sql: mark functions as Immutable/Stable/Volatile as just Pure/Impure

This commit adds the "Volatile" argument to all function properties,
replacing the "Impure" definition. I've replaced all "Impure" checks
with "!= VolatilityImmutable` to give equivalent functionality for now -
we can enhance the folding and the like in a later commit. The planner
tweaks can come from someone more familiar with it :).

Also updated the pg_proc table, which should be the only visible user
change.

Release note (sql change): Populated the `pg_proc` table's `provolatile`
field based on the internal builtin volatility definition. This value
used to always be NULL.

pkg/ccl/changefeedccl/avro_test.go

@@ -79,7 +79,7 @@ func parseValues(tableDesc *sqlbase.TableDescriptor, values string) ([]sqlbase.E
 		for colIdx, expr := range rowTuple {
 			col := &tableDesc.Columns[colIdx]
 			typedExpr, err := sqlbase.SanitizeVarFreeExpr(
-				expr, col.Type, "avro", semaCtx, false /* allowImpure */)
+				expr, col.Type, "avro", semaCtx, false /* allowNonImmutable */)
 			if err != nil {
 				return nil, err
 			}

pkg/ccl/partitionccl/partition.go

@@ -93,7 +93,7 @@ func valueEncodePartitionTuple(
 
 		var semaCtx tree.SemaContext
 		typedExpr, err := sqlbase.SanitizeVarFreeExpr(expr, cols[i].Type, "partition",
-			&semaCtx, false /* allowImpure */)
+			&semaCtx, false /* allowNonImmutable */)
 		if err != nil {
 			return nil, err
 		}

pkg/internal/sqlsmith/scalar.go

@@ -370,7 +370,7 @@ func makeFunc(s *Smither, ctx Context, typ *types.T, refs colRefs) (tree.TypedEx
 		return nil, false
 	}
 	fn := fns[s.rnd.Intn(len(fns))]
-	if s.disableImpureFns && fn.def.Impure {
+	if s.disableNonImmutableFns && fn.def.Volatility != tree.VolatilityImmutable {
 		return nil, false
 	}
 	for _, ignore := range s.ignoreFNs {

pkg/internal/sqlsmith/sqlsmith.go

@@ -75,17 +75,17 @@ type Smither struct {
 	scalarExprWeights, boolExprWeights []scalarExprWeight
 	scalarExprSampler, boolExprSampler *scalarExprSampler
 
-	disableWith        bool
-	disableImpureFns   bool
-	disableLimits      bool
-	disableWindowFuncs bool
-	simpleDatums       bool
-	avoidConsts        bool
-	vectorizable       bool
-	outputSort         bool
-	postgres           bool
-	ignoreFNs          []*regexp.Regexp
-	complexity         float64
+	disableWith            bool
+	disableNonImmutableFns bool
+	disableLimits          bool
+	disableWindowFuncs     bool
+	simpleDatums           bool
+	avoidConsts            bool
+	vectorizable           bool
+	outputSort             bool
+	postgres               bool
+	ignoreFNs              []*regexp.Regexp
+	complexity             float64
 
 	bulkSrv     *httptest.Server
 	bulkFiles   map[string][]byte
@@ -268,9 +268,9 @@ var DisableWith = simpleOption("disable WITH", func(s *Smither) {
 	s.disableWith = true
 })
 
-// DisableImpureFns causes the Smither to disable impure functions.
-var DisableImpureFns = simpleOption("disable impure funcs", func(s *Smither) {
-	s.disableImpureFns = true
+// DisableNonImmutableFns causes the Smither to disable non-immutable functions.
+var DisableNonImmutableFns = simpleOption("disable non-immutable funcs", func(s *Smither) {
+	s.disableNonImmutableFns = true
 })
 
 // DisableCRDBFns causes the Smither to disable crdb_internal functions.
@@ -337,7 +337,7 @@ var OutputSort = simpleOption("output sort", func(s *Smither) {
 var CompareMode = multiOption(
 	"compare mode",
 	DisableMutations(),
-	DisableImpureFns(),
+	DisableNonImmutableFns(),
 	DisableCRDBFns(),
 	IgnoreFNs("^version"),
 	DisableLimits(),

pkg/sql/alter_table.go

@@ -965,7 +965,7 @@ func applyColumnMutation(
 		} else {
 			colDatumType := col.Type
 			expr, err := sqlbase.SanitizeVarFreeExpr(
-				t.Default, colDatumType, "DEFAULT", &params.p.semaCtx, true, /* allowImpure */
+				t.Default, colDatumType, "DEFAULT", &params.p.semaCtx, true, /* allowNonImmutable */
 			)
 			if err != nil {
 				return err

