u.cm)
        t12 = table.join(t1, t2, join_funcs={'col': join_func})
        exp = ['col_id col_1 col_2 ',
               '         m     mm  ',
               '------ ----- ------',
               '     1   1.0 1050.0',
               '     1   1.1 1050.0',
               '     2   2.0 2100.0']
        assert str(t12).splitlines() == exp

        # Generate column name conflict
        t2['col_id'] = [0, 0, 0]
        t2['col__id'] = [0, 0, 0]
        t12 = table.join(t1, t2, join_funcs={'col': join_func})
        exp = ['col___id col_1 col_2  col_id col__id',
               '           m     mm                 ',
               '-------- ----- ------ ------ -------',
               '       1   1.0 1050.0      0       0',
               '       1   1.1 1050.0      0       0',
               '       2   2.0 2100.0      0       0']
        assert str(t12).splitlines() == exp

    @pytest.mark.skipif('not HAS_SCIPY')
    def test_join_with_join_distance_2d(self):
        c1 = np.array([[0, 1, 1.1, 2],
                       [0, 0, 1, 0]]).transpose()
        c2 = np.array([[0.5, 1.05, 2.1],
                       [0, 0, 0]]).transpose()
        t1 = Table([c1], names=['col'])
        t2 = Table([c2], names=['col'])
        join_func = join_distance(0.2,
                                  kdtree_args={'leafsize': 32},
                                  query_args={'p': 2})
        t12 = table.join(t1, t2, join_type='outer', join_funcs={'col': join_func})
        exp = ['col_id   col_1       col_2   ',
               f'{t12["col_id"].dtype.name}  float64[2]  float64[2]',  # int32 or int64
               '------ ---------- -----------',
               '     1 1.0 .. 0.0 1.05 .. 0.0',
               '     2 2.0 .. 0.0  2.1 .. 0.0',
               '     3 0.0 .. 0.0    -- .. --',
               '     4 1.1 .. 1.0    -- .. --',
               '     5   -- .. --  0.5 .. 0.0']
        assert t12.pformat(show_dtype=True) == exp

    def test_keys_left_right_basic(self):
        """Test using the keys_left and keys_right args to specify different
        join keys. This takes the standard test case but renames column 'a'
        to 'x' and 'y' respectively for tables 1 and 2. Then it compares the
        normal join on 'a' to the new join on 'x' and 'y'."""
        self._setup()

        for join_type in ('inner', 'left', 'right', 'outer'):
            t1 = self.t1.copy()
            t2 = self.t2.copy()
            # Expected is same as joining on 'a' but with names 'x', 'y' instead
            t12_exp = table.join(t1, t2, keys='a', join_type=join_type)
            t12_exp.add_column(t12_exp['a'], name='x', index=1)
            t12_exp.add_column(t12_exp['a'], name='y', index=len(t1.colnames) + 1)
            del t12_exp['a']

            # Different key names
            t1.rename_column('a', 'x')
            t2.rename_column('a', 'y')
            keys_left_list = ['x']  # Test string key name
            keys_right_list = [['y']]  # Test list of string key names
            if join_type == 'outer':
                # Just do this for the outer join (others are the same)
                keys_left_list.append([t1['x'].tolist()])  # Test list key column
                keys_right_list.append([t2['y']])  # Test Column key column

            for keys_left, keys_right in zip(keys_left_list, keys_right_list):
                t12 = table.join(t1, t2, keys_left=keys_left, keys_right=keys_right,
                                 join_type=join_type)

                assert t12.colnames == t12_exp.colnames
                for col in t12.values_equal(t12_exp).itercols():
                    assert np.all(col)
                assert t12_exp.meta == t12.meta

    def test_keys_left_right_exceptions(self):
        """Test exceptions using the keys_left and keys_right args to specify
        different join keys.
        """
        self._setup()
        t1 = self.t1
        t2 = self.t2

        msg = r"left table does not have key column 'z'"
        with pytest.raises(ValueError, match=msg):
            table.join(t1, t2, keys_left='z', keys_right=['a'])

        msg = r"left table has different length from key \[1, 2\]"
        with pytest.raises(ValueError, match=msg):
            table.join(t1, t2, keys_left=[[1, 2]], keys_right=['a'])

        msg = r"keys arg must be None if keys_left and keys_right are supplied"
        with pytest.raises(ValueError, match=msg):
            table.join(t1, t2, keys_left='z', keys_right=['a'], keys='a')

        msg = r"keys_left and keys_right args must have same length"
        with pytest.raises(ValueError, match=msg):
            table.join(t1, t2, keys_left=['a', 'b'], keys_right=['a'])

        msg = r"keys_left and keys_right must both be provided"
        with pytest.raises(ValueError, match=msg):
            table.join(t1, t2, keys_left=['a', 'b'])

        msg = r"cannot supply join_funcs arg and keys_left / keys_right"
        with pytest.raises(ValueError, match=msg):
            table.join(t1, t2, keys_left=['a'], keys_right=['a'], join_funcs={})


class TestSetdiff():

    def _setup(self, t_cls=Table):
        lines1 = [' a   b ',
                  '  0 foo ',
                  '  1 foo ',
                  '  1 bar ',
                  '  2 bar ']
        lines2 = [' a   b ',
                  '  0 foo ',
                  '  3 foo ',
                  '  4 bar ',
                  '  2 bar ']
        lines3 = [' a   b   d ',
                  '  0 foo  R1',
                  '  8 foo  R2',
                  '  1 bar  R3',
                  '  4 bar  R4']
        self.t1 = t_cls.read(lines1, format='ascii')
        self.t2 = t_cls.read(lines2, format='ascii')
        self.t3 = t_cls.read(lines3, format='ascii')

    def test_default_same_columns(self, operation_table_type):
        self._setup(operation_table_type)
        out = table.setdiff(self.t1, self.t2)
        assert type(out['a']) is type(self.t1['a'])  # noqa
        assert type(out['b']) is type(self.t1['b'])  # noqa
        assert out.pformat() == [' a   b ',
                                 '--- ---',
                                 '  1 bar',
                                 '  1 foo']

    def test_default_same_tables(self, operation_table_type):
        self._setup(operation_table_type)
        out = table.setdiff(self.t1, self.t1)

        assert type(out['a']) is type(self.t1['a'])  # noqa
        assert type(out['b']) is type(self.t1['b'])  # noqa
        assert out.pformat() == [' a   b ',
                                 '--- ---']

    def test_extra_col_left_table(self, operation_table_type):
        self._setup(operation_table_type)

        with pytest.raises(ValueError):
            table.setdiff(self.t3, self.t1)

