Only add indexed BLOBs to row_ext.
trx_undo_rec_get_partial_row(): Move the BLOB fetching to row_ext_create().
row_build(): Pass only those BLOBs to row_ext_create() that are referenced by
ordering columns of some indexes, similar to trx_undo_rec_get_partial_row().
row_ext_create(): Add the parameter "tuple". Move the implementation
from row0ext.ic to row0ext.c.
row_ext_lookup_ith(), row_ext_lookup(): Return a const pointer. Remove
the parameters "field" and "f_len". Make the row_ext_t* parameter const.
row_ext_t: Remove the field zip_size.
field_ref_zero[]: Declare in btr0types.h instead of btr0cur.h.
row_ext_lookup_low(): Rename to row_ext_cache_fill() and change the
signature.
only for those externally stored columns that occur in the ordering columns
of indexes. Prefetch the prefixes of those columns, because the clustered
index record and the BLOBs may have been deleted by the time when the
purge thread needs to read the BLOB prefixes.
row_ext_create(): Add the debug assertion ut_ad(ut_is_2pow(zip_size)).
inserted, uncommitted clustered index records when determining if a
secondary index record that contains a column prefix of an externally
stored column is referencing the clustered index record.
field_ref_zero[]: A BLOB pointer full of zero, for use in comparisons.
btr_copy_externally_stored_field_prefix(): Assert that the BLOB pointer is set.
row_ext_lookup_ith(), row_ext_lookup(), row_ext_lookup_low(): Document
that field_ref_zero is returned when the BLOB cannot be fetched.
row_ext_lookup_low(): Return field_ref_zero and *len = 0 when the
BLOB pointer is unset.
row_build_index_entry(): Return NULL when a needed BLOB pointer cannot
be dereferenced (row_ext_lookup returns field_ref_zero). Check the
return value for NULL in callers.
row_vers_impl_x_locked_off_kernel(): Avoid comparisons when
row_build_index_entry() returns NULL.
row_vers_old_has_index_entry(): Ignore records for which
row_build_index_entry() returns NULL. The entry should never be NULL
in rollback, but it may be NULL in purge.
row_merge_buf_add(): Assert that row_ext_lookup() does not return
field_ref_zero. The table will be locked during index creation.
in the clustered index to be smaller than the indexed prefix in secondary
indexes.
row_ext_lookup(): Return NULL if the column is not stored externally.
trx_undo_rec_get_partial_row(): row_build(): Add parameter row_ext_t** ext.
row_build_index_entry(): Add the parameter row_ext_t* ext.
Invoke row_ext_lookup() to fetch prefixes of externally stored columns.
upd_node_t, undo_node_t, purge_node_t: Add the field row_ext_t* ext.
This will be needed for fixing Bug #22496.
REC_MAX_INDEX_COL_LEN: New constant, copied from DICT_MAX_INDEX_COL_LEN.
row_ext_create(), row_ext_lookup(), row_ext_lookup_low(): New functions.
