254 lines
10 KiB
C++
254 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_WHERE_SUBQUERY_PULLUP_H_
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#define _OB_WHERE_SUBQUERY_PULLUP_H_
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#include "sql/rewrite/ob_transform_rule.h"
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#include "sql/resolver/dml/ob_select_stmt.h"
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namespace oceanbase
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{
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namespace sql
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{
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/**
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* 这个类主要进行和子查询相关的SQL改写，它主要分为两类：
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* 1. eliminate_subquery 简化子查询的某一部分，或者移除整个冗余的子查询
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* （1）移除整个冗余的子查询
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* 1. 对于在执行前即可计算出恒TURE或者恒FALSE的EXIST / NOT EXIST
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* 语句，可以在这一阶段消除，替换成相应的TURE或者FALSE，判断规则见
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* subquery_can_be_eliminated_in_exists()
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* （2）简化子查询的一部分
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* 1. 对于不能消除的EXIST / NOT EXIST，它的SELECT LIST和ORDER BY均可
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* 消除；在一定条件下，GROUP BY也可以消除，判断规则见
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* groupby_can_be_eliminated_in_exists()
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* 2. 对于不能消除的EXIST / NOT EXIST，如果本身没有LIMIT语句，会为它加
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* 上LIMIT 1。
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* 3. 对于ANY / ALL子查询，在一定条件下，GROUP BY也可以消除，判断规则见
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* groupby_can_be_eliminated_in_any_all()
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*
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* 2. pullup_subquery 将子查询提升为一个view或者合并到主查询中
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* （1）将子查询合并到主查询中，改写成SEMI JOIN或者ANTI JOIN
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* 通常认为改写（2）要优于改写（3），如果能直接合并入主查询中，不会再进行改写（3）
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* e.g.
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* （示例1：子查询和主查询相关联）
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* SELECT * FROM T1 WHERE T1.c1 in (SELECT T2.c1 FROM T2 WHERE T1.c2 < T2.c2)
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* ->
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* SELECT *
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* FROM T1 SEMI JOIN T2
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* WHERE T1.c1 = T2.c1 AND T1.c2 < T2.c2
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* （2）将和主查询无关的子查询提升为一个view，改写成SEMI JOIN或者ANTI JOIN
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* e.g.
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* SELECT * FROM T1 WHERE T1.c1 in (SELECT T2.c1 FROM T2 LIMIT 3)
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* ->
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* SELECT *
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* FROM T1 SEMI JOIN (SELECT T2.c1 FROM T2 LIMIT 3) AS SUBQ
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* WHERE T1.c1 = SUBQ.c1
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*
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*/
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class ObWhereSubQueryPullup : public ObTransformRule
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{
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public:
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ObWhereSubQueryPullup(ObTransformerCtx *ctx)
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: ObTransformRule(ctx, TransMethod::POST_ORDER, T_UNNEST)
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{}
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virtual ~ObWhereSubQueryPullup() {}
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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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virtual int transform_one_stmt_with_outline(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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struct SingleSetParam {
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SingleSetParam():
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query_ref_expr_(NULL),
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not_null_column_(NULL),
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null_reject_select_idx_(),
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use_outer_join_(false)
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{}
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virtual ~SingleSetParam(){}
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TO_STRING_KV(
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K_(query_ref_expr),
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K_(not_null_column),
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K_(null_reject_select_idx),
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K_(use_outer_join)
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);
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ObQueryRefRawExpr *query_ref_expr_;
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ObRawExpr *not_null_column_;
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ObSqlBitSet<> null_reject_select_idx_;
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bool use_outer_join_;
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};
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struct TransformParam {
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TransformParam() : op_(NULL),
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subquery_expr_(NULL),
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subquery_(NULL),
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left_hand_(NULL),
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can_be_transform_(true),
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is_correlated_(false),
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need_create_spj_(false),
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need_add_limit_constraint_(false)
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{}
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ObOpRawExpr *op_; // the all/any/exists contain subquery expr;
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ObQueryRefRawExpr *subquery_expr_;//the query expr
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ObSelectStmt *subquery_; //subquery select stmt
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ObRawExpr *left_hand_; //the all/any op left expr
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bool can_be_transform_; //能否被改写
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bool is_correlated_;//是否直接相关的
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bool need_create_spj_;
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//Just in case different parameters hit same plan, firstly we need add const param constraint
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bool need_add_limit_constraint_;
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TO_STRING_KV(K_(op),
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K_(subquery_expr),
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K_(subquery),
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K_(left_hand),
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K_(can_be_transform),
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K_(is_correlated),
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K_(need_create_spj),
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K_(need_add_limit_constraint));
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};
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int transform_anyall_query(ObDMLStmt *stmt,
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ObIArray<ObSelectStmt*> &unnest_stmts,
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bool &trans_happened);