pkg/sql/create_table.go

@@ -2257,7 +2257,7 @@ func validateComputedColumn(
 		return err
 	}
 	if _, err := sqlbase.SanitizeVarFreeExpr(
-		replacedExpr, defType, "computed column", semaCtx, false, /* allowImpure */
+		replacedExpr, defType, "computed column", semaCtx, false, /* allowNonImmutable */
 	); err != nil {
 		return err
 	}
@@ -2327,7 +2327,7 @@ func MakeCheckConstraint(
 	}
 
 	if _, err := sqlbase.SanitizeVarFreeExpr(
-		expr, types.Bool, "CHECK", semaCtx, true, /* allowImpure */
+		expr, types.Bool, "CHECK", semaCtx, true, /* allowNonImmutable */
 	); err != nil {
 		return nil, err
 	}

pkg/sql/execute.go

@@ -43,7 +43,7 @@ func fillInPlaceholders(
 		}
 		typedExpr, err := sqlbase.SanitizeVarFreeExpr(
 			e, typ, "EXECUTE parameter", /* context */
-			&semaCtx, true /* allowImpure */)
+			&semaCtx, true /* allowNonImmutable */)
 		if err != nil {
 			return nil, pgerror.WithCandidateCode(err, pgcode.WrongObjectType)
 		}

pkg/sql/logictest/testdata/logic_test/pg_catalog

@@ -1353,14 +1353,14 @@ FROM pg_catalog.pg_proc
 WHERE proname='substring'
 ----
 proname    proisstrict  proretset  provolatile  proparallel
-substring  false        false      NULL         NULL
-substring  false        false      NULL         NULL
-substring  false        false      NULL         NULL
-substring  false        false      NULL         NULL
-substring  false        false      NULL         NULL
-substring  false        false      NULL         NULL
-substring  false        false      NULL         NULL
-substring  false        false      NULL         NULL
+substring  false        false      i            NULL
+substring  false        false      i            NULL
+substring  false        false      i            NULL
+substring  false        false      i            NULL
+substring  false        false      i            NULL
+substring  false        false      i            NULL
+substring  false        false      i            NULL
+substring  false        false      i            NULL
 
 query TIIOTTTT colnames
 SELECT proname, pronargs, pronargdefaults, prorettype, proargtypes, proallargtypes, proargmodes, proargdefaults
@@ -1408,6 +1408,30 @@ WHERE proname='json_extract_path'
 proname            provariadic  pronargs  prorettype  proargtypes  proargmodes
 json_extract_path  25           2         3802        3802 25      {i,v}
 
+# Check provolatile is set.
+query TT colnames
+SELECT proname, provolatile
+FROM pg_catalog.pg_proc
+WHERE proname IN ('random', 'current_timestamp', 'substring')
+----
+proname            provolatile
+current_timestamp  s
+current_timestamp  s
+current_timestamp  s
+current_timestamp  s
+current_timestamp  s
+current_timestamp  s
+random             v
+substring          i
+substring          i
+substring          i
+substring          i
+substring          i
+substring          i
+substring          i
+substring          i
+
+
 user testuser
 
 # Should be globally visible

pkg/sql/opt/bench/bench_test.go

@@ -511,7 +511,7 @@ func (h *harness) prepareUsingAPI(tb testing.TB) {
 			typ,
 			"", /* context */
 			&h.semaCtx,
-			true, /* allowImpure */
+			true, /* allowNonImmutable */
 		)
 		if err != nil {
 			tb.Fatalf("%v", err)

pkg/sql/opt/exec/execbuilder/scalar.go

@@ -623,7 +623,7 @@ func (v *fastIsConstVisitor) VisitPre(expr tree.Expr) (recurse bool, newExpr tre
 
 	switch t := expr.(type) {
 	case *tree.FuncExpr:
-		if t.IsImpure() {
+		if t.Volatility() != tree.VolatilityImmutable {
 			v.isConst = false
 			return false, expr
 		}

pkg/sql/opt/memo/logical_props_builder.go

@@ -1388,8 +1388,8 @@ func BuildSharedProps(e opt.Expr, shared *props.Shared) {
 		}
 
 	case *FunctionExpr:
-		if t.Properties.Impure {
-			// Impure functions can return different value on each call.
+		if t.Properties.Volatility != tree.VolatilityImmutable {
+			// Volatile functions can return different value on each call.
 			shared.CanHaveSideEffects = true
 		}
 

pkg/sql/opt/norm/norm_test.go

@@ -86,7 +86,7 @@ func TestRuleFunctionAssumption(t *testing.T) {
 			t.Errorf("could not find properties for function %s", name)
 			continue
 		}
-		if props.Impure {
+		if props.Volatility != tree.VolatilityImmutable {
 			t.Errorf("%s should not be folded because it is impure", name)
 		}
 		if props.Category == categorySystemInfo || props.Category == categoryDateAndTime {

pkg/sql/opt/norm/testdata/rules/comp

@@ -60,7 +60,7 @@ select
       ├── (i:2 + k:1) > 4 [outer=(1,2)]
       └── (i:2 * 2) >= 3 [outer=(2)]
 
