232 lines
10 KiB
C++
232 lines
10 KiB
C++
/**
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* Copyright (c) 2021 OceanBase
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* OceanBase CE is licensed under Mulan PubL v2.
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* You can use this software according to the terms and conditions of the Mulan PubL v2.
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* You may obtain a copy of Mulan PubL v2 at:
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* http://license.coscl.org.cn/MulanPubL-2.0
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* THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND,
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* EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT,
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* MERCHANTABILITY OR FIT FOR A PARTICULAR PURPOSE.
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* See the Mulan PubL v2 for more details.
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*/
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#ifndef OB_TRANSFORM_SIMPILFY_SUBQUERY_H
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#define OB_TRANSFORM_SIMPILFY_SUBQUERY_H
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#include "sql/rewrite/ob_transform_rule.h"
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#include "sql/rewrite/ob_transform_utils.h"
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namespace oceanbase {
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namespace sql {
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class ObTransformSimplifySubquery : public ObTransformRule
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{
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public:
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ObTransformSimplifySubquery(ObTransformerCtx *ctx)
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: ObTransformRule(ctx, TransMethod::POST_ORDER, T_SIMPLIFY_SUBQUERY)
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{}
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virtual ~ObTransformSimplifySubquery() {}
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virtual int transform_one_stmt(common::ObIArray<ObParentDMLStmt> &parent_stmts,
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ObDMLStmt *&stmt,
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bool &trans_happened) override;
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private:
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int transform_subquery_as_expr(ObDMLStmt *stmt, bool &trans_happened);
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int try_trans_subquery_in_expr(ObDMLStmt *stmt,
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ObRawExpr *&expr,
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bool &trans_happened);
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int do_trans_subquery_as_expr(ObDMLStmt *stmt,
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ObRawExpr *&expr,
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bool &trans_happened);
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int is_subquery_to_expr_valid(const ObSelectStmt *stmt,
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bool &is_valid);
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int transform_not_expr(ObDMLStmt *stmt, bool &trans_happened);
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int do_transform_not_expr(ObRawExpr *&expr, bool &trans_happened);
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int remove_redundant_select(ObDMLStmt *&stmt, bool &trans_happened);
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int try_remove_redundant_select(ObSelectStmt &stmt, ObSelectStmt *&new_stmt);
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int check_subquery_valid(ObSelectStmt &stmt, bool &is_valid);
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int push_down_outer_join_condition(ObDMLStmt *stmt, bool &trans_happened);
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int push_down_outer_join_condition(ObDMLStmt *stmt,
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TableItem *join_table,
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bool &trans_happened);
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int try_push_down_outer_join_conds(ObDMLStmt *stmt,
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JoinedTable *join_table,
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bool &trans_happened);
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ObItemType get_opposite_expr_type(ObItemType item_type);
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int add_limit_for_exists_subquery(ObDMLStmt *stmt,bool &trans_happened);
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int recursive_add_limit_for_exists_expr(ObRawExpr *expr, bool &trans_happened);
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/**
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* @brief transform_any_all
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* 遍历stmt中不同部分中的表达式，并尝试对其改写
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*/
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int transform_any_all(ObDMLStmt *stmt, bool &trans_happened);
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/**
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* @brief try_trans_any_all
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* 尝试对表达式 expr 本身或者它的参数表达式进行改写
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*/
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int try_transform_any_all(ObDMLStmt *stmt, ObRawExpr *&expr, bool &trans_happened);
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/**
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* @brief do_trans_any_all
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* 判断一个表达式是否可以进行改写，如果可以那么进行改写
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*/
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int do_transform_any_all(ObDMLStmt *stmt, ObRawExpr *&expr, bool &trans_happened);
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int check_any_all_as_min_max(ObRawExpr *expr, bool &is_valid);
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int transform_any_all_as_min_max(ObDMLStmt *stmt, ObRawExpr *expr, bool &trans_happened);
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int do_transform_any_all_as_min_max(ObSelectStmt *sel_stmt, const ObItemType aggr_type,
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bool is_with_all, bool &trans_happened);
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/**
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* @brief ObTransformAnyAll::eliminate_any_all_for_scalar_query
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* 如果 subquery 返回的记录数量为0或者1，那么 any 可以消除
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* 如果 subquery 返回记录数量为1，那么 all 可以消除
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* rel.c > all 空集 与 rel.c > 空集 语义不相同
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*/
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int eliminate_any_all_before_subquery(ObDMLStmt *stmt, ObRawExpr *&expr, bool &trans_happened);
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/**
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* @brief is_any_all_removeable
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* 判断一个subquery compare 表达式的 any/all flag是否可以移除
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*/
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int check_any_all_removeable(ObRawExpr *expr, bool &can_be_removed);
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/**
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* @brief clear_any_all_flag
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* 将一个 subquery compare 表达式 expr 替换为相应的 common compare 表达式
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*/
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int clear_any_all_flag(ObDMLStmt *stmt, ObRawExpr *&expr, ObQueryRefRawExpr *query_ref);
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ObItemType get_aggr_type(ObItemType op_type, bool is_with_all);
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ObItemType query_cmp_to_value_cmp(const ObItemType cmp_type);
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int transform_exists_query(ObDMLStmt *stmt, bool &trans_happened);
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int try_eliminate_subquery(ObDMLStmt *stmt, ObRawExpr *&expr, bool &trans_happened);
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/**
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* Simplify subuqery in exists, any, all (subq)
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* 1. Eliminate subquery if possible
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* 2. Eliminate select list to const 1
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* 3. Eliminate group by
