diff options
| -rw-r--r-- | BitKeeper/etc/logging_ok | 1 | ||||
| -rw-r--r-- | Docs/internals.texi | 17 |
2 files changed, 14 insertions, 4 deletions
diff --git a/BitKeeper/etc/logging_ok b/BitKeeper/etc/logging_ok index b00af7095d7..085c67a176c 100644 --- a/BitKeeper/etc/logging_ok +++ b/BitKeeper/etc/logging_ok @@ -13,6 +13,7 @@ arjen@george.bitbike.com bar@bar.mysql.r18.ru bar@bar.udmsearch.izhnet.ru bar@gw.udmsearch.izhnet.ru +bell@laptop.sanja.is.com.ua bell@sanja.is.com.ua bk@admin.bk davida@isil.mysql.com diff --git a/Docs/internals.texi b/Docs/internals.texi index c8cf335e2f4..9f9b08b96c3 100644 --- a/Docs/internals.texi +++ b/Docs/internals.texi @@ -649,7 +649,7 @@ Item_in_subselect inherit mechanism of getting value from Item_exists_subselect. @item Select_transformer stores reference to left expression in its - conditions: (in WHERE in case 'a' and in a HAVING in case 'b') + conditions: (in WHERE & HAVING in case 'a' and in a HAVING in case 'b') @item Item from item list of this select (t2.a) can be referred with special reference (Item_ref_null_helper or Item_asterisk_remover). @@ -704,6 +704,13 @@ ORDER BY without LIMIT here. If IN subselect union condition of every select in UNION will be changed personally. +If condition should be added to WHERE clause it will be presented as +"(item OR item IS NULL)" and Item_is_not_null_test(item) will be added +to HAVING clause. Item_is_not_null_test register NULL value as +Item_ref_null_helper does it and return FALSE if argument is NULL. +With above trick we will register NULL value of Item even in case +of index optimization of WHERE clause (case 'a' of following example). + Following is examples of IN transformations: @example a) <left_expression> IN (SELECT <item> FROM t @@ -712,8 +719,11 @@ a) <left_expression> IN (SELECT <item> FROM t will be represented as (SELECT 1 FROM t - WHERE <where_exp> and - Item_ref(<cached_left_expression>)=<Item_asterisk_remover(<Item>)>) + WHERE + <where_exp> and + (Item_ref(<cached_left_expression>)=<Item_asterisk_remover(<Item>)> or + <Item> is null) + HAVING Item_is_not_null_test(<Item>)) b) <left_expression> IN (SELECT <item> FROM t @@ -721,7 +731,6 @@ b) <left_expression> IN (SELECT <item> FROM t ORDER BY 1) will be represented as - (SELECT <item> as ref_null_helper FROM t HAVING <having_exp> AND Item_ref(<cached_left_expression>) = ref_null_helper) |