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release-23.2: plpgsql: don't exit early when SELECT INTO returns no rows #115676

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Dec 6, 2023
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release-23.2: plpgsql: don't exit early when SELECT INTO returns no rows #115676

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88 changes: 88 additions & 0 deletions pkg/sql/logictest/testdata/logic_test/udf_plpgsql
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Original file line number Diff line number Diff line change
Expand Up @@ -1907,6 +1907,32 @@ SELECT f();
NOTICE: i = 104
NOTICE: i = 103

# When the SQL statement returns zero rows, the target variables are all set
# to NULL.
statement ok
CREATE OR REPLACE FUNCTION f() RETURNS INT AS $$
DECLARE
i INT := 0;
BEGIN
RAISE NOTICE 'i = %', i;
SELECT x INTO i FROM xy WHERE False;
RAISE NOTICE 'i = %', i;
i := 1;
RAISE NOTICE 'i = %', i;
INSERT INTO xy (SELECT 1, 2 FROM generate_series(1, 0)) RETURNING x INTO i;
RAISE NOTICE 'i = %', i;
RETURN 0;
END
$$ LANGUAGE PLpgSQL;

query T noticetrace
SELECT f();
----
NOTICE: i = 0
NOTICE: i = <NULL>
NOTICE: i = 1
NOTICE: i = <NULL>

statement error pgcode 0A000 pq: unimplemented: assigning to a variable more than once in the same INTO statement is not supported
CREATE OR REPLACE FUNCTION f() RETURNS INT AS $$
DECLARE
Expand Down Expand Up @@ -2730,4 +2756,66 @@ SELECT f();
----
1

# Regression test for #114826 - PLpgSQL routines should not prematurely exit
# when a SELECT INTO statement returns no rows.
subtest no_row_select_into

statement ok
CREATE TABLE t114826 (a INT);

statement ok
CREATE FUNCTION f114826() RETURNS INT AS $$
DECLARE
found INT;
BEGIN
RAISE NOTICE 'HERE 1';
SELECT a INTO found FROM t114826 WHERE a = 3;
RAISE NOTICE 'HERE 2';
INSERT INTO t114826 (SELECT * FROM t114826) RETURNING a INTO found;
RAISE NOTICE 'HERE 3';
RETURN 10;
END
$$ LANGUAGE PLpgSQL;

query T noticetrace
SELECT f114826();
----
NOTICE: HERE 1
NOTICE: HERE 2
NOTICE: HERE 3

query I
SELECT f114826();
----
10

statement ok
INSERT INTO t114826 VALUES (1);

query T noticetrace
SELECT f114826();
----
NOTICE: HERE 1
NOTICE: HERE 2
NOTICE: HERE 3

query I
SELECT * FROM t114826;
----
1
1

query I
SELECT f114826();
----
10

query I
SELECT * FROM t114826;
----
1
1
1
1

subtest end
5 changes: 1 addition & 4 deletions pkg/sql/opt/norm/decorrelate_funcs.go
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Expand Up @@ -742,10 +742,7 @@ func (c *CustomFuncs) ConstructBinary(op opt.Operator, left, right opt.ScalarExp
// ConstructNoColsRow returns a Values operator having a single row with zero
// columns.
func (c *CustomFuncs) ConstructNoColsRow() memo.RelExpr {
return c.f.ConstructValues(memo.ScalarListWithEmptyTuple, &memo.ValuesPrivate{
Cols: opt.ColList{},
ID: c.f.Metadata().NextUniqueID(),
})
return c.f.ConstructNoColsRow()
}

// referenceSingleColumn returns a Variable operator that refers to the one and
Expand Down
8 changes: 8 additions & 0 deletions pkg/sql/opt/norm/factory.go
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Expand Up @@ -464,6 +464,14 @@ func (f *Factory) ConstructZeroValues() memo.RelExpr {
})
}

// ConstructNoColsRow constructs a Values operator with no columns and one row.
func (f *Factory) ConstructNoColsRow() memo.RelExpr {
return f.ConstructValues(memo.ScalarListWithEmptyTuple, &memo.ValuesPrivate{
Cols: opt.ColList{},
ID: f.Metadata().NextUniqueID(),
})
}

// ConstructJoin constructs the join operator that corresponds to the given join
// operator type.
func (f *Factory) ConstructJoin(
Expand Down
5 changes: 1 addition & 4 deletions pkg/sql/opt/norm/factory_test.go
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Expand Up @@ -50,10 +50,7 @@ func TestSimplifyFilters(t *testing.T) {
eq := f.ConstructEq(variable, constant)

// Filters expression evaluates to False if any operand is False.
vals := f.ConstructValues(memo.ScalarListWithEmptyTuple, &memo.ValuesPrivate{
Cols: opt.ColList{},
ID: f.Metadata().NextUniqueID(),
})
vals := f.ConstructNoColsRow()
filters := memo.FiltersExpr{
f.ConstructFiltersItem(eq),
f.ConstructFiltersItem(memo.FalseSingleton),
Expand Down
5 changes: 1 addition & 4 deletions pkg/sql/opt/optbuilder/insert.go
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Expand Up @@ -566,10 +566,7 @@ func (mb *mutationBuilder) buildInputForInsert(inScope *scope, inputRows *tree.S
// Handle DEFAULT VALUES case by creating a single empty row as input.
if inputRows == nil {
mb.outScope = inScope.push()
mb.outScope.expr = mb.b.factory.ConstructValues(memo.ScalarListWithEmptyTuple, &memo.ValuesPrivate{
Cols: opt.ColList{},
ID: mb.md.NextUniqueID(),
})
mb.outScope.expr = mb.b.factory.ConstructNoColsRow()
mb.inputForInsertExpr = mb.outScope.expr
return
}
Expand Down
17 changes: 12 additions & 5 deletions pkg/sql/opt/optbuilder/plpgsql.go
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Original file line number Diff line number Diff line change
Expand Up @@ -507,13 +507,23 @@ func (b *plpgsqlBuilder) buildPLpgSQLStatements(stmts []ast.Statement, s *scope)
retCon := b.makeContinuation("_stmt_exec_ret")
b.appendPlpgSQLStmts(&retCon, stmts[i+1:])