    def test_extra_col_right_table(self, operation_table_type):
        self._setup(operation_table_type)
        out = table.setdiff(self.t1, self.t3)

        assert type(out['a']) is type(self.t1['a'])  # noqa
        assert type(out['b']) is type(self.t1['b'])  # noqa
        assert out.pformat() == [' a   b ',
                                 '--- ---',
                                 '  1 foo',
                                 '  2 bar']

    def test_keys(self, operation_table_type):
        self._setup(operation_table_type)
        out = table.setdiff(self.t3, self.t1, keys=['a', 'b'])

        assert type(out['a']) is type(self.t1['a'])  # noqa
        assert type(out['b']) is type(self.t1['b'])  # noqa
        assert out.pformat() == [' a   b   d ',
                                 '--- --- ---',
                                 '  4 bar  R4',
                                 '  8 foo  R2']

    def test_missing_key(self, operation_table_type):
        self._setup(operation_table_type)

        with pytest.raises(ValueError):
            table.setdiff(self.t3, self.t1, keys=['a', 'd'])


class TestVStack():

    def _setup(self, t_cls=Table):
        self.t1 = t_cls.read([' a   b',
                              ' 0. foo',
                              ' 1. bar'], format='ascii')

        self.t2 = t_cls.read([' a    b   c',
                              ' 2.  pez  4',
                              ' 3.  sez  5'], format='ascii')

        self.t3 = t_cls.read([' a    b',
                              ' 4.   7',
                              ' 5.   8',
                              ' 6.   9'], format='ascii')
        self.t4 = t_cls(self.t1, copy=True, masked=t_cls is Table)

        # The following table has meta-data that conflicts with t1
        self.t5 = t_cls(self.t1, copy=True)

        self.t1.meta.update(OrderedDict([('b', [1, 2]), ('c', {'a': 1}), ('d', 1)]))
        self.t2.meta.update(OrderedDict([('b', [3, 4]), ('c', {'b': 1}), ('a', 1)]))
        self.t4.meta.update(OrderedDict([('b', [5, 6]), ('c', {'c': 1}), ('e', 1)]))
        self.t5.meta.update(OrderedDict([('b', 3), ('c', 'k'), ('d', 1)]))
        self.meta_merge = OrderedDict([('b', [1, 2, 3, 4, 5, 6]),
                                       ('c', {'a': 1, 'b': 1, 'c': 1}),
                                       ('d', 1),
                                       ('a', 1),
                                       ('e', 1)])

    def test_validate_join_type(self):
        self._setup()
        with pytest.raises(TypeError, match='Did you accidentally call vstack'):
            table.vstack(self.t1, self.t2)

    def test_stack_rows(self, operation_table_type):
        self._setup(operation_table_type)
        t2 = self.t1.copy()
        t2.meta.clear()
        out = table.vstack([self.t1, t2[1]])
        assert type(out['a']) is type(self.t1['a'])  # noqa
        assert type(out['b']) is type(self.t1['b'])  # noqa
        assert out.pformat() == [' a   b ',
                                 '--- ---',
                                 '0.0 foo',
                                 '1.0 bar',
                                 '1.0 bar']

    def test_stack_table_column(self, operation_table_type):
        self._setup(operation_table_type)
        t2 = self.t1.copy()
        t2.meta.clear()
        out = table.vstack([self.t1, t2['a']])
        assert out.masked is False
        assert out.pformat() == [' a   b ',
                                 '--- ---',
                                 '0.0 foo',
                                 '1.0 bar',
                                 '0.0  --',
                                 '1.0  --']

    def test_table_meta_merge(self, operation_table_type):
        self._setup(operation_table_type)
        out = table.vstack([self.t1, self.t2, self.t4], join_type='inner')
        assert out.meta == self.meta_merge

    def test_table_meta_merge_conflict(self, operation_table_type):
        self._setup(operation_table_type)

        with pytest.warns(metadata.MergeConflictWarning) as w:
            out = table.vstack([self.t1, self.t5], join_type='inner')
        assert len(w) == 2

        assert out.meta == self.t5.meta

        with pytest.warns(metadata.MergeConflictWarning) as w:
            out = table.vstack([self.t1, self.t5], join_type='inner', metadata_conflicts='warn')
        assert len(w) == 2

        assert out.meta == self.t5.meta

        out = table.vstack([self.t1, self.t5], join_type='inner', metadata_conflicts='silent')

        assert out.meta == self.t5.meta

        with pytest.raises(MergeConflictError):
            out = table.vstack([self.t1, self.t5], join_type='inner', metadata_conflicts='error')

        with pytest.raises(ValueError):
            out = table.vstack([self.t1, self.t5], join_type='inner', metadata_conflicts='nonsense')

    def test_bad_input_type(self, operation_table_type):
        self._setup(operation_table_type)
        with pytest.raises(ValueError):
            table.vstack([])
        with pytest.raises(TypeError):
            table.vstack(1)
        with pytest.raises(TypeError):
            table.vstack([self.t2, 1])
        with pytest.raises(ValueError):
            table.vstack([self.t1, self.t2], join_type='invalid join type')

    def test_stack_basic_inner(self, operation_table_type):
        self._setup(operation_table_type)
        t1 = self.t1
        t2 = self.t2
        t4 = self.t4

        t12 = table.vstack([t1, t2], join_type='inner')
        assert t12.masked is False
        assert type(t12) is operation_table_type
        assert type(t12['a']) is type(t1['a'])  # noqa
        assert type(t12['b']) is type(t1['b'])  # noqa
        assert t12.pformat() == [' a   b ',
                                 '--- ---',
                                 '0.0 foo',
                                 '1.0 bar',
                                 '2.0 pez',
                                 '3.0 sez']

        t124 = table.vstack([t1, t2, t4], join_type='inner')
        assert type(t124) is operation_table_type
        assert type(t12['a']) is type(t1['a'])  # noqa
        assert type(t12['b']) is type(t1['b'])  # noqa
        assert t124.pformat() == [' a   b ',
                                  '--- ---',
                                  '0.0 foo',
                                  '1.0 bar',
                                  '2.0 pez',
                                  '3.0 sez',
                                  '0.0 foo',
                                  '1.0 bar']

    def test_stack_basic_outer(self, operation_table_type):
        if operation_table_type is QTable:
            pytest.xfail('Quantity columns do not support masking.')
        self._setup(operation_table_type)
        t1 = self.t1
        t2 = self.t2
        t4 = self.t4
        t12 = table.vstack([t1, t2], join_type='outer')
        assert t12.masked is False
        assert t12.pformat() == [' a   b   c ',
                                 '--- --- ---',
                                 '0.0 foo  --',
                                 '1.0 bar  --',
                                 '2.0 pez   4',
                                 '3.0 sez   5']

