Fix 4 parser tests with EXPLAIN AST improvements

internal/explain/explain.go

@@ -131,6 +131,8 @@ func Node(sb *strings.Builder, node interface{}, depth int) {
 		explainUseQuery(sb, n, indent)
 	case *ast.DescribeQuery:
 		explainDescribeQuery(sb, n, indent)
+	case *ast.ExistsQuery:
+		explainExistsTableQuery(sb, n, indent)
 
 	// Types
 	case *ast.DataType:

internal/explain/functions.go

@@ -800,12 +800,38 @@ func explainExistsExpr(sb *strings.Builder, n *ast.ExistsExpr, indent string, de
 
 func explainExtractExpr(sb *strings.Builder, n *ast.ExtractExpr, indent string, depth int) {
 	// EXTRACT is represented as Function toYear, toMonth, etc.
-	fnName := "to" + strings.Title(strings.ToLower(n.Field))
+	// ClickHouse uses specific function names for date/time extraction
+	fnName := extractFieldToFunction(n.Field)
 	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)
 }
 
+// extractFieldToFunction maps EXTRACT field names to ClickHouse function names
+func extractFieldToFunction(field string) string {
+	switch strings.ToUpper(field) {
+	case "DAY":
+		return "toDayOfMonth"
+	case "MONTH":
+		return "toMonth"
+	case "YEAR":
+		return "toYear"
+	case "SECOND":
+		return "toSecond"
+	case "MINUTE":
+		return "toMinute"
+	case "HOUR":
+		return "toHour"
+	case "QUARTER":
+		return "toQuarter"
+	case "WEEK":
+		return "toWeek"
+	default:
+		// Fallback to generic "to" + TitleCase(field)
+		return "to" + strings.Title(strings.ToLower(field))
+	}
+}
+
 func explainWindowSpec(sb *strings.Builder, n *ast.WindowSpec, indent string, depth int) {
 	// Window spec is represented as WindowDefinition
 	// For simple cases like OVER (), just output WindowDefinition without children

internal/explain/select.go

@@ -175,6 +175,9 @@ func explainOrderByElement(sb *strings.Builder, n *ast.OrderByElement, indent st
 		if n.FillStep != nil {
 			children++
 		}
+		if n.Collate != "" {
+			children++
+		}
 		fmt.Fprintf(sb, "%sOrderByElement (children %d)\n", indent, children)
 		Node(sb, n.Expression, depth+1)
 		if n.FillFrom != nil {
@@ -186,6 +189,10 @@ func explainOrderByElement(sb *strings.Builder, n *ast.OrderByElement, indent st
 		if n.FillStep != nil {
 			Node(sb, n.FillStep, depth+1)
 		}
+		if n.Collate != "" {
+			// COLLATE is output as a string literal
+			fmt.Fprintf(sb, "%s Literal \\'%s\\'\n", indent, n.Collate)
+		}
 	}
 }
 

internal/explain/statements.go

@@ -363,6 +363,13 @@ func explainShowQuery(sb *strings.Builder, n *ast.ShowQuery, indent string) {
 		showType = "Tables"
 	}
 
+	// SHOW CREATE DATABASE has special output format
+	if n.ShowType == ast.ShowCreateDB && n.From != "" {
+		fmt.Fprintf(sb, "%sShowCreateDatabaseQuery %s  (children 1)\n", indent, n.From)
+		fmt.Fprintf(sb, "%s Identifier %s\n", indent, n.From)
+		return
+	}
+
 	// SHOW CREATE TABLE has special output format with database and table identifiers
 	if n.ShowType == ast.ShowCreate && (n.Database != "" || n.From != "") {
 		// Format: ShowCreateTableQuery database table (children 2)
@@ -383,11 +390,19 @@ func explainShowQuery(sb *strings.Builder, n *ast.ShowQuery, indent string) {
 		return
 	}
 
+	// SHOW TABLES FROM database - include database as child
+	if n.ShowType == ast.ShowTables && n.From != "" {
+		fmt.Fprintf(sb, "%sShowTables (children 1)\n", indent)
+		fmt.Fprintf(sb, "%s Identifier %s\n", indent, n.From)
+		return
+	}
+
 	fmt.Fprintf(sb, "%sShow%s\n", indent, showType)
 }
 
 func explainUseQuery(sb *strings.Builder, n *ast.UseQuery, indent string) {
-	fmt.Fprintf(sb, "%sUse %s\n", indent, n.Database)
+	fmt.Fprintf(sb, "%sUseQuery %s (children %d)\n", indent, n.Database, 1)
+	fmt.Fprintf(sb, "%s Identifier %s\n", indent, n.Database)
 }
 
 func explainDescribeQuery(sb *strings.Builder, n *ast.DescribeQuery, indent string) {
@@ -422,6 +437,19 @@ func explainDescribeQuery(sb *strings.Builder, n *ast.DescribeQuery, indent stri
 	}
 }
 
+func explainExistsTableQuery(sb *strings.Builder, n *ast.ExistsQuery, indent string) {
+	// EXISTS TABLE/DATABASE/DICTIONARY query
+	name := n.Table
+	if n.Database != "" {
+		name = n.Database + " " + n.Table
+	}
+	fmt.Fprintf(sb, "%sExistsTableQuery %s (children %d)\n", indent, name, 2)
+	if n.Database != "" {
+		fmt.Fprintf(sb, "%s Identifier %s\n", indent, n.Database)
+	}
+	fmt.Fprintf(sb, "%s Identifier %s\n", indent, n.Table)
+}
+
 func explainDataType(sb *strings.Builder, n *ast.DataType, indent string, depth int) {
 	// If type has parameters, expand them as children
 	if len(n.Parameters) > 0 {

parser/testdata/00619_extract/metadata.json

@@ -1 +1 @@
-{"todo": true}
+{}

parser/testdata/00950_dict_get/metadata.json

@@ -1 +1 @@
-{"todo": true}
+{}

parser/testdata/01048_exists_query/metadata.json

@@ -1 +1 @@
-{"todo": true}
+{}

parser/testdata/01161_information_schema/metadata.json

@@ -1 +1 @@
-{"todo": true}
+{}

parser/testdata/01354_order_by_tuple_collate_const/metadata.json

@@ -1 +1 @@
-{"todo": true}
+{}

parser/testdata/02206_information_schema_show_database/metadata.json

@@ -1 +1 @@
-{"todo": true}
+{}