row0sel.c:
Add more comments to row_search_for_mysql() and remove the ugly double use of the variable rec in that function
This commit is contained in:
heikki@hundin.mysql.fi
parent
cfdb60b6b2
commit
92f034332a
@ -2724,7 +2724,9 @@ row_sel_get_clust_rec_for_mysql(
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if (trx->isolation_level > TRX_ISO_READ_UNCOMMITTED
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&& !lock_clust_rec_cons_read_sees(clust_rec, clust_index,
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*offsets, trx->read_view)) {
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/* The following call returns 'offsets' associated with
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'old_vers' */
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err = row_sel_build_prev_vers_for_mysql(
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trx->read_view, clust_index,
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prebuilt, clust_rec,
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@ -3062,7 +3064,7 @@ row_search_for_mysql(
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dict_index_t* clust_index;
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que_thr_t* thr;
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rec_t* rec;
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rec_t* index_rec;
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rec_t* result_rec;
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rec_t* clust_rec;
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rec_t* old_vers;
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ulint err = DB_SUCCESS;
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@ -3548,16 +3550,20 @@ rec_loop:
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if (comp) {
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next_offs = rec_get_next_offs(rec, TRUE);
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if (UNIV_UNLIKELY(next_offs < PAGE_NEW_SUPREMUM)) {
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goto wrong_offs;
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}
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} else {
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next_offs = rec_get_next_offs(rec, FALSE);
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if (UNIV_UNLIKELY(next_offs < PAGE_OLD_SUPREMUM)) {
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goto wrong_offs;
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}
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}
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if (UNIV_UNLIKELY(next_offs >= UNIV_PAGE_SIZE - PAGE_DIR)) {
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wrong_offs:
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wrong_offs:
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if (srv_force_recovery == 0 || moves_up == FALSE) {
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ut_print_timestamp(stderr);
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buf_page_print(buf_frame_align(rec));
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@ -3600,6 +3606,9 @@ rec_loop:
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goto next_rec;
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}
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}
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/*-------------------------------------------------------------*/
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/* Calculate the 'offsets' associated with 'rec' */
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offsets = rec_get_offsets(rec, index, offsets, ULINT_UNDEFINED, &heap);
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@ -3620,8 +3629,6 @@ rec_loop:
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}
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}
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/*-------------------------------------------------------------*/
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/* Note that we cannot trust the up_match value in the cursor at this
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place because we can arrive here after moving the cursor! Thus
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we have to recompare rec and search_tuple to determine if they
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@ -3768,6 +3775,8 @@ no_gap_lock:
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&& !lock_clust_rec_cons_read_sees(rec, index,
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offsets, trx->read_view)) {
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/* The following call returns 'offsets'
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associated with 'old_vers' */
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err = row_sel_build_prev_vers_for_mysql(
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trx->read_view, clust_index,
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prebuilt, rec,
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@ -3796,8 +3805,6 @@ no_gap_lock:
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is necessary, because we can only get the undo
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information via the clustered index record. */
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/* Get the clustered index record if needed */
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index_rec = rec;
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ut_ad(index != clust_index);
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goto requires_clust_rec;
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@ -3807,7 +3814,7 @@ no_gap_lock:
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/* NOTE that at this point rec can be an old version of a clustered
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index record built for a consistent read. We cannot assume after this
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point that rec is on a buffer pool page. Functions like
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page_rec_is_comp() cannot be used then! */
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page_rec_is_comp() cannot be used! */
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if (UNIV_UNLIKELY(rec_get_deleted_flag(rec, comp))) {
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@ -3829,19 +3836,15 @@ no_gap_lock:
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goto next_rec;
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}
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/* Get the clustered index record if needed and if we did
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not do the search using the clustered index */
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index_rec = rec;
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/* Get the clustered index record if needed, if we did not do the
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search using the clustered index. */
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if (index != clust_index && prebuilt->need_to_access_clustered) {
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requires_clust_rec:
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/* Before and after this "if" block, "offsets" will be
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related to "rec", which may be in a secondary index "index" or
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the clustered index ("clust_index"). However, after this