        t124 = table.vstack([t1, t2, t4], join_type='outer')
        assert t124.masked is False
        assert t124.pformat() == [' a   b   c ',
                                  '--- --- ---',
                                  '0.0 foo  --',
                                  '1.0 bar  --',
                                  '2.0 pez   4',
                                  '3.0 sez   5',
                                  '0.0 foo  --',
                                  '1.0 bar  --']

    def test_stack_incompatible(self, operation_table_type):
        self._setup(operation_table_type)
        with pytest.raises(TableMergeError) as excinfo:
            table.vstack([self.t1, self.t3], join_type='inner')
        assert ("The 'b' columns have incompatible types: {}"
                .format([self.t1['b'].dtype.name, self.t3['b'].dtype.name])
                in str(excinfo.value))

        with pytest.raises(TableMergeError) as excinfo:
            table.vstack([self.t1, self.t3], join_type='outer')
        assert "The 'b' columns have incompatible types:" in str(excinfo.value)

        with pytest.raises(TableMergeError):
            table.vstack([self.t1, self.t2], join_type='exact')

        t1_reshape = self.t1.copy()
        t1_reshape['b'].shape = [2, 1]
        with pytest.raises(TableMergeError) as excinfo:
            table.vstack([self.t1, t1_reshape])
        assert "have different shape" in str(excinfo.value)

    def test_vstack_one_masked(self, operation_table_type):
        if operation_table_type is QTable:
            pytest.xfail('Quantity columns do not support masking.')
        self._setup(operation_table_type)
        t1 = self.t1
        t4 = self.t4
        t4['b'].mask[1] = True
        t14 = table.vstack([t1, t4])
        assert t14.masked is False
        assert t14.pformat() == [' a   b ',
                                 '--- ---',
                                 '0.0 foo',
                                 '1.0 bar',
                                 '0.0 foo',
                                 '1.0  --']

    def test_col_meta_merge_inner(self, operation_table_type):
        self._setup(operation_table_type)
        t1 = self.t1
        t2 = self.t2
        t4 = self.t4

        # Key col 'a', should last value ('km')
        t1['a'].info.unit = 'cm'
        t2['a'].info.unit = 'm'
        t4['a'].info.unit = 'km'

        # Key col 'a' format should take last when all match
        t1['a'].info.format = '%f'
        t2['a'].info.format = '%f'
        t4['a'].info.format = '%f'

        # Key col 'b', take first value 't1_b'
        t1['b'].info.description = 't1_b'

        # Key col 'b', take first non-empty value '%6s'
        t4['b'].info.format = '%6s'

        # Key col 'a', should be merged meta
        t1['a'].info.meta.update(OrderedDict([('b', [1, 2]), ('c', {'a': 1}), ('d', 1)]))
        t2['a'].info.meta.update(OrderedDict([('b', [3, 4]), ('c', {'b': 1}), ('a', 1)]))
        t4['a'].info.meta.update(OrderedDict([('b', [5, 6]), ('c', {'c': 1}), ('e', 1)]))

        # Key col 'b', should be meta2
        t2['b'].info.meta.update(OrderedDict([('b', [3, 4]), ('c', {'b': 1}), ('a', 1)]))

        if operation_table_type is Table:
            ctx = pytest.warns(metadata.MergeConflictWarning)
        else:
            ctx = nullcontext()

        with ctx as warning_lines:
            out = table.vstack([t1, t2, t4], join_type='inner')

        if operation_table_type is Table:
            assert len(warning_lines) == 2
            assert ("In merged column 'a' the 'unit' attribute does not match (cm != m)"
                    in str(warning_lines[0].message))
            assert ("In merged column 'a' the 'unit' attribute does not match (m != km)"
                    in str(warning_lines[1].message))
            # Check units are suitably ignored for a regular Table
            assert out.pformat() == ['   a       b   ',
                                     '   km          ',
                                     '-------- ------',
                                     '0.000000    foo',
                                     '1.000000    bar',
                                     '2.000000    pez',
                                     '3.000000    sez',
                                     '0.000000    foo',
                                     '1.000000    bar']
        else:
            # Check QTable correctly dealt with units.
            assert out.pformat() == ['   a       b   ',
                                     '   km          ',
                                     '-------- ------',
                                     '0.000000    foo',
                                     '0.000010    bar',
                                     '0.002000    pez',
                                     '0.003000    sez',
                                     '0.000000    foo',
                                     '1.000000    bar']
        assert out['a'].info.unit == 'km'
        assert out['a'].info.format == '%f'
        assert out['b'].info.description == 't1_b'
        assert out['b'].info.format == '%6s'
        assert out['a'].info.meta == self.meta_merge
        assert out['b'].info.meta == OrderedDict([('b', [3, 4]), ('c', {'b': 1}), ('a', 1)])

    def test_col_meta_merge_outer(self, operation_table_type):
        if operation_table_type is QTable:
            pytest.xfail('Quantity columns do not support masking.')
        self._setup(operation_table_type)
        t1 = self.t1
        t2 = self.t2
        t4 = self.t4

        # Key col 'a', should last value ('km')
        t1['a'].unit = 'cm'
        t2['a'].unit = 'm'
        t4['a'].unit = 'km'

        # Key col 'a' format should take last when all match
        t1['a'].info.format = '%0d'
        t2['a'].info.format = '%0d'
        t4['a'].info.format = '%0d'

        # Key col 'b', take first value 't1_b'
        t1['b'].info.description = 't1_b'

        # Key col 'b', take first non-empty value '%6s'
        t4['b'].info.format = '%6s'

        # Key col 'a', should be merged meta
        t1['a'].info.meta.update(OrderedDict([('b', [1, 2]), ('c', {'a': 1}), ('d', 1)]))
        t2['a'].info.meta.update(OrderedDict([('b', [3, 4]), ('c', {'b': 1}), ('a', 1)]))
        t4['a'].info.meta.update(OrderedDict([('b', [5, 6]), ('c', {'c': 1}), ('e', 1)]))