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*/
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int recursive_eliminate_subquery(ObDMLStmt *stmt, ObRawExpr *&expr,
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bool &trans_happened);
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int eliminate_subquery(ObDMLStmt *stmt,
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ObRawExpr *&expr,
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bool &trans_happened);
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/**
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* 当[not] exists(subq)满足以下所有条件时，subquery可以被消除
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* 1. 当前stmt不是set stmt
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* 2. 当前stmt不包含having或group by
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* 3. stmt包含聚集函数
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*/
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static bool is_subquery_not_empty(const ObSelectStmt &stmt);
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int subquery_can_be_eliminated_in_exists(const ObItemType op_type,
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const ObSelectStmt *stmt,
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bool &can_be_eliminated) const;
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/**
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* 当[not] exists(subq)满足以下所有条件时，select list可替换为1
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* 1. 当前stmt不是set stmt
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* 2. distinct和limit不同时存在
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*/
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int select_items_can_be_simplified(const ObItemType op_type,
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const ObSelectStmt *stmt,
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bool &can_be_simplified) const;
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/**
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* 当[not] exists(subq)满足以下所有条件时，可消除group by子句:
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* 1. 当前stmt不是set stmt
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* 2. 没有having子句
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* 3. 没有limit子句
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*/
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int groupby_can_be_eliminated_in_exists(const ObItemType op_type,
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const ObSelectStmt *stmt,
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bool &can_be_eliminated) const;
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/**
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* 当Any/all/in(subq)满足以下所有条件时，可消除group by子句:
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* 1. 当前stmt不是set stmt
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* 2. 没有having子句
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* 3. 没有limit子句
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* 4. 无聚集函数（select item中）
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* 5. 非常量select item列，全部包含在group exprs中
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*/
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int groupby_can_be_eliminated_in_any_all(const ObSelectStmt *stmt, bool &can_be_eliminated) const;
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int eliminate_subquery_in_exists(ObDMLStmt *stmt,
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ObRawExpr *&expr,
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bool &trans_happened);
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int simplify_select_items(ObDMLStmt *stmt,
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const ObItemType op_type,
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ObSelectStmt *subquery,
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bool parent_is_set_query,
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bool &trans_happened);
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int eliminate_groupby_in_exists(ObDMLStmt *stmt,
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const ObItemType op_type,
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ObSelectStmt *&subquery,
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bool &trans_happened);
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int eliminate_groupby_distinct_in_any_all(ObRawExpr *expr, bool &trans_happened);
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int eliminate_groupby_in_any_all(ObSelectStmt *&stmt, bool &trans_happened);
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int eliminate_distinct_in_any_all(ObSelectStmt *subquery,bool &trans_happened);
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int check_need_add_limit(ObSelectStmt *subquery, bool &need_add_limit);
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int check_limit(const ObItemType op_type,
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const ObSelectStmt *subquery,
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bool &has_limit) const;
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int need_add_limit_constraint(const ObItemType op_type,
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const ObSelectStmt *subquery,
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bool &add_limit_constraint) const;
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int check_const_select(const ObSelectStmt &stmt, bool &is_const_select) const;
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int get_push_down_conditions(ObDMLStmt *stmt,
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JoinedTable *join_table,
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ObIArray<ObRawExpr *> &join_conds,
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ObIArray<ObRawExpr *> &push_down_conds);
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int try_trans_any_all_as_exists(ObDMLStmt *stmt,
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ObRawExpr *&expr,
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ObNotNullContext *not_null_ctx,
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bool is_bool_expr,
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bool &trans_happened);
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int do_trans_any_all_as_exists(ObRawExpr *&expr,
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ObNotNullContext *not_null_ctx,
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bool &trans_happened);
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int check_can_trans_as_exists(ObRawExpr* expr, bool is_bool_expr, bool &is_valid);
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int check_stmt_can_trans_as_exists(ObSelectStmt *stmt,
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bool is_correlated,
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bool &match_index,
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bool &is_valid);
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int query_cmp_to_exists_value_cmp(ObItemType type, bool is_with_all, ObItemType& new_type);
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int add_limit_for_any_all_subquery(ObRawExpr *stmt,bool &trans_happened);
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int prepare_trans_any_all_as_exists(ObQueryRefRawExpr* expr, ObSelectStmt *&trans_stmt);
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int transform_any_all_as_exists(ObDMLStmt *stmt, bool &trans_happened);
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int transform_any_all_as_exists_joined_table(ObDMLStmt* stmt,
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TableItem *table,
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bool &trans_happened);
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int try_trans_any_all_as_exists(ObDMLStmt *stmt,
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ObIArray<ObRawExpr* > &exprs,
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ObNotNullContext *not_null_cxt,
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bool is_bool_expr,
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bool &trans_happened);
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int empty_table_subquery_can_be_eliminated_in_exists(ObRawExpr *expr,
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bool &is_valid);
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int do_trans_empty_table_subquery_as_expr(ObRawExpr *&expr,
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bool &trans_happened);
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};
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}
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}
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#endif // OB_TRANSFORM_SIMPILFY_SUBQUERY_H
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