chore: import upstream snapshot with attribution

server/ast/limit.go

@@ -0,0 +1,100 @@
+// Copyright 2023 Dolthub, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package ast
+
+import (
+	"github.com/cockroachdb/errors"
+	"github.com/dolthub/go-mysql-server/sql/expression"
+
+	vitess "github.com/dolthub/vitess/go/vt/sqlparser"
+
+	"github.com/dolthub/doltgresql/postgres/parser/sem/tree"
+	pgexprs "github.com/dolthub/doltgresql/server/expression"
+)
+
+// nodeLimit handles *tree.Limit nodes.
+func nodeLimit(ctx *Context, node *tree.Limit) (*vitess.Limit, error) {
+	if node == nil || ((node.Count == nil || node.Count == tree.NullLiteral{}) && (node.Offset == nil || node.Offset == tree.NullLiteral{})) {
+		return nil, nil
+	}
+	var count vitess.Expr
+	if !node.LimitAll {
+		var err error
+		count, err = nodeExpr(ctx, node.Count)
+		if err != nil {
+			return nil, err
+		}
+	}
+	offset, err := nodeExpr(ctx, node.Offset)
+	if err != nil {
+		return nil, err
+	}
+	// GMS is hardcoded to expect vitess.SQLVal for expressions such as `LIMIT 1 OFFSET 1`.
+	// We need to remove the hard dependency, but for now, we'll just convert our literals to a vitess.SQLVal.
+	if injectedExpr, ok := count.(vitess.InjectedExpr); ok {
+		if literal, ok := injectedExpr.Expression.(*expression.Literal); ok {
+			l := literal.Value()
+			limitValue, err := int64ValueForLimit(l)
+			if err != nil {
+				return nil, err
+			}
+
+			if limitValue < 0 {
+				return nil, errors.Errorf("LIMIT must be greater than or equal to 0")
+			}
+
+			count = pgexprs.ToVitessLiteral(literal)
+		}
+	}
+	if injectedExpr, ok := offset.(vitess.InjectedExpr); ok {
+		if literal, ok := injectedExpr.Expression.(*expression.Literal); ok {
+			o := literal.Value()
+			offsetVal, err := int64ValueForLimit(o)
+			if err != nil {
+				return nil, err
+			}
+
+			if offsetVal < 0 {
+				return nil, errors.Errorf("OFFSET must be greater than or equal to 0")
+			}
+
+			offset = pgexprs.ToVitessLiteral(literal)
+		}
+	}
+	return &vitess.Limit{
+		Offset:   offset,
+		Rowcount: count,
+	}, nil
+}
+
+// int64ValueForLimit converts a literal value to an int64
+func int64ValueForLimit(l any) (int64, error) {
+	var limitValue int64
+	switch l := l.(type) {
+	case int:
+		limitValue = int64(l)
+	case int32:
+		limitValue = int64(l)
+	case int64:
+		limitValue = l
+	case float64:
+		limitValue = int64(l)
+	case float32:
+		limitValue = int64(l)
+	default:
+		return 0, errors.Errorf("unsupported limit/offset value type %T", l)
+	}
+	return limitValue, nil
+}