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/** @file row/row0ext.cc
 Caching of externally stored column prefixes

 Created September 2006 Marko Makela
 *******************************************************/

#include "row0ext.h"
#include "lob0lob.h"

#ifdef UNIV_NONINL
#include "row0ext.ic"
#endif

#include "btr0cur.h"

/** Fills the column prefix cache of an externally stored column.
@param[in]      index           clustered index from which LOB is fetched.
@param[in,out]  ext             column prefix cache
@param[in]      i               index of ext->ext[]
@param[in]      page_size       page size
@param[in]      dfield          data field
@param[in]      is_sdi          true for SDI Index */
static void row_ext_cache_fill(const dict_index_t *index, row_ext_t *ext,
                               ulint i, const page_size_t &page_size,
                               IF_DEBUG(bool is_sdi, ) const dfield_t *dfield) {
  const byte *field = static_cast<const byte *>(dfield_get_data(dfield));
  ulint f_len = dfield_get_len(dfield);
  byte *buf = ext->buf + i * ext->max_len;
  lob::ref_t blobref(dfield->blobref());

  ut_ad(ext->max_len > 0);
  ut_ad(i < ext->n_ext);
  ut_ad(dfield_is_ext(dfield));
  ut_a(f_len >= BTR_EXTERN_FIELD_REF_SIZE);

  if (blobref.is_null()) {
    /* The BLOB pointer is not set: we cannot fetch it */
    ext->len[i] = 0;
  } else {
    if (ext->max_len == REC_VERSION_56_MAX_INDEX_COL_LEN &&
        f_len > BTR_EXTERN_FIELD_REF_SIZE) {
      /* In this case, the field is in B format or beyond,
      (refer to the definition of row_ext_t.max_len)
      and the field is already fill with prefix, otherwise
      f_len would be BTR_EXTERN_FIELD_REF_SIZE.
      So there is no need to re-read the prefix externally,
      but just copy the local prefix to buf. Please note
      if the ext->len[i] is zero, it means an error
      as above. */
      memcpy(buf, field, f_len - BTR_EXTERN_FIELD_REF_SIZE);
      ext->len[i] = f_len - BTR_EXTERN_FIELD_REF_SIZE;
    } else {
      /* Fetch at most ext->max_len of the column.
      The column should be non-empty.  However,
      trx_rollback_or_clean_all_recovered() may try to
      access a half-deleted BLOB if the server previously
      crashed during the execution of
      btr_free_externally_stored_field(). */
      ext->len[i] = lob::btr_copy_externally_stored_field_prefix_func(
          nullptr, index, buf, ext->max_len, page_size, field,
          IF_DEBUG(is_sdi, ) f_len);
    }
  }
}

/** Creates a cache of column prefixes of externally stored columns.
@param[in]      index   the index to which LOB belongs.
@param[in]      n_ext   number of externally stored columns
@param[in]      ext     col_no's of externally stored columns in the InnoDB
table object, as reported by dict_col_get_no(); NOT relative to the records
in the clustered index
@param[in]      flags   table->flags
@param[in]      tuple   data tuple containing the field references of the
externally stored columns; must be indexed by col_no; the clustered index record
must be covered by a lock or a page latch to prevent deletion (rollback
or purge)
@param[in]      is_sdi  true for SDI Indexes
@param[in,out]  heap    heap where created
@return own: column prefix cache */
row_ext_t *row_ext_create_func(const dict_index_t *index, ulint n_ext,
                               const ulint *ext, uint32_t flags,
                               const dtuple_t *tuple,
                               IF_DEBUG(bool is_sdi, ) mem_heap_t *heap) {
  ulint i;
  const page_size_t &page_size = dict_tf_get_page_size(flags);

  /* LOBs are available in clustered index only. */
  ut_ad(index->is_clustered());

  row_ext_t *ret;

  ut_ad(n_ext > 0);

  ret = static_cast<row_ext_t *>(
      mem_heap_alloc(heap, (sizeof *ret) + (n_ext - 1) * sizeof ret->len));

  ret->index = index;
  ret->n_ext = n_ext;
  ret->ext = ext;
  ret->max_len = DICT_MAX_FIELD_LEN_BY_FORMAT_FLAG(flags);
  ret->page_size.copy_from(page_size);

  ret->buf = static_cast<byte *>(mem_heap_alloc(heap, n_ext * ret->max_len));

#ifdef UNIV_DEBUG
  memset(ret->buf, 0xaa, n_ext * ret->max_len);
  UNIV_MEM_ALLOC(ret->buf, n_ext * ret->max_len);
#endif

  /* Fetch the BLOB prefixes */
  for (i = 0; i < n_ext; i++) {
    const dfield_t *dfield;

    dfield = dtuple_get_nth_field(tuple, ext[i]);
    row_ext_cache_fill(index, ret, i, page_size, IF_DEBUG(is_sdi, ) dfield);
  }

  return (ret);
}
