sql: Allow DEFAULT/ON UPDATE types that can be assignment-cast

Release note (sql change): A column's DEFAULT/ON UPDATE clause
can now have a type that differs from the column type,as long as
that type can be assignment-cast into the column's type. This
increases our PostgreSQL compatibility.

pkg/sql/catalog/tabledesc/table.go

@@ -24,6 +24,7 @@ import (
 	"github.com/cockroachdb/cockroach/pkg/sql/catalog/schemaexpr"
 	"github.com/cockroachdb/cockroach/pkg/sql/pgwire/pgcode"
 	"github.com/cockroachdb/cockroach/pkg/sql/pgwire/pgerror"
+	"github.com/cockroachdb/cockroach/pkg/sql/sem/cast"
 	"github.com/cockroachdb/cockroach/pkg/sql/sem/eval"
 	"github.com/cockroachdb/cockroach/pkg/sql/sem/tree"
 	"github.com/cockroachdb/cockroach/pkg/sql/sem/volatility"
@@ -145,13 +146,22 @@ func MakeColumnDefDescs(
 	col.Type = resType
 
 	if d.HasDefaultExpr() {
+		var innerErr error
 		// Verify the default expression type is compatible with the column type
 		// and does not contain invalid functions.
 		ret.DefaultExpr, err = schemaexpr.SanitizeVarFreeExpr(
 			ctx, d.DefaultExpr.Expr, resType, "DEFAULT", semaCtx, volatility.Volatile,
 		)
 		if err != nil {
-			return nil, err
+			// Check if the default expression type can be assignment-cast into the
+			// column type. If it can allow the default and column type to differ.
+			ret.DefaultExpr, innerErr = d.DefaultExpr.Expr.TypeCheck(ctx, semaCtx, types.Any)
+			if innerErr != nil {
+				return nil, err
+			}
+			if ok := cast.ValidCast(resType, ret.DefaultExpr.ResolvedType(), cast.ContextAssignment); !ok {
+				return nil, err
+			}
 		}
 
 		// Keep the type checked expression so that the type annotation gets
@@ -167,10 +177,20 @@ func MakeColumnDefDescs(
 	if d.HasOnUpdateExpr() {
 		// Verify the on update expression type is compatible with the column type
 		// and does not contain invalid functions.
+		var innerErr error
 		ret.OnUpdateExpr, err = schemaexpr.SanitizeVarFreeExpr(
 			ctx, d.OnUpdateExpr.Expr, resType, "ON UPDATE", semaCtx, volatility.Volatile,
 		)
 		if err != nil {
+			// Check if the on update expression type can be assignment-cast into the
+			// column type. If it can allow the default and column type to differ.
+			ret.OnUpdateExpr, innerErr = d.OnUpdateExpr.Expr.TypeCheck(ctx, semaCtx, types.Any)
+			if innerErr != nil {
+				return nil, err
+			}
+			if ok := cast.ValidCast(resType, ret.OnUpdateExpr.ResolvedType(), cast.ContextAssignment); !ok {
+				return nil, err
+			}
 			return nil, err
 		}
 

pkg/sql/logictest/testdata/logic_test/cast

@@ -1401,3 +1401,25 @@ select CASE WHEN false THEN 1::REGTYPE ELSE 2::REGNAMESPACE END;
 select CASE WHEN false THEN 1::REGTYPE ELSE 2::REGPROC END;
 select CASE WHEN false THEN 1::REGTYPE ELSE 2::REGPROCEDURE END;
 select CASE WHEN false THEN 1::REGTYPE ELSE 2::REGROLE END;
+
+
+# Test that default/on update expression differing from column type
+statement ok
+CREATE TABLE def_assn_cast (
+a INT4 DEFAULT 1.0::FLOAT4,
+b VARCHAR DEFAULT 'true'::BOOL,
+c NAME DEFAULT 'foo'::BPCHAR,
+d JSONB DEFAULT 'null'::CHAR,
+)
+
+# Due to cast context we support cases that Postgres doesn't
+statement ok
+CREATE TABLE nonpg_assn_cast (
+a BOOL DEFAULT 'foo',
+b JSONB DEFAULT 'null'::CHAR,
+)
+
+statement error pq: expected DEFAULT expression to have type ., but . has type .
+CREATE TABLE def_assn_cast (
+a INT4 DEFAULT 1.0::BOOL
+)