        # Key col 'b', should be meta2
        t2['b'].info.meta.update(OrderedDict([('b', [3, 4]), ('c', {'b': 1}), ('a', 1)]))

        # All these should pass through
        t2['c'].unit = 'm'
        t2['c'].info.format = '%6s'
        t2['c'].info.description = 't2_c'

        with pytest.warns(metadata.MergeConflictWarning) as warning_lines:
            out = table.vstack([t1, t2, t4], join_type='outer')

        assert len(warning_lines) == 2
        assert ("In merged column 'a' the 'unit' attribute does not match (cm != m)"
                in str(warning_lines[0].message))
        assert ("In merged column 'a' the 'unit' attribute does not match (m != km)"
                in str(warning_lines[1].message))
        assert out['a'].unit == 'km'
        assert out['a'].info.format == '%0d'
        assert out['b'].info.description == 't1_b'
        assert out['b'].info.format == '%6s'
        assert out['a'].info.meta == self.meta_merge
        assert out['b'].info.meta == OrderedDict([('b', [3, 4]), ('c', {'b': 1}), ('a', 1)])
        assert out['c'].info.unit == 'm'
        assert out['c'].info.format == '%6s'
        assert out['c'].info.description == 't2_c'

    def test_vstack_one_table(self, operation_table_type):
        self._setup(operation_table_type)
        """Regression test for issue #3313"""
        assert (self.t1 == table.vstack(self.t1)).all()
        assert (self.t1 == table.vstack([self.t1])).all()

    def test_mixin_functionality(self, mixin_cols):
        col = mixin_cols['m']
        len_col = len(col)
        t = table.QTable([col], names=['a'])
        cls_name = type(col).__name__

        # Vstack works for these classes:
        if isinstance(col, (u.Quantity, Time, TimeDelta, SkyCoord, EarthLocation,
                            BaseRepresentationOrDifferential)):
            out = table.vstack([t, t])
            assert len(out) == len_col * 2
            if cls_name == 'SkyCoord':
                # Argh, SkyCoord needs __eq__!!
                assert skycoord_equal(out['a'][len_col:], col)
                assert skycoord_equal(out['a'][:len_col], col)
            elif 'Repr' in cls_name or 'Diff' in cls_name:
                assert np.all(representation_equal(out['a'][:len_col], col))
                assert np.all(representation_equal(out['a'][len_col:], col))
            else:
                assert np.all(out['a'][:len_col] == col)
                assert np.all(out['a'][len_col:] == col)
        else:
            with pytest.raises(NotImplementedError) as err:
                table.vstack([t, t])
            assert ('vstack unavailable for mixin column type(s): {}'
                    .format(cls_name) in str(err.value))

        # Check for outer stack which requires masking.  Only Time supports
        # this currently.
        t2 = table.QTable([col], names=['b'])  # different from col name for t
        if isinstance(col, (Time, TimeDelta, Quantity)):
            out = table.vstack([t, t2], join_type='outer')
            assert len(out) == len_col * 2
            assert np.all(out['a'][:len_col] == col)
            assert np.all(out['b'][len_col:] == col)
            assert check_mask(out['a'], [False] * len_col + [True] * len_col)
            assert check_mask(out['b'], [True] * len_col + [False] * len_col)
            # check directly stacking mixin columns:
            out2 = table.vstack([t, t2['b']])
            assert np.all(out['a'] == out2['a'])
            assert np.all(out['b'] == out2['b'])
        else:
            with pytest.raises(NotImplementedError) as err:
                table.vstack([t, t2], join_type='outer')
            assert ('vstack requires masking' in str(err.value)
                    or 'vstack unavailable' in str(err.value))

    def test_vstack_different_representation(self):
        """Test that representations can be mixed together."""
        rep1 = CartesianRepresentation([1, 2]*u.km, [3, 4]*u.km, 1*u.km)
        rep2 = SphericalRepresentation([0]*u.deg, [0]*u.deg, 10*u.km)
        t1 = Table([rep1])
        t2 = Table([rep2])
        t12 = table.vstack([t1, t2])
        expected = CartesianRepresentation([1, 2, 10]*u.km,
                                           [3, 4, 0]*u.km,
                                           [1, 1, 0]*u.km)
        assert np.all(representation_equal(t12['col0'], expected))

        rep3 = UnitSphericalRepresentation([0]*u.deg, [0]*u.deg)
        t3 = Table([rep3])
        with pytest.raises(ValueError, match='representations are inconsistent'):
            table.vstack([t1, t3])


class TestDStack():

    def _setup(self, t_cls=Table):
        self.t1 = t_cls.read([' a   b',
                              ' 0. foo',
                              ' 1. bar'], format='ascii')

        self.t2 = t_cls.read([' a    b   c',
                              ' 2.  pez  4',
                              ' 3.  sez  5'], format='ascii')
        self.t2['d'] = Time([1, 2], format='cxcsec')

        self.t3 = t_cls({'a': [[5., 6.], [4., 3.]],
                         'b': [['foo', 'bar'], ['pez', 'sez']]},
                        names=('a', 'b'))

        self.t4 = t_cls(self.t1, copy=True, masked=t_cls is Table)

        self.t5 = t_cls({'a': [[4., 2.], [1., 6.]],
                         'b': [['foo', 'pez'], ['bar', 'sez']]},
                        names=('a', 'b'))
        self.t6 = t_cls.read([' a    b   c',
                              ' 7.  pez  2',
                              ' 4.  sez  6',
                              ' 6.  foo  3'], format='ascii')

    def test_validate_join_type(self):
        self._setup()
        with pytest.raises(TypeError, match='Did you accidentally call dstack'):
            table.dstack(self.t1, self.t2)

    @staticmethod
    def compare_dstack(tables, out):
        for ii, tbl in enumerate(tables):
            for name, out_col in out.columns.items():
                if name in tbl.colnames:
                    # Columns always compare equal
                    assert np.all(tbl[name] == out[name][:, ii])

                    # If input has a mask then output must have same mask
                    if hasattr(tbl[name], 'mask'):
                        assert np.all(tbl[name].mask == out[name].mask[:, ii])

                    # If input has no mask then output might have a mask (if other table
                    # is missing that column). If so then all mask values should be False.
                    elif hasattr(out[name], 'mask'):
                        assert not np.any(out[name].mask[:, ii])

                else:
                    # Column missing for this table, out must have a mask with all True.
                    assert np.all(out[name].mask[:, ii])

    def test_dstack_table_column(self, operation_table_type):
        """Stack a table with 3 cols and one column (gets auto-converted to Table).
        """
        self._setup(operation_table_type)
        t2 = self.t1.copy()
        out = table.dstack([self.t1, t2['a']])
        self.compare_dstack([self.t1, t2[('a',)]], out)

    def test_dstack_basic_outer(self, operation_table_type):
        if operation_table_type is QTable:
            pytest.xfail('Quantity columns do not support masking.')
        self._setup(operation_table_type)
        t1 = self.t1
        t2 = self.t2
        t4 = self.t4
        t4['a'].mask[0] = True
        # Test for non-masked table
        t12 = table.dstack([t1, t2], join_type='outer')
        assert type(t12) is operation_table_type
        assert type(t12['a']) is type(t1['a'])  # noqa
        assert type(t12['b']) is type(t1['b'])  # noqa
        self.compare_dstack([t1, t2], t12)