-# Impure function should not be considered constant.
+# Volatile function should not be considered constant.
 norm expect-not=CommuteConstInequality
 SELECT * FROM a WHERE random()::int>a.i+a.i
 ----

pkg/sql/pg_catalog.go

@@ -2179,6 +2179,19 @@ CREATE TABLE pg_catalog.pg_proc (
 							argmodes = tree.DNull
 							variadicType = oidZero
 						}
+
+						var volatile byte
+						switch props.Volatility {
+						case tree.VolatilityImmutable:
+							volatile = 'i'
+						case tree.VolatilityStable:
+							volatile = 's'
+						case tree.VolatilityVolatile:
+							volatile = 'v'
+						default:
+							return errors.Newf("unexpected volatility %d on proname %s", props.Volatility, name)
+						}
+
 						err := addRow(
 							h.BuiltinOid(name, &builtin),            // oid
 							dName,                                   // proname
@@ -2192,11 +2205,11 @@ CREATE TABLE pg_catalog.pg_proc (
 							tree.MakeDBool(tree.DBool(isAggregate)), // proisagg
 							tree.MakeDBool(tree.DBool(isWindow)),    // proiswindow
 							tree.DBoolFalse,                         // prosecdef
-							tree.MakeDBool(tree.DBool(!props.Impure)), // proleakproof
-							tree.DBoolFalse,                      // proisstrict
-							tree.MakeDBool(tree.DBool(isRetSet)), // proretset
-							tree.DNull,                           // provolatile
-							tree.DNull,                           // proparallel
+							tree.MakeDBool(tree.DBool(props.Volatility != tree.VolatilityVolatile)), // proleakproof
+							tree.DBoolFalse,                                 // proisstrict
+							tree.MakeDBool(tree.DBool(isRetSet)),            // proretset
+							tree.NewDString(string(volatile)),               // provolatile
+							tree.DNull,                                      // proparallel
 							tree.NewDInt(tree.DInt(builtin.Types.Length())), // pronargs
 							tree.NewDInt(tree.DInt(0)),                      // pronargdefaults
 							retType,                                         // prorettype

pkg/sql/sem/builtins/aggregate_builtins.go

@@ -38,7 +38,7 @@ func initAggregateBuiltins() {
 			panic("duplicate builtin: " + k)
 		}
 
-		if !v.props.Impure {
+		if v.props.Volatility != tree.VolatilityVolatile {
 			panic(fmt.Sprintf("%s: aggregate functions should all be impure, found %v", k, v))
 		}
 		if v.props.Class != tree.AggregateClass {
@@ -68,7 +68,7 @@ func initAggregateBuiltins() {
 }
 
 func aggProps() tree.FunctionProperties {
-	return tree.FunctionProperties{Class: tree.AggregateClass, Impure: true}
+	return tree.FunctionProperties{Class: tree.AggregateClass, Volatility: tree.VolatilityVolatile}
 }
 
 func aggPropsNullableArgs() tree.FunctionProperties {
@@ -318,8 +318,16 @@ var aggregates = map[string]builtinDefinition{
 			"Aggregates values as a JSON or JSONB array."),
 	),
 
-	"json_object_agg":  makeBuiltin(tree.FunctionProperties{UnsupportedWithIssue: 33285, Class: tree.AggregateClass, Impure: true}),
-	"jsonb_object_agg": makeBuiltin(tree.FunctionProperties{UnsupportedWithIssue: 33285, Class: tree.AggregateClass, Impure: true}),
+	"json_object_agg": makeBuiltin(tree.FunctionProperties{
+		UnsupportedWithIssue: 33285,
+		Class:                tree.AggregateClass,
+		Volatility:           tree.VolatilityVolatile,
+	}),
+	"jsonb_object_agg": makeBuiltin(tree.FunctionProperties{
+		UnsupportedWithIssue: 33285,
+		Class:                tree.AggregateClass,
+		Volatility:           tree.VolatilityVolatile,
+	}),
 
 	AnyNotNull: makePrivate(makeBuiltin(aggProps(),
 		makeAggOverloadWithReturnType(