WL#1972 "Evaluate HAVING before SELECT select-list"
- post-review changes sql/item.cc: - more/improved comments
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sql/item.cc
86
sql/item.cc
@ -1564,7 +1564,8 @@ resolve_ref_in_select_and_group(THD *thd, Item_ident *ref, SELECT_LEX *select)
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{
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if (select_ref != not_found_item && !ambiguous_fields)
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{
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if (*select_ref && !(*select_ref)->fixed)
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DBUG_ASSERT(*select_ref);
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if (! (*select_ref)->fixed)
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{
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my_error(ER_ILLEGAL_REFERENCE, MYF(0), ref->name,
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"forward reference in item list");
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@ -1582,6 +1583,58 @@ resolve_ref_in_select_and_group(THD *thd, Item_ident *ref, SELECT_LEX *select)
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}
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/*
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Resolve the name of a column reference.
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SYNOPSIS
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Item_field::fix_fields()
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thd [in] current thread
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tables [in] the tables in a FROM clause
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reference [in/out] view column if this item was resolved to a view column
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DESCRIPTION
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The method resolves the column reference represented by 'this' as a column
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present in one of: FROM clause, SELECT clause, GROUP BY clause of a query
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Q, or in outer queries that contain Q.
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NOTES
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The name resolution algorithm used is (where [T_j] is an optional table
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name that qualifies the column name):
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resolve_column_reference([T_j].col_ref_i)
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{
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search for a column or derived column named col_ref_i
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[in table T_j] in the FROM clause of Q;
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if such a column is NOT found AND // Lookup in outer queries.
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there are outer queries
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{
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for each outer query Q_k beginning from the inner-most one
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{
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if - Q_k is not a group query AND
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- Q_k is not inside an aggregate function
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OR
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- Q_(k-1) is not in a HAVING or SELECT clause of Q_k
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{
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search for a column or derived column named col_ref_i
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[in table T_j] in the FROM clause of Q_k;
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}
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if such a column is not found
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Search for a column or derived column named col_ref_i
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[in table T_j] in the SELECT and GROUP clauses of Q_k.
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}
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}
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}
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Notice that compared to Item_ref::fix_fields, here we first search the FROM
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clause, and then we search the SELECT and GROUP BY clauses.
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RETURN
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TRUE if error
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FALSE on success
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*/
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bool Item_field::fix_fields(THD *thd, TABLE_LIST *tables, Item **reference)
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{
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DBUG_ASSERT(fixed == 0);
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@ -1672,10 +1725,6 @@ bool Item_field::fix_fields(THD *thd, TABLE_LIST *tables, Item **reference)
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if (ref != not_found_item)
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{
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DBUG_ASSERT(*ref && (*ref)->fixed);
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/*
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Avoid crash in case of error.
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TODO: what does this comment mean?
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*/
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prev_subselect_item->used_tables_cache|= (*ref)->used_tables();
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prev_subselect_item->const_item_cache&= (*ref)->const_item();
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break;
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@ -1699,7 +1748,7 @@ bool Item_field::fix_fields(THD *thd, TABLE_LIST *tables, Item **reference)
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{
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if (upward_lookup)
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{
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// We can't say exactly what absend table or field
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// We can't say exactly what absent table or field
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my_printf_error(ER_BAD_FIELD_ERROR, ER(ER_BAD_FIELD_ERROR), MYF(0),
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full_name(), thd->where);
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}
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@ -2460,12 +2509,12 @@ bool Item_field::send(Protocol *protocol, String *buffer)
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/*
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Resolve the name of a column reference.
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Resolve the name of a reference to a column reference.
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SYNOPSIS
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Item_ref::fix_fields()
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thd [in] current thread
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tables [in] the tables in the FROM clause
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tables [in] the tables in a FROM clause
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reference [in/out] view column if this item was resolved to a view column
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DESCRIPTION
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@ -2475,7 +2524,8 @@ bool Item_field::send(Protocol *protocol, String *buffer)
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aggregate functions.
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NOTES
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The name resolution algorithm used is:
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The name resolution algorithm used is (where [T_j] is an optional table
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name that qualifies the column name):
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resolve_extended([T_j].col_ref_i)
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{
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@ -2504,7 +2554,9 @@ bool Item_field::send(Protocol *protocol, String *buffer)
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}
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This procedure treats GROUP BY and SELECT clauses as one namespace for
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column references in HAVING.
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column references in HAVING. Notice that compared to
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Item_field::fix_fields, here we first search the SELECT and GROUP BY
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clauses, and then we search the FROM clause.
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RETURN
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TRUE if error
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@ -2559,10 +2611,6 @@ bool Item_ref::fix_fields(THD *thd, TABLE_LIST *tables, Item **reference)
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if (ref != not_found_item)
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{
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DBUG_ASSERT(*ref && (*ref)->fixed);
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/*
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Avoid crash in case of error.
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TODO: what does this comment mean?
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*/
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prev_subselect_item->used_tables_cache|= (*ref)->used_tables();
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prev_subselect_item->const_item_cache&= (*ref)->const_item();
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break;
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@ -2675,13 +2723,9 @@ bool Item_ref::fix_fields(THD *thd, TABLE_LIST *tables, Item **reference)
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}
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/*
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The following conditional is changed as to correctly identify
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incorrect references in group functions or forward references
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with sub-select's / derived tables, while it prevents this
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check when Item_ref is created in an expression involving
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summing function, which is to be placed in the user variable.
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TODO: this comment is impossible to understand.
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Check if this is an incorrect reference in a group function or forward
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reference. Do not issue an error if this is an unnamed reference inside an
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aggregate function.
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*/
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if (((*ref)->with_sum_func && name &&
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(depended_from ||
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