replace_item.cc File Reference

#include "sql/join_optimizer/replace_item.h"
#include "sql/item.h"
#include "sql/sql_resolver.h"
#include "sql/temp_table_param.h"

Functions
static Item *	FindReplacementItem (Item *item, const Func_ptr_array &items_to_copy, bool need_exact_match)
	Check what field the given item will be materialized into under the given temporary table parameters. More...
Item *	FindReplacementOrReplaceMaterializedItems (THD *thd, Item *item, const Func_ptr_array &items_to_copy, bool need_exact_match)
void	ReplaceMaterializedItems (THD *thd, Item *item, const Func_ptr_array &items_to_copy, bool need_exact_match)
	Like FindReplacementOrReplaceMaterializedItems, but only search below the item, ie. More...

Function Documentation

FindReplacementItem()

static Item * FindReplacementItem ( Item *  item, const Func_ptr_array &  items_to_copy, bool  need_exact_match  )

static

Check what field the given item will be materialized into under the given temporary table parameters.

If the item is materialized (ie., found in items_to_copy), we return a canonical Item_field for that field; ie., the same every time. This means that you can do the same replacement in a SELECT list and then in items_to_copy itself, and still have them match. This is used in particular when updating Temp_table_param itself, in FinalizePlanForQueryBlock().

Normally, we want to search for only the same item, up to references (need_exact_match=true). However, in ORDER BY specifications of windows, we can sometimes have the same field referred to by different Item_field, and the callers may need to set need_exact_match=false, which compares using Item::eq() instead. This also disables the behavior of checking and propagating Item::hidden.

FindReplacementOrReplaceMaterializedItems()

Item * FindReplacementOrReplaceMaterializedItems	(	THD *	thd,
		Item *	item,
		const Func_ptr_array &	items_to_copy,
		bool	need_exact_match
	)

ReplaceMaterializedItems()

void ReplaceMaterializedItems	(	THD *	thd,
		Item *	item,
		const Func_ptr_array &	items_to_copy,
		bool	need_exact_match
	)

Like FindReplacementOrReplaceMaterializedItems, but only search below the item, ie.

ignore point 2 above. This can be useful if doing self-replacement, ie., we are replacing source items in items_to_copy and don't want to replace an item with its own output.