MySQL 8.0.29
Source Code Documentation
replace_item.h
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22
23#ifndef SQL_JOIN_OPTIMIZER_REPLACE_ITEM_H
24#define SQL_JOIN_OPTIMIZER_REPLACE_ITEM_H
25
26class Func_ptr;
27class Item;
28class Item_field;
29template <class T>
30class Mem_root_array;
31class THD;
33
34/*
35 Return a new item that is to be used after materialization (as given by
36 items_to_copy). There are three main cases:
37
38 1. The item isn't touched by materialization (e.g., because it's constant,
39 or because we're not ready to compute it yet).
40 2. The item is directly in the items_to_copy list, so it has its own field
41 in the resulting temporary table; the corresponding new Item_field
42 is returned.
43 3. A _part_ of the item is in the items_to_copy list; e.g. say that we
44 have an item (t1.x + 1), and t1.x is materialized into <temporary>.x.
45 (In particular, this happens when having expressions that contain
46 aggregate functions _and_ non-aggregates.) In this case, we go in and
47 modify the item in-place, so that the appropriate sub-expressions are
48 replaced; in this case, to (<temporary>.x + 1). This assumes that we
49 never use the same item before and after a materialization in the
50 query plan!
51 */
53 THD *thd, Item *item, const Func_ptr_array &items_to_copy,
54 bool need_exact_match);
55
56/**
57 Like FindReplacementOrReplaceMaterializedItems, but only search _below_ the
58 item, ie. ignore point 2 above. This can be useful if doing self-replacement,
59 ie., we are replacing source items in items_to_copy and don't want to
60 replace an item with its own output.
61 */
62void ReplaceMaterializedItems(THD *thd, Item *item,
63 const Func_ptr_array &items_to_copy,
64 bool need_exact_match);
65
66#endif // SQL_JOIN_OPTIMIZER_REPLACE_ITEM_H
Helper class for copy_funcs(); represents an Item to copy from table to next tmp table.
Definition: temp_table_param.h:51
Definition: item.h:4043
Base class that is used to represent any kind of expression in a relational query.
Definition: item.h:802
A typesafe replacement for DYNAMIC_ARRAY.
Definition: mem_root_array.h:421
For each client connection we create a separate thread with THD serving as a thread/connection descri...
Definition: sql_class.h:945
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.
Definition: replace_item.cc:101
Item * FindReplacementOrReplaceMaterializedItems(THD *thd, Item *item, const Func_ptr_array &items_to_copy, bool need_exact_match)
Definition: replace_item.cc:81