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: fix swcb qual push down issues 

Offering: openGaussDev

More detail: push down only join quals and leave filter quals outside of the sw op

Match-id-85219d101564ac6e5b2a3b575e9738c3ba1ccdca
This commit is contained in:
openGaussDev 2022-03-08 17:01:08 +08:00 committed by yanghao
parent 8b5d92a0e2
commit 2b09dd1a67
4 changed files with 93 additions and 8 deletions
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63
src/common/backend/parser/parse_startwith.cpp
View File

@ -1105,12 +1105,24 @@ static void transformStartWithClause(StartWithTransformContext *context, SelectS
StartWithWalker(context, connectByExpr);
}
/* now handle where quals which could whole push down */
/*
* now handle where quals which might need to be pushed down.
* 1. this is necessary only for implicitly joined tables
* such as ... FROM t1,t2 WHERE t1.xx = t2.yy ...
* 2. note that only join quals should be pushed down while
* non-join quals such as (t1.xx < n) should be kept in the outer loop
* of the CTE scan, otherwise the end-result will be different from
* those produced by the standard swcb syntax.
* (the issue here is that implicitly joined tables are difficult to handle
* in our implementation of start with .. connect by .. syntax,
* as we don't have a clear cut of join quals from the non-join quals at this stage.
* users should be encouraged to use explicity joined tables whenever
* possible before a clear-cut solution is implemented.)
*/
int lens = list_length(context->pstate->p_start_info);
if (lens != 1) {
Node *whereClause = (Node *)copyObject(stmt->whereClause);
context->whereClause = whereClause;
stmt->whereClause = NULL;
}
@ -1258,6 +1270,36 @@ static void AddWithClauseToBranch(ParseState *pstate, SelectStmt *stmt, List *re
return;
}
static bool walker_to_exclude_non_join_quals(Node *node, Node *context_node)
{
if (node == NULL) {
return false;
}
if (!IsA(node, A_Expr)) {
return raw_expression_tree_walker(node, (bool (*)()) walker_to_exclude_non_join_quals, (void*)NULL);
}
A_Expr* expr = (A_Expr*) node;
/*
* this is to achieve consistent result sets with those produced by the original
* start with .. connect by syntax, which does not push filter quals down to connect quals.
* if non-column item appears on any side of an operator, we guess that it is
* not a join qual so should not be filtered in sw op, and force it to be true.
* this rule is not always correct but should work fine most of the time.
* could be improved later on, e.g. find better ways to extract non-join quals
* from the where clause.
*/
if (expr->kind == AEXPR_OP &&
(!IsA(expr->lexpr, ColumnRef) || !IsA(expr->rexpr, ColumnRef))) {
expr->lexpr = makeBoolAConst(true, -1);
expr->rexpr = makeBoolAConst(true, -1);
expr->kind = AEXPR_OR;
}
return false;
}
/*
* --------------------------------------------------------------------------------------
* @Brief: Create SWCB's conversion CTE's inner branch, normally we add ConnectByExpr to
@ -1316,6 +1358,10 @@ static SelectStmt *CreateStartWithCTEInnerBranch(ParseState* pstate,
JoinExpr *final_join = (JoinExpr *)origin_table;
/* pushdown requires deep copying of the quals */
Node *whereCopy = (Node *)copyObject(whereClause);
/* only join quals can be pushed down */
raw_expression_tree_walker((Node *)whereCopy,
(bool (*)())walker_to_exclude_non_join_quals, (void*)NULL);
if (final_join->quals == NULL) {
final_join->quals = whereCopy;
} else {
@ -1422,11 +1468,18 @@ static SelectStmt *CreateStartWithCTEOuterBranch(ParseState *pstate,
/* push whereClause down to init part, taking care to avoid NULL in expr. */
quals = (Node *)startWithExpr;
Node* whereClauseCopy = (Node *)copyObject(whereClause);
if (whereClause != NULL) {
/* only join quals can be pushed down */
raw_expression_tree_walker((Node*)whereClauseCopy,
(bool (*)())walker_to_exclude_non_join_quals, (void*)NULL);
}
if (quals == NULL) {
/* pushdown requires deep copying of the quals */
quals = (Node *)copyObject(whereClause);
quals = whereClauseCopy;
} else if (whereClause != NULL) {
quals = (Node *)makeA_Expr(AEXPR_AND, NULL, (Node *)copyObject(whereClause),
quals = (Node *)makeA_Expr(AEXPR_AND, NULL, whereClauseCopy,
(Node*)startWithExpr, -1);
}