        # Test for masked table
        t124 = table.dstack([t1, t2, t4], join_type='outer')
        assert type(t124) is operation_table_type
        assert type(t124['a']) is type(t4['a'])  # noqa
        assert type(t124['b']) is type(t4['b'])  # noqa
        self.compare_dstack([t1, t2, t4], t124)

    def test_dstack_basic_inner(self, operation_table_type):
        self._setup(operation_table_type)
        t1 = self.t1
        t2 = self.t2
        t4 = self.t4

        # Test for masked table
        t124 = table.dstack([t1, t2, t4], join_type='inner')
        assert type(t124) is operation_table_type
        assert type(t124['a']) is type(t4['a'])  # noqa
        assert type(t124['b']) is type(t4['b'])  # noqa
        self.compare_dstack([t1, t2, t4], t124)

    def test_dstack_multi_dimension_column(self, operation_table_type):
        self._setup(operation_table_type)
        t3 = self.t3
        t5 = self.t5
        t2 = self.t2
        t35 = table.dstack([t3, t5])
        assert type(t35) is operation_table_type
        assert type(t35['a']) is type(t3['a'])  # noqa
        assert type(t35['b']) is type(t3['b'])  # noqa
        self.compare_dstack([t3, t5], t35)

        with pytest.raises(TableMergeError):
            table.dstack([t2, t3])

    def test_dstack_different_length_table(self, operation_table_type):
        self._setup(operation_table_type)
        t2 = self.t2
        t6 = self.t6
        with pytest.raises(ValueError):
            table.dstack([t2, t6])

    def test_dstack_single_table(self):
        self._setup(Table)
        out = table.dstack(self.t1)
        assert np.all(out == self.t1)

    def test_dstack_representation(self):
        rep1 = SphericalRepresentation([1, 2]*u.deg, [3, 4]*u.deg, 1*u.kpc)
        rep2 = SphericalRepresentation([10, 20]*u.deg, [30, 40]*u.deg, 10*u.kpc)
        t1 = Table([rep1])
        t2 = Table([rep2])
        t12 = table.dstack([t1, t2])
        assert np.all(representation_equal(t12['col0'][:, 0], rep1))
        assert np.all(representation_equal(t12['col0'][:, 1], rep2))

    def test_dstack_skycoord(self):
        sc1 = SkyCoord([1, 2]*u.deg, [3, 4]*u.deg)
        sc2 = SkyCoord([10, 20]*u.deg, [30, 40]*u.deg)
        t1 = Table([sc1])
        t2 = Table([sc2])
        t12 = table.dstack([t1, t2])
        assert skycoord_equal(sc1, t12['col0'][:, 0])
        assert skycoord_equal(sc2, t12['col0'][:, 1])


class TestHStack():

    def _setup(self, t_cls=Table):
        self.t1 = t_cls.read([' a    b',
                              ' 0. foo',
                              ' 1. bar'], format='ascii')

        self.t2 = t_cls.read([' a    b   c',
                              ' 2.  pez  4',
                              ' 3.  sez  5'], format='ascii')

        self.t3 = t_cls.read([' d    e',
                              ' 4.   7',
                              ' 5.   8',
                              ' 6.   9'], format='ascii')
        self.t4 = t_cls(self.t1, copy=True, masked=True)
        self.t4['a'].name = 'f'
        self.t4['b'].name = 'g'

        # The following table has meta-data that conflicts with t1
        self.t5 = t_cls(self.t1, copy=True)

        self.t1.meta.update(OrderedDict([('b', [1, 2]), ('c', {'a': 1}), ('d', 1)]))
        self.t2.meta.update(OrderedDict([('b', [3, 4]), ('c', {'b': 1}), ('a', 1)]))
        self.t4.meta.update(OrderedDict([('b', [5, 6]), ('c', {'c': 1}), ('e', 1)]))
        self.t5.meta.update(OrderedDict([('b', 3), ('c', 'k'), ('d', 1)]))
        self.meta_merge = OrderedDict([('b', [1, 2, 3, 4, 5, 6]),
                                       ('c', {'a': 1, 'b': 1, 'c': 1}),
                                       ('d', 1),
                                       ('a', 1),
                                       ('e', 1)])

    def test_validate_join_type(self):
        self._setup()
        with pytest.raises(TypeError, match='Did you accidentally call hstack'):
            table.hstack(self.t1, self.t2)

    def test_stack_same_table(self, operation_table_type):
        """
        From #2995, test that hstack'ing references to the same table has the
        expected output.
        """
        self._setup(operation_table_type)
        out = table.hstack([self.t1, self.t1])
        assert out.masked is False
        assert out.pformat() == ['a_1 b_1 a_2 b_2',
                                 '--- --- --- ---',
                                 '0.0 foo 0.0 foo',
                                 '1.0 bar 1.0 bar']

    def test_stack_rows(self, operation_table_type):
        self._setup(operation_table_type)
        out = table.hstack([self.t1[0], self.t2[1]])
        assert out.masked is False
        assert out.pformat() == ['a_1 b_1 a_2 b_2  c ',
                                 '--- --- --- --- ---',
                                 '0.0 foo 3.0 sez   5']

    def test_stack_columns(self, operation_table_type):
        self._setup(operation_table_type)
        out = table.hstack([self.t1, self.t2['c']])
        assert type(out['a']) is type(self.t1['a'])  # noqa
        assert type(out['b']) is type(self.t1['b'])  # noqa
        assert type(out['c']) is type(self.t2['c'])  # noqa
        assert out.pformat() == [' a   b   c ',
                                 '--- --- ---',
                                 '0.0 foo   4',
                                 '1.0 bar   5']

    def test_table_meta_merge(self, operation_table_type):
        self._setup(operation_table_type)
        out = table.hstack([self.t1, self.t2, self.t4], join_type='inner')
        assert out.meta == self.meta_merge

    def test_table_meta_merge_conflict(self, operation_table_type):
        self._setup(operation_table_type)

        with pytest.warns(metadata.MergeConflictWarning) as w:
            out = table.hstack([self.t1, self.t5], join_type='inner')
        assert len(w) == 2

        assert out.meta == self.t5.meta

        with pytest.warns(metadata.MergeConflictWarning) as w:
            out = table.hstack([self.t1, self.t5], join_type='inner', metadata_conflicts='warn')
        assert len(w) == 2

        assert out.meta == self.t5.meta

        out = table.hstack([self.t1, self.t5], join_type='inner', metadata_conflicts='silent')