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int transform_single_set_query(ObDMLStmt *stmt,
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ObIArray<ObSelectStmt*> &unnest_stmts,
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bool &trans_happened);
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int transform_one_expr(ObDMLStmt *stmt,
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ObRawExpr *expr,
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ObIArray<ObSelectStmt*> &unnest_stmts,
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bool &trans_happened);
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int gather_transform_params(ObDMLStmt *stmt,
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ObRawExpr *expr,
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TransformParam &trans_param);
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int can_be_unnested(const ObItemType op_type,
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const ObSelectStmt *subquery,
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bool &can_be,
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bool &need_add_limit_constraint);
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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,
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bool &need_add_limit_constraint) const;
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int do_transform_pullup_subquery(ObDMLStmt* stmt, ObRawExpr* expr, TransformParam &trans_param, bool &trans_happened);
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int get_single_set_subquery(ObDMLStmt &stmt,
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ObRawExpr *root_expr,
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ObRawExpr *expr,
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bool in_where_cond,
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ObIArray<SingleSetParam> &queries);
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int check_subquery_validity(ObDMLStmt &stmt,
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ObRawExpr *root_expr,
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ObQueryRefRawExpr *subquery_expr,
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bool in_where_cond,
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ObIArray<SingleSetParam> &queries);
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bool is_vector_query(ObQueryRefRawExpr *query);
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int unnest_single_set_subquery(ObDMLStmt *stmt,
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SingleSetParam& param,
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const bool is_vector_assign);
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int wrap_case_when_for_select_expr(SingleSetParam& param,
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ObIArray<ObRawExpr *> &select_exprs);
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int wrap_case_when(ObSelectStmt &child_stmt,
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ObRawExpr *not_null_column,
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ObRawExpr *&expr);
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int pull_up_semi_info(ObDMLStmt* stmt,
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ObSelectStmt* subquery);
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int trans_from_list(ObDMLStmt *stmt,
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ObSelectStmt *subquery,
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const bool use_outer_join);
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int pullup_non_correlated_subquery_as_view(ObDMLStmt *stmt,
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ObSelectStmt *subquery,
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ObRawExpr *expr,
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ObQueryRefRawExpr *subquery_expr);
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int pullup_correlated_subquery_as_view(ObDMLStmt *stmt,
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ObSelectStmt *subquery,
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ObRawExpr *expr,
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ObQueryRefRawExpr *subquery_expr);
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int check_transform_validity(ObDMLStmt *stmt, const ObRawExpr* expr, TransformParam &trans_param);
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int check_basic_validity(ObDMLStmt *stmt, const ObRawExpr* expr, TransformParam &trans_param);
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int check_subquery_validity(ObQueryRefRawExpr *query_ref,
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ObSelectStmt *subquery,
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bool is_correlated,
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bool &is_valid);
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int pull_up_tables_and_columns(ObDMLStmt* stmt, ObSelectStmt* subquery);
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int generate_conditions(ObDMLStmt *stmt,
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ObIArray<ObRawExpr *> &subq_exprs,
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ObSelectStmt* subquery,
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ObRawExpr *expr,
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ObIArray<ObRawExpr*> &semi_conds,
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ObIArray<ObRawExpr*> &right_conds);
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int get_semi_oper_type(ObRawExpr *op, ObItemType &oper_type);
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int generate_anti_condition(ObDMLStmt *stmt,
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const ObSelectStmt *subquery,
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ObRawExpr* expr,
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ObRawExpr* left_arg,
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ObRawExpr* right_arg,
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ObRawExpr* generated_column_,
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ObRawExpr* &anti_expr);
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int make_null_test(ObDMLStmt *stmt, ObRawExpr *in_expr, ObRawExpr *&out_expr);
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int generate_semi_info(ObDMLStmt* stmt,
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ObRawExpr* expr,
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TableItem *right_table,
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ObIArray<ObRawExpr*> &semi_conditions,
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SemiInfo *&semi_info);
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int fill_semi_left_table_ids(ObDMLStmt *stmt,
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SemiInfo *info);
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int is_where_having_subquery_correlated(const ObIArray<ObExecParamRawExpr *> &exec_params,
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const ObSelectStmt &subquery,
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bool &is_correlated);
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int check_const_select(const ObSelectStmt &stmt, bool &is_const_select) const;
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virtual int check_hint_status(const ObDMLStmt &stmt, bool &need_trans) override;
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virtual int construct_transform_hint(ObDMLStmt &stmt, void *trans_params) override;
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int check_hint_allowed_unnest(const ObDMLStmt &stmt,
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const ObSelectStmt &subquery,
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bool &allowed);
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private:
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DISALLOW_COPY_AND_ASSIGN(ObWhereSubQueryPullup);
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};
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}
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}
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#endif /* _OB_WHERE_SUBQUERY_PULLUP_H_ */
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