diff options
Diffstat (limited to 'sql/sql_join_cache.cc')
| -rw-r--r-- | sql/sql_join_cache.cc | 88 |
1 files changed, 78 insertions, 10 deletions
diff --git a/sql/sql_join_cache.cc b/sql/sql_join_cache.cc index b8b4d491b84..1c36470f254 100644 --- a/sql/sql_join_cache.cc +++ b/sql/sql_join_cache.cc @@ -1650,7 +1650,7 @@ void JOIN_CACHE::get_record_by_pos(uchar *rec_ptr) } -/* +/* Get the match flag from the referenced record: the default implementation SYNOPSIS @@ -1662,6 +1662,7 @@ void JOIN_CACHE::get_record_by_pos(uchar *rec_ptr) get the match flag for the record pointed by the reference at the position rec_ptr. If the match flag is placed in one of the previous buffers the function first reaches the linked record fields in this buffer. + The function returns the value of the first encountered match flag. RETURN VALUE match flag for the record at the position rec_ptr @@ -1686,6 +1687,39 @@ enum JOIN_CACHE::Match_flag JOIN_CACHE::get_match_flag_by_pos(uchar *rec_ptr) /* + Get the match flag for the referenced record from specified join buffer + + SYNOPSIS + get_match_flag_by_pos_from_join_buffer() + rec_ptr position of the first field of the record in the join buffer + tab join table with join buffer where to look for the match flag + + DESCRIPTION + This default implementation of the get_match_flag_by_pos_from_join_buffer + method gets the match flag for the record pointed by the reference at the + position rec_ptr from the join buffer attached to the join table tab. + + RETURN VALUE + match flag for the record at the position rec_ptr from the join + buffer attached to the table tab. +*/ + +enum JOIN_CACHE::Match_flag +JOIN_CACHE::get_match_flag_by_pos_from_join_buffer(uchar *rec_ptr, + JOIN_TAB *tab) +{ + DBUG_ASSERT(tab->cache && tab->cache->with_match_flag); + for (JOIN_CACHE *cache= this; ; ) + { + if (cache->join_tab == tab) + return (enum Match_flag) rec_ptr[0]; + cache= cache->prev_cache; + rec_ptr= cache->get_rec_ref(rec_ptr); + } +} + + +/* Calculate the increment of the auxiliary buffer for a record write SYNOPSIS @@ -1955,6 +1989,10 @@ bool JOIN_CACHE::read_referenced_field(CACHE_FIELD *copy, If the record is skipped the value of 'pos' is set to point to the position right after the record. + NOTE + Currently this function is called only when generating null complemented + records for outer joins (=> only when join_tab->first_unmatched != NULL). + RETURN VALUE TRUE the match flag is set to MATCH_FOUND and the record has been skipped FALSE otherwise @@ -1967,7 +2005,9 @@ bool JOIN_CACHE::skip_if_matched() if (prev_cache) offset+= prev_cache->get_size_of_rec_offset(); /* Check whether the match flag is MATCH_FOUND */ - if (get_match_flag_by_pos(pos+offset) == MATCH_FOUND) + if (get_match_flag_by_pos_from_join_buffer(pos+offset, + join_tab->first_unmatched) == + MATCH_FOUND) { pos+= size_of_rec_len + get_rec_length(pos); return TRUE; @@ -1984,13 +2024,23 @@ bool JOIN_CACHE::skip_if_matched() DESCRIPTION This default implementation of the virtual function skip_if_not_needed_match - skips the next record from the join buffer if its match flag is not - MATCH_NOT_FOUND, and, either its value is MATCH_FOUND and join_tab is the - first inner table of an inner join, or, its value is MATCH_IMPOSSIBLE - and join_tab is the first inner table of an outer join. + skips the next record from the join when generating join extensions + for the records in the join buffer depending on the value of the match flag. + - In the case of a semi-nest the match flag may be in two states + {MATCH_NOT_FOUND, MATCH_FOUND}. The record is skipped if the flag is set + to MATCH_FOUND. + - In the case of a outer join nest when not_exists optimization is applied + the match may be in three states {MATCH_NOT_FOUND, MATCH_IMPOSSIBLE, + MATCH_FOUND. The record is skipped if the flag is set to MATCH_FOUND or + to MATCH_IMPOSSIBLE. + If the record is skipped the value of 'pos' is set to point to the position right after the record. + NOTE + Currently the function is called only when generating non-null complemented + extensions for records in the join buffer. + RETURN VALUE TRUE the record has to be skipped FALSE otherwise @@ -2001,11 +2051,19 @@ bool JOIN_CACHE::skip_if_not_needed_match() DBUG_ASSERT(with_length); enum Match_flag match_fl; uint offset= size_of_rec_len; + bool skip= FALSE; if (prev_cache) offset+= prev_cache->get_size_of_rec_offset(); - if ((match_fl= get_match_flag_by_pos(pos+offset)) != MATCH_NOT_FOUND && - (join_tab->check_only_first_match() == (match_fl == MATCH_FOUND)) ) + if (!join_tab->check_only_first_match()) + return FALSE; + + match_fl= get_match_flag_by_pos(pos+offset); + skip= join_tab->first_sj_inner_tab ? + match_fl == MATCH_FOUND : // the case of semi-join + match_fl != MATCH_NOT_FOUND; // the case of outer-join + + if (skip) { pos+= size_of_rec_len + get_rec_length(pos); return TRUE; @@ -2105,7 +2163,14 @@ enum_nested_loop_state JOIN_CACHE::join_records(bool skip_last) goto finish; } join_tab->not_null_compl= FALSE; - /* Prepare for generation of null complementing extensions */ + /* + Prepare for generation of null complementing extensions. + For all inner tables of the outer join operation for which + regular matches have been just found the field 'first_unmatched' + is set to point the the first inner table. After all null + complement rows are generated for this outer join this field + is set back to NULL. + */ for (tab= join_tab->first_inner; tab <= join_tab->last_inner; tab++) tab->first_unmatched= join_tab->first_inner; } @@ -2222,7 +2287,10 @@ enum_nested_loop_state JOIN_CACHE::join_matching_records(bool skip_last) int error; enum_nested_loop_state rc= NESTED_LOOP_OK; join_tab->table->null_row= 0; - bool check_only_first_match= join_tab->check_only_first_match(); + bool check_only_first_match= + join_tab->check_only_first_match() && + (!join_tab->first_inner || // semi-join case + join_tab->first_inner == join_tab->first_unmatched); // outer join case bool outer_join_first_inner= join_tab->is_first_inner_for_outer_join(); DBUG_ENTER("JOIN_CACHE::join_matching_records"); |