// We only need the first row from the SQL statement.
// Ensure that the SQL statement returns at most one row.
stmtScope.expr = b.ob.factory.ConstructLimit(
stmtScope.expr,
b.ob.factory.ConstructConst(tree.NewDInt(tree.DInt(1)), types.Int),
stmtScope.makeOrderingChoice(),
)

// Ensure that the SQL statement returns at least one row. The RIGHT join
// ensures that when the SQL statement returns no rows, it is extended
// with a single row of NULL values.
stmtScope.expr = b.ob.factory.ConstructRightJoin(
stmtScope.expr,
b.ob.factory.ConstructNoColsRow(),
nil, /* on */
memo.EmptyJoinPrivate,
)

// Step 2: build the INTO statement into a continuation routine that calls
// the previously built continuation.
intoScope := b.buildInto(stmtScope, t.Target)
Expand Down Expand Up @@ -1384,10 +1394,7 @@ func (b *plpgsqlBuilder) resolveVariableForAssign(name tree.Name) *types.T {

func (b *plpgsqlBuilder) ensureScopeHasExpr(s *scope) {
if s.expr == nil {
s.expr = b.ob.factory.ConstructValues(memo.ScalarListWithEmptyTuple, &memo.ValuesPrivate{
Cols: opt.ColList{},
ID: b.ob.factory.Metadata().NextUniqueID(),
})
s.expr = b.ob.factory.ConstructNoColsRow()
}
}

Expand Down
5 changes: 1 addition & 4 deletions pkg/sql/opt/optbuilder/select.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1289,10 +1289,7 @@ func (b *Builder) buildFrom(
outScope = b.buildFromTables(from.Tables, lockCtx, inScope)
} else {
outScope = inScope.push()
outScope.expr = b.factory.ConstructValues(memo.ScalarListWithEmptyTuple, &memo.ValuesPrivate{
Cols: opt.ColList{},
ID: b.factory.Metadata().NextUniqueID(),
})
outScope.expr = b.factory.ConstructNoColsRow()
}

return outScope
Expand Down
5 changes: 1 addition & 4 deletions pkg/sql/opt/optbuilder/srfs.go
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Original file line number Diff line number Diff line change
Expand Up @@ -177,10 +177,7 @@ func (b *Builder) buildZip(exprs tree.Exprs, inScope *scope) (outScope *scope) {
}

// Construct the zip as a ProjectSet with empty input.
input := b.factory.ConstructValues(memo.ScalarListWithEmptyTuple, &memo.ValuesPrivate{
Cols: opt.ColList{},
ID: b.factory.Metadata().NextUniqueID(),
})
input := b.factory.ConstructNoColsRow()
outScope.expr = b.factory.ConstructProjectSet(input, zip)
if len(outScope.cols) == 1 {
outScope.singleSRFColumn = true
Expand Down
37 changes: 21 additions & 16 deletions pkg/sql/opt/optbuilder/testdata/procedure_plpgsql
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Expand Up @@ -55,23 +55,28 @@ call
│ └── project
│ ├── columns: "_stmt_exec_ret_2":58
│ ├── project
│ │ ├── columns: c:57!null
│ │ ├── limit
│ │ │ ├── columns: count_rows:14!null
│ │ │ ├── scalar-group-by
│ │ ├── columns: c:57
│ │ ├── right-join (cross)
│ │ │ ├── columns: count_rows:14
│ │ │ ├── limit
│ │ │ │ ├── columns: count_rows:14!null
│ │ │ │ ├── project
│ │ │ │ │ └── select
│ │ │ │ │ ├── columns: k:9!null i:10 s:11 crdb_internal_mvcc_timestamp:12 tableoid:13
│ │ │ │ │ ├── scan t
│ │ │ │ │ │ └── columns: k:9!null i:10 s:11 crdb_internal_mvcc_timestamp:12 tableoid:13
│ │ │ │ │ └── filters
│ │ │ │ │ └── eq
│ │ │ │ │ ├── variable: k:9
│ │ │ │ │ └── variable: arg_k:6
│ │ │ │ └── aggregations
│ │ │ │ └── count-rows [as=count_rows:14]
│ │ │ └── const: 1
│ │ │ │ ├── scalar-group-by
│ │ │ │ │ ├── columns: count_rows:14!null
│ │ │ │ │ ├── project
│ │ │ │ │ │ └── select
│ │ │ │ │ │ ├── columns: k:9!null i:10 s:11 crdb_internal_mvcc_timestamp:12 tableoid:13
│ │ │ │ │ │ ├── scan t
│ │ │ │ │ │ │ └── columns: k:9!null i:10 s:11 crdb_internal_mvcc_timestamp:12 tableoid:13
│ │ │ │ │ │ └── filters
│ │ │ │ │ │ └── eq
│ │ │ │ │ │ ├── variable: k:9
│ │ │ │ │ │ └── variable: arg_k:6
│ │ │ │ │ └── aggregations
│ │ │ │ │ └── count-rows [as=count_rows:14]
│ │ │ │ └── const: 1
│ │ │ ├── values
│ │ │ │ └── tuple
│ │ │ └── filters (true)
│ │ └── projections
│ │ └── variable: count_rows:14 [as=c:57]
│ └── projections
Expand Down