diff --git a/mysql-test/r/func_group.result b/mysql-test/r/func_group.result index 3d989ad1730..94147640cde 100644 --- a/mysql-test/r/func_group.result +++ b/mysql-test/r/func_group.result @@ -1477,3 +1477,47 @@ COUNT(*) SET SQL_MODE=default; DROP TABLE t1; End of 5.0 tests +# +# BUG#47280 - strange results from count(*) with order by multiple +# columns without where/group +# +# +# Initialize test +# +CREATE TABLE t1 ( +pk INT NOT NULL, +i INT, +PRIMARY KEY (pk) +); +INSERT INTO t1 VALUES (1,11),(2,12),(3,13); +# +# Start test +# All the following queries shall return 1 record +# + +# Masking all correct values {11...13} for column i in this result. +SELECT MAX(pk) as max, i +FROM t1 +ORDER BY max; +max i +3 # + +EXPLAIN +SELECT MAX(pk) as max, i +FROM t1 +ORDER BY max; +id select_type table type possible_keys key key_len ref rows Extra +1 SIMPLE t1 ALL NULL NULL NULL NULL 3 Using temporary + +# Only 11 is correct for collumn i in this result +SELECT MAX(pk) as max, i +FROM t1 +WHERE pk<2 +ORDER BY max; +max i +1 11 +# +# Cleanup +# +DROP TABLE t1; +End of 5.1 tests diff --git a/mysql-test/t/func_group.test b/mysql-test/t/func_group.test index b0a3d0feb79..6e39795a5d6 100644 --- a/mysql-test/t/func_group.test +++ b/mysql-test/t/func_group.test @@ -1006,3 +1006,51 @@ DROP TABLE t1; ### --echo End of 5.0 tests + +--echo # +--echo # BUG#47280 - strange results from count(*) with order by multiple +--echo # columns without where/group +--echo # + +--echo # +--echo # Initialize test +--echo # + +CREATE TABLE t1 ( + pk INT NOT NULL, + i INT, + PRIMARY KEY (pk) +); +INSERT INTO t1 VALUES (1,11),(2,12),(3,13); + +--echo # +--echo # Start test +--echo # All the following queries shall return 1 record +--echo # + +--echo +--echo # Masking all correct values {11...13} for column i in this result. +--replace_column 2 # +SELECT MAX(pk) as max, i +FROM t1 +ORDER BY max; + +--echo +EXPLAIN +SELECT MAX(pk) as max, i +FROM t1 +ORDER BY max; + +--echo +--echo # Only 11 is correct for collumn i in this result +SELECT MAX(pk) as max, i +FROM t1 +WHERE pk<2 +ORDER BY max; + +--echo # +--echo # Cleanup +--echo # +DROP TABLE t1; + +--echo End of 5.1 tests diff --git a/sql/opt_sum.cc b/sql/opt_sum.cc index 8e7265ba1ad..e009cf1ca9f 100644 --- a/sql/opt_sum.cc +++ b/sql/opt_sum.cc @@ -97,7 +97,8 @@ static ulonglong get_exact_record_count(TABLE_LIST *tables) @note This function is only called for queries with sum functions and no - GROUP BY part. + GROUP BY part. This means that the result set shall contain a single + row only @retval 0 no errors diff --git a/sql/sql_class.h b/sql/sql_class.h index 024a6587b43..922e960c805 100644 --- a/sql/sql_class.h +++ b/sql/sql_class.h @@ -2647,7 +2647,32 @@ public: MI_COLUMNDEF *recinfo,*start_recinfo; KEY *keyinfo; ha_rows end_write_records; - uint field_count,sum_func_count,func_count; + /** + Number of normal fields in the query, including those referred to + from aggregate functions. Hence, "SELECT `field1`, + SUM(`field2`) from t1" sets this counter to 2. + + @see count_field_types + */ + uint field_count; + /** + Number of fields in the query that have functions. Includes both + aggregate functions (e.g., SUM) and non-aggregates (e.g., RAND). + Also counts functions referred to from aggregate functions, i.e., + "SELECT SUM(RAND())" sets this counter to 2. + + @see count_field_types + */ + uint func_count; + /** + Number of fields in the query that have aggregate functions. Note + that