/**********************************************************************//**
Fetch a prefix of an externally stored column, for writing to the undo log
of an update or delete marking of a clustered index record.
@return ext_buf */
static
byte*
trx_undo_page_fetch_ext(
/*====================*/
byte* ext_buf, /*!< in: a buffer of
REC_MAX_INDEX_COL_LEN
+ BTR_EXTERN_FIELD_REF_SIZE */
ulint zip_size, /*!< compressed page size in bytes,
or 0 for uncompressed BLOB */
const byte* field, /*!< in: an externally stored column */
ulint* len) /*!< in: length of field;
out: used length of ext_buf */
{
/* Fetch the BLOB. */
ulint ext_len = btr_copy_externally_stored_field_prefix(
ext_buf, REC_MAX_INDEX_COL_LEN, zip_size, field, *len);
/* BLOBs should always be nonempty. */
ut_a(ext_len);
/* Append the BLOB pointer to the prefix. */
memcpy(ext_buf + ext_len,
field + *len - BTR_EXTERN_FIELD_REF_SIZE,
BTR_EXTERN_FIELD_REF_SIZE);
*len = ext_len + BTR_EXTERN_FIELD_REF_SIZE;
return(ext_buf);
}
/********************************************************************//**
Fills the column prefix cache of an externally stored column. */
static
void
row_ext_cache_fill(
/*===============*/
row_ext_t* ext, /*!< in/out: column prefix cache */
ulint i, /*!< in: index of ext->ext[] */
ulint zip_size,/*!< compressed page size in bytes, or 0 */
const dfield_t* dfield) /*!< in: data field */
{
const byte* field = dfield_get_data(dfield);
ulint f_len = dfield_get_len(dfield);
byte* buf = ext->buf + i * ext->max_len;
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 (UNIV_UNLIKELY(!memcmp(field_ref_zero,
field + f_len - BTR_EXTERN_FIELD_REF_SIZE,
BTR_EXTERN_FIELD_REF_SIZE))) {
/* The BLOB pointer is not set: we cannot fetch it */
ext->len[i] = 0;
} 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] = btr_copy_externally_stored_field_prefix(
buf, ext->max_len, zip_size, field, f_len);
}
}