        assert out.meta == self.t5.meta

        with pytest.raises(MergeConflictError):
            out = table.hstack([self.t1, self.t5], join_type='inner', metadata_conflicts='error')

        with pytest.raises(ValueError):
            out = table.hstack([self.t1, self.t5], join_type='inner', metadata_conflicts='nonsense')

    def test_bad_input_type(self, operation_table_type):
        self._setup(operation_table_type)
        with pytest.raises(ValueError):
            table.hstack([])
        with pytest.raises(TypeError):
            table.hstack(1)
        with pytest.raises(TypeError):
            table.hstack([self.t2, 1])
        with pytest.raises(ValueError):
            table.hstack([self.t1, self.t2], join_type='invalid join type')

    def test_stack_basic(self, operation_table_type):
        self._setup(operation_table_type)
        t1 = self.t1
        t2 = self.t2
        t3 = self.t3
        t4 = self.t4

        out = table.hstack([t1, t2], join_type='inner')
        assert out.masked is False
        assert type(out) is operation_table_type
        assert type(out['a_1']) is type(t1['a'])  # noqa
        assert type(out['b_1']) is type(t1['b'])  # noqa
        assert type(out['a_2']) is type(t2['a'])  # noqa
        assert type(out['b_2']) is type(t2['b'])  # noqa
        assert out.pformat() == ['a_1 b_1 a_2 b_2  c ',
                                 '--- --- --- --- ---',
                                 '0.0 foo 2.0 pez   4',
                                 '1.0 bar 3.0 sez   5']

        # stacking as a list gives same result
        out_list = table.hstack([t1, t2], join_type='inner')
        assert out.pformat() == out_list.pformat()

        out = table.hstack([t1, t2], join_type='outer')
        assert out.pformat() == out_list.pformat()

        out = table.hstack([t1, t2, t3, t4], join_type='outer')
        assert out.masked is False
        assert out.pformat() == ['a_1 b_1 a_2 b_2  c   d   e   f   g ',
                                 '--- --- --- --- --- --- --- --- ---',
                                 '0.0 foo 2.0 pez   4 4.0   7 0.0 foo',
                                 '1.0 bar 3.0 sez   5 5.0   8 1.0 bar',
                                 ' --  --  --  --  -- 6.0   9  --  --']

        out = table.hstack([t1, t2, t3, t4], join_type='inner')
        assert out.masked is False
        assert out.pformat() == ['a_1 b_1 a_2 b_2  c   d   e   f   g ',
                                 '--- --- --- --- --- --- --- --- ---',
                                 '0.0 foo 2.0 pez   4 4.0   7 0.0 foo',
                                 '1.0 bar 3.0 sez   5 5.0   8 1.0 bar']

    def test_stack_incompatible(self, operation_table_type):
        self._setup(operation_table_type)
        # For join_type exact, which will fail here because n_rows
        # does not match
        with pytest.raises(TableMergeError):
            table.hstack([self.t1, self.t3], join_type='exact')

    def test_hstack_one_masked(self, operation_table_type):
        if operation_table_type is QTable:
            pytest.xfail()
        self._setup(operation_table_type)
        t1 = self.t1
        t2 = operation_table_type(t1, copy=True, masked=True)
        t2.meta.clear()
        t2['b'].mask[1] = True
        out = table.hstack([t1, t2])
        assert out.pformat() == ['a_1 b_1 a_2 b_2',
                                 '--- --- --- ---',
                                 '0.0 foo 0.0 foo',
                                 '1.0 bar 1.0  --']

    def test_table_col_rename(self, operation_table_type):
        self._setup(operation_table_type)
        out = table.hstack([self.t1, self.t2], join_type='inner',
                           uniq_col_name='{table_name}_{col_name}',
                           table_names=('left', 'right'))
        assert out.masked is False
        assert out.pformat() == ['left_a left_b right_a right_b  c ',
                                 '------ ------ ------- ------- ---',
                                 '   0.0    foo     2.0     pez   4',
                                 '   1.0    bar     3.0     sez   5']

    def test_col_meta_merge(self, operation_table_type):
        self._setup(operation_table_type)
        t1 = self.t1
        t3 = self.t3[:2]
        t4 = self.t4

        # Just set a bunch of meta and make sure it is the same in output
        meta1 = OrderedDict([('b', [1, 2]), ('c', {'a': 1}), ('d', 1)])
        t1['a'].unit = 'cm'
        t1['b'].info.description = 't1_b'
        t4['f'].info.format = '%6s'
        t1['b'].info.meta.update(meta1)
        t3['d'].info.meta.update(OrderedDict([('b', [3, 4]), ('c', {'b': 1}), ('a', 1)]))
        t4['g'].info.meta.update(OrderedDict([('b', [5, 6]), ('c', {'c': 1}), ('e', 1)]))
        t3['e'].info.meta.update(OrderedDict([('b', [3, 4]), ('c', {'b': 1}), ('a', 1)]))
        t3['d'].unit = 'm'
        t3['d'].info.format = '%6s'
        t3['d'].info.description = 't3_c'

        out = table.hstack([t1, t3, t4], join_type='exact')

        for t in [t1, t3, t4]:
            for name in t.colnames:
                for attr in ('meta', 'unit', 'format', 'description'):
                    assert getattr(out[name].info, attr) == getattr(t[name].info, attr)

        # Make sure we got a copy of meta, not ref
        t1['b'].info.meta['b'] = None
        assert out['b'].info.meta['b'] == [1, 2]

    def test_hstack_one_table(self, operation_table_type):
        self._setup(operation_table_type)
        """Regression test for issue #3313"""
        assert (self.t1 == table.hstack(self.t1)).all()
        assert (self.t1 == table.hstack([self.t1])).all()

    def test_mixin_functionality(self, mixin_cols):
        col1 = mixin_cols['m']
        col2 = col1[2:4]  # Shorter version of col1
        t1 = table.QTable([col1])
        t2 = table.QTable([col2])

        cls_name = type(col1).__name__

        out = table.hstack([t1, t2], join_type='inner')
        assert type(out['col0_1']) is type(out['col0_2'])  # noqa
        assert len(out) == len(col2)

        # Check that columns are as expected.
        if cls_name == 'SkyCoord':
            assert skycoord_equal(out['col0_1'], col1[:len(col2)])
            assert skycoord_equal(out['col0_2'], col2)
        elif 'Repr' in cls_name or 'Diff' in cls_name:
            assert np.all(representation_equal(out['col0_1'], col1[:len(col2)]))
            assert np.all(representation_equal(out['col0_2'], col2))
        else:
            assert np.all(out['col0_1'] == col1[:len(col2)])
            assert np.all(out['col0_2'] == col2)

