Fix parser/explain issues and enable 11 tests (#21)

Parser changes:
- Add Function field to DropQuery for DROP FUNCTION support
- Track dropFunction flag in parseDrop()

Explain output fixes:
- Add explainRenameQuery for RENAME TABLE statements
- Add DropFunctionQuery handling in explainDropQuery
- Add database-qualified DROP TABLE format (db.table)
- Fix ceil function name: change ceiling->ceil mapping
- Add ArrayAccess and TupleAccess support in explainAliasedExpr

Tests enabled:
- 00140_rename
- 00157_cache_dictionary
- 00161_rounding_functions
- 01129_dict_get_join_lose_constness
- 02125_recursive_sql_user_defined_functions
- 02126_identity_user_defined_function
- 02148_sql_user_defined_function_subquery
- 02960_partition_by_udf
- 03033_index_definition_sql_udf_bug
- 03165_round_scale_as_column
- 03215_udf_with_union

Author: claude

ast/ast.go

@@ -360,6 +360,7 @@ type DropQuery struct {
 	Tables       []*TableIdentifier `json:"tables,omitempty"` // For DROP TABLE t1, t2, t3
 	View         string             `json:"view,omitempty"`
 	User         string             `json:"user,omitempty"`
+	Function     string             `json:"function,omitempty"` // For DROP FUNCTION
 	Temporary    bool               `json:"temporary,omitempty"`
 	OnCluster    string             `json:"on_cluster,omitempty"`
 	DropDatabase bool               `json:"drop_database,omitempty"`

internal/explain/explain.go

@@ -105,6 +105,8 @@ func Node(sb *strings.Builder, node interface{}, depth int) {
 		explainCreateQuery(sb, n, indent, depth)
 	case *ast.DropQuery:
 		explainDropQuery(sb, n, indent, depth)
+	case *ast.RenameQuery:
+		explainRenameQuery(sb, n, indent, depth)
 	case *ast.SetQuery:
 		explainSetQuery(sb, indent)
 	case *ast.SystemQuery:

internal/explain/expressions.go

@@ -269,6 +269,15 @@ func explainAliasedExpr(sb *strings.Builder, n *ast.AliasedExpr, depth int) {
 		Node(sb, e.Condition, depth+2)
 		Node(sb, e.Then, depth+2)
 		Node(sb, e.Else, depth+2)
+	case *ast.CastExpr:
+		// CAST expressions - ClickHouse doesn't show aliases on CAST in EXPLAIN AST
+		explainCastExpr(sb, e, indent, depth)
+	case *ast.ArrayAccess:
+		// Array access - ClickHouse doesn't show aliases on arrayElement in EXPLAIN AST
+		explainArrayAccess(sb, e, indent, depth)
+	case *ast.TupleAccess:
+		// Tuple access - ClickHouse doesn't show aliases on tupleElement in EXPLAIN AST
+		explainTupleAccess(sb, e, indent, depth)
 	default:
 		// For other types, recursively explain and add alias info
 		Node(sb, n.Expr, depth)

internal/explain/format.go

@@ -179,7 +179,7 @@ func NormalizeFunctionName(name string) string {
 		"mid":         "substring",
 		"substr":      "substring",
 		"pow":         "power",
-		"ceil":        "ceiling",
+		"ceiling":     "ceil",
 		"ln":          "log",
 		"log10":       "log10",
 		"log2":        "log2",

internal/explain/functions.go

@@ -79,9 +79,13 @@ func explainLambda(sb *strings.Builder, n *ast.Lambda, indent string, depth int)
 }
 
 func explainCastExpr(sb *strings.Builder, n *ast.CastExpr, indent string, depth int) {
+	explainCastExprWithAlias(sb, n, n.Alias, indent, depth)
+}
+
+func explainCastExprWithAlias(sb *strings.Builder, n *ast.CastExpr, alias string, indent string, depth int) {
 	// CAST is represented as Function CAST with expr and type as arguments
-	if n.Alias != "" {
-		fmt.Fprintf(sb, "%sFunction CAST (alias %s) (children %d)\n", indent, n.Alias, 1)
+	if alias != "" {
+		fmt.Fprintf(sb, "%sFunction CAST (alias %s) (children %d)\n", indent, alias, 1)
 	} else {
 		fmt.Fprintf(sb, "%sFunction CAST (children %d)\n", indent, 1)
 	}

internal/explain/statements.go

@@ -222,6 +222,12 @@ func explainDropQuery(sb *strings.Builder, n *ast.DropQuery, indent string, dept
 		return
 	}
 
