Add FROM clause parsing for ATTACH TABLE

- Add FromPath field to AttachQuery AST
- Parse FROM 'path' after table name in ATTACH TABLE

Fixes 01721_engine_file_truncate_on_insert/stmt3

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: kyleconroy

ast/ast.go

@@ -767,6 +767,7 @@ type AttachQuery struct {
 	Database           string               `json:"database,omitempty"`
 	Table              string               `json:"table,omitempty"`
 	Dictionary         string               `json:"dictionary,omitempty"`
+	FromPath           string               `json:"from_path,omitempty"`     // FROM 'path' clause
 	Columns            []*ColumnDeclaration `json:"columns,omitempty"`
 	ColumnsPrimaryKey       []Expression         `json:"columns_primary_key,omitempty"`        // PRIMARY KEY in column list
 	HasEmptyColumnsPrimaryKey bool               `json:"has_empty_columns_primary_key,omitempty"` // TRUE if PRIMARY KEY () was seen with empty parens

parser/parser.go

@@ -7275,6 +7275,15 @@ func (p *Parser) parseAttach() *ast.AttachQuery {
 
 	_ = isMaterializedView
 
+	// Parse FROM clause: ATTACH TABLE name FROM 'path'
+	if p.currentIs(token.FROM) {
+		p.nextToken() // skip FROM
+		if p.currentIs(token.STRING) {
+			attach.FromPath = p.current.Value
+			p.nextToken()
+		}
+	}
+
 	// Parse column definitions for ATTACH TABLE name(col1 type, ...)
 	if !isDatabase && p.currentIs(token.LPAREN) {
 		p.nextToken()

parser/testdata/01721_engine_file_truncate_on_insert/metadata.json

@@ -1,5 +1 @@
-{
-  "explain_todo": {
-    "stmt3": true
-  }
-}
+{}