        # Time class supports masking, all other mixins do not
        if isinstance(col1, (Time, TimeDelta, Quantity)):
            out = table.hstack([t1, t2], join_type='outer')
            assert len(out) == len(t1)
            assert np.all(out['col0_1'] == col1)
            assert np.all(out['col0_2'][:len(col2)] == col2)
            assert check_mask(out['col0_2'], [False, False, True, True])

            # check directly stacking mixin columns:
            out2 = table.hstack([t1, t2['col0']], join_type='outer')
            assert np.all(out['col0_1'] == out2['col0_1'])
            assert np.all(out['col0_2'] == out2['col0_2'])
        else:
            with pytest.raises(NotImplementedError) as err:
                table.hstack([t1, t2], join_type='outer')
            assert 'hstack requires masking' in str(err.value)


def test_unique(operation_table_type):
    t = operation_table_type.read(
        [' a b  c  d',
         ' 2 b 7.0 0',
         ' 1 c 3.0 5',
         ' 2 b 6.0 2',
         ' 2 a 4.0 3',
         ' 1 a 1.0 7',
         ' 2 b 5.0 1',
         ' 0 a 0.0 4',
         ' 1 a 2.0 6',
         ' 1 c 3.0 5',
         ], format='ascii')

    tu = operation_table_type(np.sort(t[:-1]))

    t_all = table.unique(t)
    assert sort_eq(t_all.pformat(), tu.pformat())
    t_s = t.copy()
    del t_s['b', 'c', 'd']
    t_all = table.unique(t_s)
    assert sort_eq(t_all.pformat(), [' a ',
                                     '---',
                                     '  0',
                                     '  1',
                                     '  2'])

    key1 = 'a'
    t1a = table.unique(t, key1)
    assert sort_eq(t1a.pformat(), [' a   b   c   d ',
                                   '--- --- --- ---',
                                   '  0   a 0.0   4',
                                   '  1   c 3.0   5',
                                   '  2   b 7.0   0'])
    t1b = table.unique(t, key1, keep='last')
    assert sort_eq(t1b.pformat(), [' a   b   c   d ',
                                   '--- --- --- ---',
                                   '  0   a 0.0   4',
                                   '  1   c 3.0   5',
                                   '  2   b 5.0   1'])
    t1c = table.unique(t, key1, keep='none')
    assert sort_eq(t1c.pformat(), [' a   b   c   d ',
                                   '--- --- --- ---',
                                   '  0   a 0.0   4'])

    key2 = ['a', 'b']
    t2a = table.unique(t, key2)
    assert sort_eq(t2a.pformat(), [' a   b   c   d ',
                                   '--- --- --- ---',
                                   '  0   a 0.0   4',
                                   '  1   a 1.0   7',
                                   '  1   c 3.0   5',
                                   '  2   a 4.0   3',
                                   '  2   b 7.0   0'])

    t2b = table.unique(t, key2, keep='last')
    assert sort_eq(t2b.pformat(), [' a   b   c   d ',
                                   '--- --- --- ---',
                                   '  0   a 0.0   4',
                                   '  1   a 2.0   6',
                                   '  1   c 3.0   5',
                                   '  2   a 4.0   3',
                                   '  2   b 5.0   1'])
    t2c = table.unique(t, key2, keep='none')
    assert sort_eq(t2c.pformat(), [' a   b   c   d ',
                                   '--- --- --- ---',
                                   '  0   a 0.0   4',
                                   '  2   a 4.0   3'])

    key2 = ['a', 'a']
    with pytest.raises(ValueError) as exc:
        t2a = table.unique(t, key2)
    assert exc.value.args[0] == "duplicate key names"

    with pytest.raises(ValueError) as exc:
        table.unique(t, key2, keep=True)
    assert exc.value.args[0] == (
        "'keep' should be one of 'first', 'last', 'none'")

    t1_m = operation_table_type(t1a, masked=True)
    t1_m['a'].mask[1] = True

    with pytest.raises(ValueError) as exc:
        t1_mu = table.unique(t1_m)
    assert exc.value.args[0] == (
        "cannot use columns with masked values as keys; "
        "remove column 'a' from keys and rerun unique()")

    t1_mu = table.unique(t1_m, silent=True)
    assert t1_mu.masked is False
    assert t1_mu.pformat() == [' a   b   c   d ',
                               '--- --- --- ---',
                               '  0   a 0.0   4',
                               '  2   b 7.0   0',
                               ' --   c 3.0   5']

    with pytest.raises(ValueError):
        t1_mu = table.unique(t1_m, silent=True, keys='a')

    t1_m = operation_table_type(t, masked=True)
    t1_m['a'].mask[1] = True
    t1_m['d'].mask[3] = True

    # Test that multiple masked key columns get removed in the correct
    # order
    t1_mu = table.unique(t1_m, keys=['d', 'a', 'b'], silent=True)
    assert t1_mu.masked is False
    assert t1_mu.pformat() == [' a   b   c   d ',
                               '--- --- --- ---',
                               '  2   a 4.0  --',
                               '  2   b 7.0   0',
                               ' --   c 3.0   5']


def test_vstack_bytes(operation_table_type):
    """
    Test for issue #5617 when vstack'ing bytes columns in Py3.
    This is really an upstream numpy issue numpy/numpy/#8403.
    """
    t = operation_table_type([[b'a']], names=['a'])
    assert t['a'].itemsize == 1

    t2 = table.vstack([t, t])
    assert len(t2) == 2
    assert t2['a'].itemsize == 1


def test_vstack_unicode():
    """
    Test for problem related to issue #5617 when vstack'ing *unicode*
    columns.  In this case the character size gets multiplied by 4.
    """
    t = table.Table([['a']], names=['a'])
    assert t['a'].itemsize == 4  # 4-byte / char for U dtype

    t2 = table.vstack([t, t])
    assert len(t2) == 2
    assert t2['a'].itemsize == 4


def test_join_mixins_time_quantity():
    """
    Test for table join using non-ndarray key columns.
    """
    tm1 = Time([2, 1, 2], format='cxcsec')
    q1 = [2, 1, 1] * u.m
    idx1 = [1, 2, 3]
    tm2 = Time([2, 3], format='cxcsec')
    q2 = [2, 3] * u.m
    idx2 = [10, 20]
    t1 = Table([tm1, q1, idx1], names=['tm', 'q', 'idx'])
    t2 = Table([tm2, q2, idx2], names=['tm', 'q', 'idx'])
    # Output:
    #
    # <Table length=4>
    #         tm            q    idx_1 idx_2
    #                       m
    #       object       float64 int64 int64
    # ------------------ ------- ----- -----
    # 0.9999999999969589     1.0     2    --
    #   2.00000000000351     1.0     3    --
    #   2.00000000000351     2.0     1    10
    #  3.000000000000469     3.0    --    20