the optimizer may choose to optimize away these fields by + replacing them with constants, in which case sum_func_count will + need to be updated. + + @see opt_sum_query, count_field_types + */ + uint sum_func_count; uint hidden_field_count; uint group_parts,group_length,group_null_parts; uint quick_group; diff --git a/sql/sql_select.cc b/sql/sql_select.cc index 9dacb2c2ce4..02e52e0c518 100644 --- a/sql/sql_select.cc +++ b/sql/sql_select.cc @@ -644,8 +644,11 @@ JOIN::prepare(Item ***rref_pointer_array, this->group= group_list != 0; unit= unit_arg; + if (tmp_table_param.sum_func_count && !group_list) + implicit_grouping= TRUE; + #ifdef RESTRICTED_GROUP - if (sum_func_count && !group_list && (func_count || field_count)) + if (implicit_grouping) { my_message(ER_WRONG_SUM_SELECT,ER(ER_WRONG_SUM_SELECT),MYF(0)); goto err; @@ -881,15 +884,23 @@ JOIN::optimize() } #endif - /* Optimize count(*), min() and max() */ - if (tables_list && tmp_table_param.sum_func_count && ! group_list) + /* + Try to optimize count(*), min() and max() to const fields if + there is implicit grouping (aggregate functions but no + group_list). In this case, the result set shall only contain one + row. + */ + if (tables_list && implicit_grouping) { int res; /* opt_sum_query() returns HA_ERR_KEY_NOT_FOUND if no rows match to the WHERE conditions, - or 1 if all items were resolved, + or 1 if all items were resolved (optimized away), or 0, or an error number HA_ERR_... + + If all items were resolved by opt_sum_query, there is no need to + open any tables. */ if ((res=opt_sum_query(select_lex->leaf_tables, all_fields, conds))) { @@ -2024,7 +2035,7 @@ JOIN::exec() count_field_types(select_lex, &curr_join->tmp_table_param, *curr_all_fields, 0); - if (curr_join->group || curr_join->tmp_table_param.sum_func_count || + if (curr_join->group || curr_join->implicit_grouping || (procedure && (procedure->flags & PROC_GROUP))) { if (make_group_fields(this, curr_join)) @@ -10811,6 +10822,12 @@ Next_select_func setup_end_select_func(JOIN *join) } else { + /* + Choose method for presenting result to user. Use end_send_group + if the query requires grouping (has a GROUP BY clause and/or one or + more aggregate functions). Use end_send if the query should not + be grouped. + */ if ((join->sort_and_group || (join->procedure && join->procedure->flags & PROC_GROUP)) && !tmp_tbl->precomputed_group_by) diff --git a/sql/sql_select.h b/sql/sql_select.h index 3f06b402638..92356a4c96f 100644 --- a/sql/sql_select.h +++ b/sql/sql_select.h @@ -278,7 +278,14 @@ public: TABLE **table,**all_tables,*sort_by_table; uint tables,const_tables; uint send_group_parts; - bool sort_and_group,first_record,full_join,group, no_field_update; + /** + Indicates that grouping will be performed on the result set during + query execution. This field belongs to query execution. + + @see make_group_fields, alloc_group_fields, JOIN::exec + */ + bool sort_and_group; + bool first_record,full_join,group, no_field_update; bool do_send_rows; /** TRUE when we want to resume nested loop iterations when @@ -428,6 +435,7 @@ public: tables= 0; const_tables= 0; join_list= 0; + implicit_grouping= FALSE; sort_and_group= 0; first_record= 0; do_send_rows= 1; @@ -533,6 +541,11 @@ public: select_lex == unit->fake_select_lex)); } private: + /** + TRUE if the query contains an aggregate function but has no GROUP + BY clause. + */ + bool implicit_grouping; bool make_simple_join(JOIN *join, TABLE *tmp_table); };