Add SHOW INDEX parsing and escape single quotes in identifiers

- Add parsing for SHOW INDEX/INDEXES/INDICES/KEYS statements
  Maps to ShowColumns type as ClickHouse does internally
- Handle SHOW EXTENDED INDEX syntax
- Handle SHOW INDEX FROM table FROM database syntax
- Add EscapeIdentifier function to escape single quotes as \'
- Apply escaping to DropQuery and CreateQuery output

Fixes 02724_show_indexes and related tests.

Author: claude

internal/explain/format.go

@@ -37,6 +37,12 @@ func FormatFloat(val float64) string {
 	return strconv.FormatFloat(val, 'f', -1, 64)
 }
 
+// EscapeIdentifier escapes single quotes in identifiers for EXPLAIN AST output
+// ClickHouse escapes ' as \' in identifier names
+func EscapeIdentifier(s string) string {
+	return strings.ReplaceAll(s, "'", "\\'")
+}
+
 // escapeStringLiteral escapes special characters in a string for EXPLAIN AST output
 // Uses double-escaping as ClickHouse EXPLAIN AST displays strings
 // Iterates over bytes to preserve raw bytes (including invalid UTF-8)

internal/explain/statements.go

@@ -179,16 +179,16 @@ func explainCreateQuery(sb *strings.Builder, n *ast.CreateQuery, indent string,
 	}
 	// ClickHouse adds an extra space before (children N) for CREATE DATABASE
 	if n.CreateDatabase {
-		fmt.Fprintf(sb, "%sCreateQuery %s  (children %d)\n", indent, name, children)
-		fmt.Fprintf(sb, "%s Identifier %s\n", indent, name)
+		fmt.Fprintf(sb, "%sCreateQuery %s  (children %d)\n", indent, EscapeIdentifier(name), children)
+		fmt.Fprintf(sb, "%s Identifier %s\n", indent, EscapeIdentifier(name))
 	} else if hasDatabase {
 		// Database-qualified: CreateQuery db table (children N)
-		fmt.Fprintf(sb, "%sCreateQuery %s %s (children %d)\n", indent, n.Database, name, children)
-		fmt.Fprintf(sb, "%s Identifier %s\n", indent, n.Database)
-		fmt.Fprintf(sb, "%s Identifier %s\n", indent, name)
+		fmt.Fprintf(sb, "%sCreateQuery %s %s (children %d)\n", indent, EscapeIdentifier(n.Database), EscapeIdentifier(name), children)
+		fmt.Fprintf(sb, "%s Identifier %s\n", indent, EscapeIdentifier(n.Database))
+		fmt.Fprintf(sb, "%s Identifier %s\n", indent, EscapeIdentifier(name))
 	} else {
-		fmt.Fprintf(sb, "%sCreateQuery %s (children %d)\n", indent, name, children)
-		fmt.Fprintf(sb, "%s Identifier %s\n", indent, name)
+		fmt.Fprintf(sb, "%sCreateQuery %s (children %d)\n", indent, EscapeIdentifier(name), children)
+		fmt.Fprintf(sb, "%s Identifier %s\n", indent, EscapeIdentifier(name))
 	}
 	if len(n.Columns) > 0 || len(n.Indexes) > 0 || len(n.Projections) > 0 || len(n.Constraints) > 0 {
 		childrenCount := 0
@@ -492,16 +492,16 @@ func explainDropQuery(sb *strings.Builder, n *ast.DropQuery, indent string, dept
 	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)
+		fmt.Fprintf(sb, "%sDropQuery %s %s (children %d)\n", indent, EscapeIdentifier(n.Database), EscapeIdentifier(name), 2)
+		fmt.Fprintf(sb, "%s Identifier %s\n", indent, EscapeIdentifier(n.Database))
+		fmt.Fprintf(sb, "%s Identifier %s\n", indent, EscapeIdentifier(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)
+		fmt.Fprintf(sb, "%sDropQuery %s  (children %d)\n", indent, EscapeIdentifier(name), 1)
+		fmt.Fprintf(sb, "%s Identifier %s\n", indent, EscapeIdentifier(name))
 	} else {
-		fmt.Fprintf(sb, "%sDropQuery  %s (children %d)\n", indent, name, 1)
-		fmt.Fprintf(sb, "%s Identifier %s\n", indent, name)
+		fmt.Fprintf(sb, "%sDropQuery  %s (children %d)\n", indent, EscapeIdentifier(name), 1)
+		fmt.Fprintf(sb, "%s Identifier %s\n", indent, EscapeIdentifier(name))
 	}
 }
 

