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

Functions
static Item *	possibly_outerize_replacement (Item sub_item, Item replacement)

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, Func_ptr_array *agg_items_to_copy)

void	ReplaceMaterializedItems (THD thd, Item item, const Func_ptr_array &items_to_copy, bool need_exact_match, bool window_frame_buffer)
	Like FindReplacementOrReplaceMaterializedItems, but only search below the item, ie. More...

Item *	ReplaceSetVarItem (THD thd, Item item, Item *new_item)
	Replace "@var:=<expr>" with "@var:=<tmp_table_column>" rather than "<tmp_table_column>". 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,
		Func_ptr_array *	agg_items_to_copy
	)

◆ possibly_outerize_replacement()

static Item * possibly_outerize_replacement	(	Item *	sub_item,
		Item *	replacement
	)

static

◆ ReplaceMaterializedItems()

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

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.

◆ ReplaceSetVarItem()

Item * ReplaceSetVarItem	(	THD *	thd,
		Item *	item,
		Item *	new_item
	)

Replace "@var:=<expr>" with "@var:=<tmp_table_column>" rather than "<tmp_table_column>".

If a join field such as "@var:=expr" points to a temp table field, the var assignment won't happen because there is no re-evaluation of the materialized field. . So, rather than returning the temp table field, return a new Item_func_set_user_var item that points to temp table field, so that "@var" gets updated.

(It's another thing that the temp table field itself is an Item_func_set_user_var field, i.e. of the form "@var:=<expr>", which means the var assignment redundantly happens for each temp table record while initializing the table; but this function does not fix that)