/**

* Copyright (c) 2021 OceanBase

* OceanBase CE is licensed under Mulan PubL v2.

* You can use this software according to the terms and conditions of the Mulan PubL v2.

* You may obtain a copy of Mulan PubL v2 at:

* http://license.coscl.org.cn/MulanPubL-2.0

* THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND,

* EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT,

* MERCHANTABILITY OR FIT FOR A PARTICULAR PURPOSE.

* See the Mulan PubL v2 for more details.

*/

#ifndef OB_TRANSFORM_EXPR_PULLUP_H

#define OB_TRANSFORM_EXPR_PULLUP_H

#include "sql/rewrite/ob_transform_rule.h"

namespace oceanbase {

namespace sql {

class ObExprNodeMap

{

public:

struct ExprCounter {

ExprCounter() : expr_(nullptr), count_(0) {}

ObRawExpr *expr_;

int64_t count_;

};

ObExprNodeMap() {}

int init();

int add_expr_map(ObRawExpr *expr);

int is_exist(ObRawExpr *expr, bool &is_exist);

int get_ref_count(ObRawExpr *expr, int64_t &ref_count);

private:

uint64_t get_hash_value(ObRawExpr *expr) {

return (uint64_t)(expr);

}

private:

hash::ObHashMap<uint64_t, ExprCounter, hash::NoPthreadDefendMode> expr_map_;

};

class ObTransformExprPullup : public ObTransformRule

{

public:

ObTransformExprPullup(ObTransformerCtx *ctx)

: ObTransformRule(ctx, TransMethod::POST_ORDER, T_PULLUP_EXPR)

{}

virtual ~ObTransformExprPullup() {}

virtual int transform_one_stmt(common::ObIArray<ObParentDMLStmt> &parent_stmts,

ObDMLStmt *&stmt,

bool &trans_happened) override;

virtual int transform_one_stmt_with_outline(common::ObIArray<ObParentDMLStmt> &parent_stmts,

ObDMLStmt *&stmt,

bool &trans_happened) override;

virtual int need_transform(const common::ObIArray<ObParentDMLStmt> &parent_stmts,

const int64_t current_level,

const ObDMLStmt &stmt, bool &need_trans) override;

virtual int construct_transform_hint(ObDMLStmt &stmt, void *trans_params) override;

protected:

private:

int build_parent_reject_exprs_map(ObSelectStmt &parent,

ObExprNodeMap &expr_reject_map,

ObExprNodeMap &subquery_reject_map);

int check_stmt_validity(const ObDMLStmt *stmt, bool &is_valid);

int rewrite_decision_by_hint(ObSelectStmt &parent, ObSelectStmt &ref_query,

bool stmt_may_reduce_row_count, bool &go_rewrite);

int transform_view_recursively(TableItem *table_item, ObSelectStmt &stmt,

ObExprNodeMap &parent_reject_expr_map,

ObExprNodeMap &parent_reject_subquery_map,

common::ObIArray<ObSelectStmt *> &transformed_views,

bool stmt_may_reduce_row_count, bool &trans_happened);

int pullup_expr_from_view(TableItem *view, ObSelectStmt &select_stmt,

ObExprNodeMap &parent_reject_expr_map,

ObExprNodeMap &parent_reject_subquery_map,

common::ObIArray<ObSelectStmt *> &transformed_stmts,

bool stmt_may_reduce_row_count, bool &trans_happened);

int extract_params(ObRawExpr *expr, ObExprNodeMap &child_reject_map,

common::ObIArray<ObRawExpr*> &param_exprs);

int search_expr_cannot_pullup(ObRawExpr *expr,

ObExprNodeMap &expr_map,

common::ObIArray<ObRawExpr *> &expr_cannot_pullup);

int adjust_subquery(ObRawExpr *expr, ObSelectStmt &child, ObSelectStmt &parent);

int is_stmt_may_reduce_row_count(const ObSelectStmt &stmt, bool &is_true);

static bool is_view_acceptable_for_rewrite(TableItem &view);

static bool expr_can_pullup(ObRawExpr *expr);

static bool expr_need_pullup(ObRawExpr *expr);

};

}

}

#endif // OB_TRANSFORM_EXPR_PULLUP_H