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planner: eliminate if null on non null column #7924

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merged 6 commits into from
Oct 17, 2018
Merged

planner: eliminate if null on non null column #7924

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8bd985f
eliminate if null on non null column
zhexuany Oct 16, 2018
4623f36
adding explain test
zhexuany Oct 17, 2018
7000f42
recursivly trim expression tree
zhexuany Oct 17, 2018
1e029ec
address reviewer's comment
zhexuany Oct 17, 2018
a0f0a7f
remove extra line
zhexuany Oct 17, 2018
10ca98d
Merge branch 'master' into eliminate_if_null_on_non_null_column
zz-jason Oct 17, 2018
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37 changes: 37 additions & 0 deletions cmd/explaintest/r/explain_easy.result
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Original file line number Diff line number Diff line change
Expand Up @@ -385,3 +385,40 @@ Projection_5 8000.00 root test.ta.a
└─TableReader_9 10000.00 root data:TableScan_8
└─TableScan_8 10000.00 cop table:ta, range:[-inf,+inf], keep order:false, stats:pseudo
rollback;
drop table if exists t;
create table t(a int, nb int not null, nc int not null);
explain select ifnull(a, 0) from t;
id count task operator info
Projection_3 10000.00 root ifnull(test.t.a, 0)
└─TableReader_5 10000.00 root data:TableScan_4
└─TableScan_4 10000.00 cop table:t, range:[-inf,+inf], keep order:false, stats:pseudo
explain select ifnull(nb, 0) from t;
id count task operator info
TableReader_5 10000.00 root data:TableScan_4
└─TableScan_4 10000.00 cop table:t, range:[-inf,+inf], keep order:false, stats:pseudo
explain select ifnull(nb, 0), ifnull(nc, 0) from t;
id count task operator info
TableReader_5 10000.00 root data:TableScan_4
└─TableScan_4 10000.00 cop table:t, range:[-inf,+inf], keep order:false, stats:pseudo
explain select ifnull(a, 0), ifnull(nb, 0) from t;
id count task operator info
Projection_3 10000.00 root ifnull(test.t.a, 0), test.t.nb
└─TableReader_5 10000.00 root data:TableScan_4
└─TableScan_4 10000.00 cop table:t, range:[-inf,+inf], keep order:false, stats:pseudo
explain select ifnull(nb, 0), ifnull(nb, 0) from t;
id count task operator info
Projection_3 10000.00 root test.t.nb, test.t.nb
└─TableReader_5 10000.00 root data:TableScan_4
└─TableScan_4 10000.00 cop table:t, range:[-inf,+inf], keep order:false, stats:pseudo
explain select 1+ifnull(nb, 0) from t;
id count task operator info
Projection_3 10000.00 root plus(1, test.t.nb)
└─TableReader_5 10000.00 root data:TableScan_4
└─TableScan_4 10000.00 cop table:t, range:[-inf,+inf], keep order:false, stats:pseudo
explain select 1+ifnull(a, 0) from t;
id count task operator info
Projection_3 10000.00 root plus(1, ifnull(test.t.a, 0))
└─TableReader_5 10000.00 root data:TableScan_4
└─TableScan_4 10000.00 cop table:t, range:[-inf,+inf], keep order:false, stats:pseudo
drop table if exists t;
drop table if exists t;
12 changes: 12 additions & 0 deletions cmd/explaintest/t/explain_easy.test
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Expand Up @@ -81,3 +81,15 @@ begin;
insert tb values ('1');
explain select * from ta where a = 1;
rollback;

# https://github.com/pingcap/tidb/issues/7918
drop table if exists t;
create table t(a int, nb int not null, nc int not null);
explain select ifnull(a, 0) from t;
explain select ifnull(nb, 0) from t;
explain select ifnull(nb, 0), ifnull(nc, 0) from t;
explain select ifnull(a, 0), ifnull(nb, 0) from t;
explain select ifnull(nb, 0), ifnull(nb, 0) from t;
explain select 1+ifnull(nb, 0) from t;
explain select 1+ifnull(a, 0) from t;
drop table if exists t;
32 changes: 32 additions & 0 deletions planner/core/logical_plan_builder.go
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Expand Up @@ -576,6 +576,37 @@ func (b *PlanBuilder) buildProjectionField(id, position int, field *ast.SelectFi
}
}

func eliminateIfNullOnNotNullCol(p LogicalPlan, expr expression.Expression) expression.Expression {
ds, isDs := p.(*DataSource)
if !isDs {
return expr
}

scalarExpr, isScalarFunc := expr.(*expression.ScalarFunction)
if !isScalarFunc {
return expr
}
exprChildren := scalarExpr.GetArgs()
for i := 0; i < len(exprChildren); i++ {
exprChildren[i] = eliminateIfNullOnNotNullCol(p, exprChildren[i])
}

if scalarExpr.FuncName.L != ast.Ifnull {
return expr
}
colRef, isColRef := exprChildren[0].(*expression.Column)
if !isColRef {
return expr
}

colInfo := model.FindColumnInfo(ds.Columns, colRef.ColName.L)
if !mysql.HasNotNullFlag(colInfo.Flag) {
return expr
}

return colRef
}

// buildProjection returns a Projection plan and non-aux columns length.
func (b *PlanBuilder) buildProjection(p LogicalPlan, fields []*ast.SelectField, mapper map[*ast.AggregateFuncExpr]int) (LogicalPlan, int, error) {
b.optFlag |= flagEliminateProjection
Expand All @@ -585,6 +616,7 @@ func (b *PlanBuilder) buildProjection(p LogicalPlan, fields []*ast.SelectField,
oldLen := 0
for _, field := range fields {
newExpr, np, err := b.rewrite(field.Expr, p, mapper, true)
newExpr = eliminateIfNullOnNotNullCol(p, newExpr)
if err != nil {
return nil, 0, errors.Trace(err)
}
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