    t12 = table.join(t1, t2, join_type='outer', keys=['tm', 'q'])
    # Key cols are lexically sorted
    assert np.all(t12['tm'] == Time([1, 2, 2, 3], format='cxcsec'))
    assert np.all(t12['q'] == [1, 1, 2, 3] * u.m)
    assert np.all(t12['idx_1'] == np.ma.array([2, 3, 1, 0], mask=[0, 0, 0, 1]))
    assert np.all(t12['idx_2'] == np.ma.array([0, 0, 10, 20], mask=[1, 1, 0, 0]))


def test_join_mixins_not_sortable():
    """
    Test for table join using non-ndarray key columns that are not sortable.
    """
    sc = SkyCoord([1, 2], [3, 4], unit='deg,deg')
    t1 = Table([sc, [1, 2]], names=['sc', 'idx1'])
    t2 = Table([sc, [10, 20]], names=['sc', 'idx2'])

    with pytest.raises(TypeError, match='one or more key columns are not sortable'):
        table.join(t1, t2, keys='sc')


def test_join_non_1d_key_column():
    c1 = [[1, 2], [3, 4]]
    c2 = [1, 2]
    t1 = Table([c1, c2], names=['a', 'b'])
    t2 = t1.copy()
    with pytest.raises(ValueError, match="key column 'a' must be 1-d"):
        table.join(t1, t2, keys='a')


def test_argsort_time_column():
    """Regression test for #10823."""
    times = Time(['2016-01-01', '2018-01-01', '2017-01-01'])
    t = Table([times], names=['time'])
    i = t.argsort('time')
    assert np.all(i == times.argsort())


def test_sort_indexed_table():
    """Test fix for #9473 and #6545 - and another regression test for #10823."""
    t = Table([[1, 3, 2], [6, 4, 5]], names=('a', 'b'))
    t.add_index('a')
    t.sort('a')
    assert np.all(t['a'] == [1, 2, 3])
    assert np.all(t['b'] == [6, 5, 4])
    t.sort('b')
    assert np.all(t['b'] == [4, 5, 6])
    assert np.all(t['a'] == [3, 2, 1])

    times = ['2016-01-01', '2018-01-01', '2017-01-01']
    tm = Time(times)
    t2 = Table([tm, [3, 2, 1]], names=['time', 'flux'])
    t2.sort('flux')
    assert np.all(t2['flux'] == [1, 2, 3])
    t2.sort('time')
    assert np.all(t2['flux'] == [3, 1, 2])
    assert np.all(t2['time'] == tm[[0, 2, 1]])

    # Using the table as a TimeSeries implicitly sets the index, so
    # this test is a bit different from the above.
    from astropy.timeseries import TimeSeries
    ts = TimeSeries(time=times)
    ts['flux'] = [3, 2, 1]
    ts.sort('flux')
    assert np.all(ts['flux'] == [1, 2, 3])
    ts.sort('time')
    assert np.all(ts['flux'] == [3, 1, 2])
    assert np.all(ts['time'] == tm[[0, 2, 1]])


def test_get_out_class():
    c = table.Column([1, 2])
    mc = table.MaskedColumn([1, 2])
    q = [1, 2] * u.m

    assert _get_out_class([c, mc]) is mc.__class__
    assert _get_out_class([mc, c]) is mc.__class__
    assert _get_out_class([c, c]) is c.__class__
    assert _get_out_class([c]) is c.__class__

    with pytest.raises(ValueError):
        _get_out_class([c, q])

    with pytest.raises(ValueError):
        _get_out_class([q, c])


def test_masking_required_exception():
    """
    Test that outer join, hstack and vstack fail for a mixin column which
    does not support masking.
    """
    col = table.NdarrayMixin([0, 1, 2, 3])
    t1 = table.QTable([[1, 2, 3, 4], col], names=['a', 'b'])
    t2 = table.QTable([[1, 2], col[:2]], names=['a', 'c'])

    with pytest.raises(NotImplementedError) as err:
        table.vstack([t1, t2], join_type='outer')
    assert 'vstack unavailable' in str(err.value)

    with pytest.raises(NotImplementedError) as err:
        table.hstack([t1, t2], join_type='outer')
    assert 'hstack requires masking' in str(err.value)

    with pytest.raises(NotImplementedError) as err:
        table.join(t1, t2, join_type='outer')
    assert 'join requires masking' in str(err.value)


def test_stack_columns():
    c = table.Column([1, 2])
    mc = table.MaskedColumn([1, 2])
    q = [1, 2] * u.m
    time = Time(['2001-01-02T12:34:56', '2001-02-03T00:01:02'])
    sc = SkyCoord([1, 2], [3, 4], unit='deg')
    cq = table.Column([11, 22], unit=u.m)

    t = table.hstack([c, q])
    assert t.__class__ is table.QTable
    assert t.masked is False
    t = table.hstack([q, c])
    assert t.__class__ is table.QTable
    assert t.masked is False

    t = table.hstack([mc, q])
    assert t.__class__ is table.QTable
    assert t.masked is False

    t = table.hstack([c, mc])
    assert t.__class__ is table.Table
    assert t.masked is False

    t = table.vstack([q, q])
    assert t.__class__ is table.QTable

    t = table.vstack([c, c])
    assert t.__class__ is table.Table

    t = table.hstack([c, time])
    assert t.__class__ is table.Table
    t = table.hstack([c, sc])
    assert t.__class__ is table.Table
    t = table.hstack([q, time, sc])
    assert t.__class__ is table.QTable

    with pytest.raises(ValueError):
        table.vstack([c, q])

    with pytest.raises(ValueError):
        t = table.vstack([q, cq])


def test_mixin_join_regression():
    # This used to trigger a ValueError:
    # ValueError: NumPy boolean array indexing assignment cannot assign
    # 6 input values to the 4 output values where the mask is true

    t1 = QTable()
    t1['index'] = [1, 2, 3, 4, 5]
    t1['flux1'] = [2, 3, 2, 1, 1] * u.Jy
    t1['flux2'] = [2, 3, 2, 1, 1] * u.Jy

    t2 = QTable()
    t2['index'] = [3, 4, 5, 6]
    t2['flux1'] = [2, 1, 1, 3] * u.Jy
    t2['flux2'] = [2, 1, 1, 3] * u.Jy

    t12 = table.join(t1, t2, keys=('index', 'flux1', 'flux2'), join_type='outer')

    assert len(t12) == 6