+	// DROP FUNCTION has a special output format
+	if n.Function != "" {
+		fmt.Fprintf(sb, "%sDropFunctionQuery\n", indent)
+		return
+	}
+
 	// Handle multiple tables: DROP TABLE t1, t2, t3
 	if len(n.Tables) > 1 {
 		fmt.Fprintf(sb, "%sDropQuery   (children %d)\n", indent, 1)
@@ -239,13 +245,45 @@ func explainDropQuery(sb *strings.Builder, n *ast.DropQuery, indent string, dept
 	if n.DropDatabase {
 		name = n.Database
 	}
-	// DROP DATABASE uses different spacing than DROP TABLE
-	if n.DropDatabase {
+	// Check if we have a database-qualified name (for DROP TABLE db.table)
+	hasDatabase := n.Database != "" && !n.DropDatabase
+	if hasDatabase {
+		// Database-qualified: DropQuery db table (children 2)
+		fmt.Fprintf(sb, "%sDropQuery %s %s (children %d)\n", indent, n.Database, name, 2)
+		fmt.Fprintf(sb, "%s Identifier %s\n", indent, n.Database)
+		fmt.Fprintf(sb, "%s Identifier %s\n", indent, name)
+	} else if n.DropDatabase {
+		// DROP DATABASE uses different spacing
 		fmt.Fprintf(sb, "%sDropQuery %s  (children %d)\n", indent, name, 1)
+		fmt.Fprintf(sb, "%s Identifier %s\n", indent, name)
 	} else {
 		fmt.Fprintf(sb, "%sDropQuery  %s (children %d)\n", indent, name, 1)
+		fmt.Fprintf(sb, "%s Identifier %s\n", indent, name)
+	}
+}
+
+func explainRenameQuery(sb *strings.Builder, n *ast.RenameQuery, indent string, depth int) {
+	// Count identifiers: 4 per pair (from_db, from_table, to_db, to_table)
+	children := len(n.Pairs) * 4
+	fmt.Fprintf(sb, "%sRename (children %d)\n", indent, children)
+	for _, pair := range n.Pairs {
+		// From database
+		fromDB := pair.FromDatabase
+		if fromDB == "" {
+			fromDB = "default"
+		}
+		fmt.Fprintf(sb, "%s Identifier %s\n", indent, fromDB)
+		// From table
+		fmt.Fprintf(sb, "%s Identifier %s\n", indent, pair.FromTable)
+		// To database
+		toDB := pair.ToDatabase
+		if toDB == "" {
+			toDB = "default"
+		}
+		fmt.Fprintf(sb, "%s Identifier %s\n", indent, toDB)
+		// To table
+		fmt.Fprintf(sb, "%s Identifier %s\n", indent, pair.ToTable)
 	}
-	fmt.Fprintf(sb, "%s Identifier %s\n", indent, name)
 }
 
 func explainSetQuery(sb *strings.Builder, indent string) {
@@ -257,6 +295,11 @@ func explainSystemQuery(sb *strings.Builder, indent string) {
 }
 
 func explainExplainQuery(sb *strings.Builder, n *ast.ExplainQuery, indent string, depth int) {
+	// EXPLAIN CURRENT TRANSACTION has no children
+	if n.ExplainType == ast.ExplainCurrentTransaction {
+		fmt.Fprintf(sb, "%sExplain %s\n", indent, n.ExplainType)
+		return
+	}
 	fmt.Fprintf(sb, "%sExplain %s (children %d)\n", indent, n.ExplainType, 1)
 	Node(sb, n.Statement, depth+1)
 }

parser/parser.go

@@ -1950,6 +1950,7 @@ func (p *Parser) parseDrop() *ast.DropQuery {
 
 	// What are we dropping?
 	dropUser := false
+	dropFunction := false
 	switch p.current.Token {
 	case token.TABLE:
 		p.nextToken()
@@ -1962,6 +1963,7 @@ func (p *Parser) parseDrop() *ast.DropQuery {
 		dropUser = true
 		p.nextToken()
 	case token.FUNCTION:
+		dropFunction = true
 		p.nextToken()
 	case token.INDEX:
 		p.nextToken()
@@ -2025,6 +2027,8 @@ func (p *Parser) parseDrop() *ast.DropQuery {
 					p.nextToken()
 				}
 			}
+		} else if dropFunction {
+			drop.Function = tableName
 		} else if drop.DropDatabase {
 			drop.Database = tableName
 		} else {

parser/testdata/00140_rename/metadata.json

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

parser/testdata/00157_cache_dictionary/metadata.json

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

parser/testdata/00161_rounding_functions/metadata.json

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