parser/parser.go

@@ -4549,6 +4549,10 @@ func (p *Parser) parseShow() ast.Statement {
 	case token.COLUMNS:
 		show.ShowType = ast.ShowColumns
 		p.nextToken()
+	case token.INDEX:
+		// SHOW INDEX FROM table - treat as ShowColumns (ClickHouse maps to ShowColumns)
+		show.ShowType = ast.ShowColumns
+		p.nextToken()
 	case token.CREATE:
 		p.nextToken()
 		if p.currentIs(token.DATABASE) {
@@ -4625,11 +4629,25 @@ func (p *Parser) parseShow() ast.Statement {
 				show.ShowType = ast.ShowDictionaries
 			case "FUNCTIONS":
 				show.ShowType = ast.ShowFunctions
+			case "INDEXES", "INDICES", "KEYS":
+				// SHOW INDEXES/INDICES/KEYS FROM table - treat as ShowColumns
+				show.ShowType = ast.ShowColumns
+			case "EXTENDED":
+				// SHOW EXTENDED INDEX FROM table - treat as ShowColumns
+				p.nextToken()
+				if p.currentIs(token.INDEX) {
+					p.nextToken()
+				}
+				show.ShowType = ast.ShowColumns
+				// Don't consume another token, fall through to FROM parsing
+				goto parseFrom
 			}
 			p.nextToken()
 		}
 	}
 
+parseFrom:
+
 	// Parse FROM clause (or table/database name for SHOW CREATE TABLE/DATABASE/DICTIONARY/VIEW)
 	showCreateTypes := show.ShowType == ast.ShowCreate || show.ShowType == ast.ShowCreateDB || show.ShowType == ast.ShowCreateDictionary || show.ShowType == ast.ShowCreateView
 	if p.currentIs(token.FROM) || (showCreateTypes && (p.currentIs(token.IDENT) || p.current.Token.IsKeyword())) {
@@ -4653,6 +4671,15 @@ func (p *Parser) parseShow() ast.Statement {
 		}
 	}
 
+	// Handle SHOW INDEX FROM table FROM database syntax (second FROM for database)
+	if p.currentIs(token.FROM) && show.ShowType == ast.ShowColumns {
+		p.nextToken()
+		if p.currentIs(token.IDENT) || p.current.Token.IsKeyword() {
+			show.Database = p.current.Value
+			p.nextToken()
+		}
+	}
+
 	// Parse NOT LIKE, LIKE or ILIKE clause
 	if p.currentIs(token.NOT) {
 		p.nextToken()

parser/testdata/02706_show_columns/metadata.json

@@ -1,13 +1,7 @@
 {
   "explain_todo": {
     "stmt2": true,
-    "stmt35": true,
-    "stmt36": true,
-    "stmt37": true,
-    "stmt40": true,
-    "stmt41": true,
     "stmt5": true,
-    "stmt7": true,
     "stmt9": true
   }
 }

parser/testdata/02724_show_indexes/metadata.json

@@ -1,23 +1 @@
-{
-  "explain_todo": {
-    "stmt11": true,
-    "stmt15": true,
-    "stmt19": true,
-    "stmt23": true,
-    "stmt25": true,
-    "stmt26": true,
-    "stmt27": true,
-    "stmt28": true,
-    "stmt29": true,
-    "stmt30": true,
-    "stmt31": true,
-    "stmt37": true,
-    "stmt39": true,
-    "stmt4": true,
-    "stmt41": true,
-    "stmt5": true,
-    "stmt6": true,
-    "stmt7": true,
-    "stmt9": true
-  }
-}
+{}