22
src/test/regress/expected/sw_bugfix-1.out
View File

@ -430,6 +430,7 @@ explain (costs off) select t1.ID,t1.VCH,pid,NAME,PTEX from TEST_HCB_FQB t1,TEST_
QUERY PLAN
----------------------------------------------------------------------------
CTE Scan on tmp_reuslt
Filter: ("t1@id" = "t2@id")
CTE tmp_reuslt
-> StartWith Operator
Start With pseudo atts: RUITR, array_key_1
@ -448,7 +449,7 @@ explain (costs off) select t1.ID,t1.VCH,pid,NAME,PTEX from TEST_HCB_FQB t1,TEST_
-> WorkTable Scan on tmp_reuslt
-> Hash
-> Seq Scan on test_hcb_fqb t1
(19 rows)
(20 rows)
CREATE OR REPLACE FUNCTION test_hcb_pro1(i_id in int) return int
AS
@ -1470,3 +1471,22 @@ DROP TABLE IF EXISTS start;
DROP TABLE IF EXISTS connect;
DROP TABLE IF EXISTS siblings;
DROP TABLE IF EXISTS prior;
-- test where clause pushdown result correctness
create table xt1(id int, lid int, name text);
create table xt2(idd int, lidd int, name text);
insert into xt1 values(1,null,'A'),(2,1,'B'),(3,2,'C');
insert into xt2 values(1,null,'A'),(2,1,'B'),(3,2,'C'), (4,3,'D');
select * from xt2,xt1 where xt1.id=xt2.idd and xt1.id!=2 start with id=2 connect by prior id=lid;
idd | lidd | name | id | lid | name
-----+------+------+----+-----+------
3 | 2 | C | 3 | 2 | C
(1 row)
select * from xt2,xt1 where xt1.id=xt2.idd and xt1.id=3 start with id=2 connect by prior id=lid;
idd | lidd | name | id | lid | name
-----+------+------+----+-----+------
3 | 2 | C | 3 | 2 | C
(1 row)
drop table if exists xt1;
drop table if exists xt2;

6
src/test/regress/expected/sw_icbc.out
View File

@ -477,6 +477,7 @@ explain (costs off) select * from t1, t2 where t1.id = t2.id start with t1.id =
QUERY PLAN
-----------------------------------------------------------------------------
CTE Scan on tmp_reuslt
Filter: ("t1@id" = "t2@id")
CTE tmp_reuslt
-> StartWith Operator
Start With pseudo atts: RUITR, array_key_1
@ -495,7 +496,7 @@ explain (costs off) select * from t1, t2 where t1.id = t2.id start with t1.id =
-> WorkTable Scan on tmp_reuslt
-> Hash
-> Seq Scan on t2
(19 rows)
(20 rows)
explain (costs off) select * from t1 join t2 on t1.id = t2.id start with t1.id = t2.id and t1.id = 1 connect by prior t1.id = t1.pid;
QUERY PLAN
@ -525,6 +526,7 @@ explain (costs off) select * from t1, (select * from t2) as test where t1.id = t
QUERY PLAN
-----------------------------------------------------------------------------
CTE Scan on tmp_reuslt
Filter: ("t1@id" = "test@id")
CTE tmp_reuslt
-> StartWith Operator
Start With pseudo atts: RUITR, array_key_1
@ -543,7 +545,7 @@ explain (costs off) select * from t1, (select * from t2) as test where t1.id = t
-> WorkTable Scan on tmp_reuslt
-> Hash
-> Seq Scan on t2
(19 rows)
(20 rows)
explain (costs off) select id, (select id from t2 start with t2.id = t1.id connect by t2.id = t1.id limit 1) from t1 where id = 1;
ERROR: START WITH CONNECT BY clauses must have at least one prior key.

10
src/test/regress/sql/sw_bugfix-1.sql
View File

@ -431,3 +431,13 @@ DROP TABLE IF EXISTS start;
DROP TABLE IF EXISTS connect;
DROP TABLE IF EXISTS siblings;
DROP TABLE IF EXISTS prior;
-- test where clause pushdown result correctness
create table xt1(id int, lid int, name text);
create table xt2(idd int, lidd int, name text);
insert into xt1 values(1,null,'A'),(2,1,'B'),(3,2,'C');
insert into xt2 values(1,null,'A'),(2,1,'B'),(3,2,'C'), (4,3,'D');
select * from xt2,xt1 where xt1.id=xt2.idd and xt1.id!=2 start with id=2 connect by prior id=lid;
select * from xt2,xt1 where xt1.id=xt2.idd and xt1.id=3 start with id=2 connect by prior id=lid;
drop table if exists xt1;
drop table if exists xt2;