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"if" block, "rec" may be pointing to
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"clust_rec" of "clust_index". */
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/* We use a 'goto' to the preceding label if a consistent
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read of a secondary index record requires us to look up old
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versions of the associated clustered index record. */
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ut_ad(rec_offs_validate(rec, index, offsets));
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@ -3849,6 +3852,10 @@ requires_clust_rec:
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clustered index record */
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mtr_has_extra_clust_latch = TRUE;
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/* The following call returns 'offsets' associated with
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'clust_rec'. Note that 'clust_rec' can be an old version
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built for a consistent read. */
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err = row_sel_get_clust_rec_for_mysql(prebuilt, index, rec,
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thr, &clust_rec,
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@ -3885,17 +3892,26 @@ requires_clust_rec:
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}
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if (prebuilt->need_to_access_clustered) {
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rec = clust_rec;
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result_rec = clust_rec;
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ut_ad(rec_offs_validate(rec, clust_index, offsets));
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} else {
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/* We used 'offsets' for the clust rec, recalculate
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them for 'rec' */
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offsets = rec_get_offsets(rec, index, offsets,
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ULINT_UNDEFINED, &heap);
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result_rec = rec;
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}
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} else {
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result_rec = rec;
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}
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/* We found a qualifying row */
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ut_ad(rec_offs_validate(rec,
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rec == clust_rec ? clust_index : index,
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/* We found a qualifying record 'result_rec'. At this point,
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'offsets' are associated with 'result_rec'. */
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ut_ad(rec_offs_validate(result_rec,
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result_rec != rec ? clust_index : index,
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offsets));
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if ((match_mode == ROW_SEL_EXACT
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@ -3916,8 +3932,8 @@ requires_clust_rec:
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not cache rows because there the cursor is a scrollable
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cursor. */
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row_sel_push_cache_row_for_mysql(prebuilt, rec, offsets);
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row_sel_push_cache_row_for_mysql(prebuilt, result_rec,
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offsets);
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if (prebuilt->n_fetch_cached == MYSQL_FETCH_CACHE_SIZE) {
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goto got_row;
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@ -3926,13 +3942,14 @@ requires_clust_rec:
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goto next_rec;
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} else {
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if (prebuilt->template_type == ROW_MYSQL_DUMMY_TEMPLATE) {
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memcpy(buf + 4, rec - rec_offs_extra_size(offsets),
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memcpy(buf + 4, result_rec
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- rec_offs_extra_size(offsets),
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rec_offs_size(offsets));
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mach_write_to_4(buf,
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rec_offs_extra_size(offsets) + 4);
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} else {
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if (!row_sel_store_mysql_rec(buf, prebuilt,
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rec, offsets)) {
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result_rec, offsets)) {
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err = DB_TOO_BIG_RECORD;
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goto lock_wait_or_error;
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@ -3940,15 +3957,18 @@ requires_clust_rec:
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}
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if (prebuilt->clust_index_was_generated) {
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if (rec != index_rec) {
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if (result_rec != rec) {
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offsets = rec_get_offsets(
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index_rec, index, offsets,
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rec, index, offsets,
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ULINT_UNDEFINED, &heap);
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}
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row_sel_store_row_id_to_prebuilt(prebuilt, index_rec,
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row_sel_store_row_id_to_prebuilt(prebuilt, rec,
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index, offsets);
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}
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}
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/* From this point on, 'offsets' are invalid. */
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got_row:
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/* We have an optimization to save CPU time: if this is a consistent
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read on a unique condition on the clustered index, then we do not
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@ -3999,7 +4019,7 @@ next_rec:
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if (moves_up) {
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if (UNIV_UNLIKELY(!btr_pcur_move_to_next(pcur, &mtr))) {
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not_moved:
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not_moved:
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btr_pcur_store_position(pcur, &mtr);
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if (match_mode != 0) {
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