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planner: Solve the problem that the parent query condition is pushed incorrectly when the setvar function is evaluated in the subquery.（#11622） #11624

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merged 6 commits into from
Sep 5, 2019
Merged

planner: Solve the problem that the parent query condition is pushed incorrectly when the setvar function is evaluated in the subquery.（#11622） #11624

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4136bbd
fix issue
lovewin99 Aug 5, 2019
02787de
Merge branch 'master' into fix-issue
lovewin99 Aug 16, 2019
1f8030e
fix issue
lovewin99 Aug 23, 2019
74e9d88
Merge branch 'master' into fix-issue
lovewin99 Sep 3, 2019
726554f
fix-issue
lovewin99 Sep 3, 2019
fe9df8a
Merge branch 'master' into fix-issue
sre-bot Sep 5, 2019
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21 changes: 21 additions & 0 deletions expression/chunk_executor.go
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Original file line number Diff line number Diff line change
Expand Up @@ -53,6 +53,27 @@ func HasGetSetVarFunc(expr Expression) bool {
return false
}

// HasAssignSetVarFunc checks whether an expression contains SetVar function and assign a value
func HasAssignSetVarFunc(expr Expression) bool {
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This check looks pretty ad-hoc, I prefer to push no condition down to Projection's child completely if p.Exprs contains SetVar or GetVar, because there seems like many hidden corner cases which would return wrong results. @zz-jason How do you think?

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If p.Exprs contains setvar and getvar and does not push down all the conditions, then many normal pushdowns will be ignored, which can have a large impact on performance in many cases. I think this kind of check just a subset of reject all pushdowns, which helps narrow down the problem without expanding the problem. @eurekaka @zz-jason How do you think?

scalaFunc, ok := expr.(*ScalarFunction)
if !ok {
return false
}
if scalaFunc.FuncName.L == ast.SetVar {
for _, arg := range scalaFunc.GetArgs() {
if _, ok := arg.(*ScalarFunction); ok {
return true
}
}
}
for _, arg := range scalaFunc.GetArgs() {
if HasAssignSetVarFunc(arg) {
return true
}
}
return false
}

// VectorizedExecute evaluates a list of expressions column by column and append their results to "output" Chunk.
func VectorizedExecute(ctx sessionctx.Context, exprs []Expression, iterator *chunk.Iterator4Chunk, output *chunk.Chunk) error {
for colID, expr := range exprs {
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17 changes: 17 additions & 0 deletions planner/core/integration_test.go
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Expand Up @@ -59,3 +59,20 @@ func (s *testIntegrationSuite) TestShowSubquery(c *C) {
"a varchar(10) YES <nil> ",
))
}

func (s *testIntegrationSuite) TestPpdWithSetVar(c *C) {
store, dom, err := newStoreWithBootstrap()
c.Assert(err, IsNil)
tk := testkit.NewTestKit(c, store)
defer func() {
dom.Close()
store.Close()
}()
tk.MustExec("use test")
tk.MustExec("drop table if exists t")
tk.MustExec("create table t(c1 int, c2 varchar(255))")
tk.MustExec("insert into t values(1,'a'),(2,'d'),(3,'c')")

tk.MustQuery("select t01.c1,t01.c2,t01.c3 from (select t1.*,@c3:=@c3+1 as c3 from (select t.*,@c3:=0 from t order by t.c1)t1)t01 where t01.c3=1 and t01.c2='d'").Check(testkit.Rows())
tk.MustQuery("select t01.c1,t01.c2,t01.c3 from (select t1.*,@c3:=@c3+1 as c3 from (select t.*,@c3:=0 from t order by t.c1)t1)t01 where t01.c3=2 and t01.c2='d'").Check(testkit.Rows("2 d 2"))
}
6 changes: 6 additions & 0 deletions planner/core/rule_predicate_push_down.go
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Expand Up @@ -326,6 +326,12 @@ func isNullRejected(ctx sessionctx.Context, schema *expression.Schema, expr expr
func (p *LogicalProjection) PredicatePushDown(predicates []expression.Expression) (ret []expression.Expression, retPlan LogicalPlan) {
canBePushed := make([]expression.Expression, 0, len(predicates))
canNotBePushed := make([]expression.Expression, 0, len(predicates))
for _, expr := range p.Exprs {
if expression.HasAssignSetVarFunc(expr) {
_, child := p.baseLogicalPlan.PredicatePushDown(nil)
return predicates, child
}
}
for _, cond := range predicates {
newFilter := expression.ColumnSubstitute(cond, p.Schema(), p.Exprs)
if !expression.HasGetSetVarFunc(newFilter) {
Expand Down