Add YYYY support for EXTRACT and fix alias handling

- Added YYYY as an alias for YEAR in EXTRACT field parsing
- ExtractExpr now properly uses its Alias field for EXPLAIN output
- Added ExtractExpr case in explainAliasedExpr for alias wrapping

Fixes 00619_extract test.

Author: claude

internal/explain/expressions.go

@@ -529,6 +529,9 @@ func explainAliasedExpr(sb *strings.Builder, n *ast.AliasedExpr, depth int) {
 	case *ast.Lambda:
 		// Lambda expressions with alias
 		explainLambdaWithAlias(sb, e, n.Alias, indent, depth)
+	case *ast.ExtractExpr:
+		// EXTRACT expressions with alias
+		explainExtractExprWithAlias(sb, e, n.Alias, indent, depth)
 	case *ast.Identifier:
 		// Identifiers with alias
 		fmt.Fprintf(sb, "%sIdentifier %s (alias %s)\n", indent, e.Name(), escapeAlias(n.Alias))

internal/explain/functions.go

@@ -882,10 +882,23 @@ func explainExistsExpr(sb *strings.Builder, n *ast.ExistsExpr, indent string, de
 }
 
 func explainExtractExpr(sb *strings.Builder, n *ast.ExtractExpr, indent string, depth int) {
+	explainExtractExprWithAlias(sb, n, n.Alias, indent, depth)
+}
+
+func explainExtractExprWithAlias(sb *strings.Builder, n *ast.ExtractExpr, alias string, indent string, depth int) {
 	// EXTRACT is represented as Function toYear, toMonth, etc.
 	// ClickHouse uses specific function names for date/time extraction
 	fnName := extractFieldToFunction(n.Field)
-	fmt.Fprintf(sb, "%sFunction %s (children %d)\n", indent, fnName, 1)
+	// Use alias from parameter, or fall back to expression's alias
+	effectiveAlias := alias
+	if effectiveAlias == "" {
+		effectiveAlias = n.Alias
+	}
+	if effectiveAlias != "" {
+		fmt.Fprintf(sb, "%sFunction %s (alias %s) (children %d)\n", indent, fnName, effectiveAlias, 1)
+	} else {
+		fmt.Fprintf(sb, "%sFunction %s (children %d)\n", indent, fnName, 1)
+	}
 	fmt.Fprintf(sb, "%s ExpressionList (children %d)\n", indent, 1)
 	Node(sb, n.From, depth+2)
 }
@@ -897,7 +910,7 @@ func extractFieldToFunction(field string) string {
 		return "toDayOfMonth"
 	case "MONTH":
 		return "toMonth"
-	case "YEAR":
+	case "YEAR", "YYYY":
 		return "toYear"
 	case "SECOND":
 		return "toSecond"

parser/expression.go

@@ -1282,7 +1282,7 @@ func (p *Parser) parseExtract() ast.Expression {
 		field := strings.ToUpper(p.current.Value)
 		// Check if it's a known date/time field
 		dateTimeFields := map[string]bool{
-			"YEAR": true, "QUARTER": true, "MONTH": true, "WEEK": true,
+			"YEAR": true, "YYYY": true, "QUARTER": true, "MONTH": true, "WEEK": true,
 			"DAY": true, "DAYOFWEEK": true, "DAYOFYEAR": true,
 			"HOUR": true, "MINUTE": true, "SECOND": true,
 			"TIMEZONE_HOUR": true, "TIMEZONE_MINUTE": true,

parser/testdata/00619_extract/metadata.json

@@ -1,5 +1 @@
-{
-  "explain_todo": {
-    "stmt13": true
-  }
-}
+{}

parser/testdata/01095_tpch_like_smoke/metadata.json

@@ -7,7 +7,6 @@
     "stmt30": true,
     "stmt32": true,
     "stmt34": true,
-    "stmt36": true,
     "stmt38": true,
     "stmt42": true,
     "stmt46": true,