Handle USE DATABASE syntax and improve clientError detection

- Skip optional DATABASE keyword in USE statements (USE DATABASE d1 == USE d1)
- Only skip DATABASE if followed by an identifier (not semicolon/EOF)
- Track clientError annotations in splitStatements for proper handling
- Handle clientError for statements with no explain file (runtime errors)

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

Author: kyleconroy

parser/parser.go

@@ -6270,6 +6270,13 @@ func (p *Parser) parseUse() *ast.UseQuery {
 
 	p.nextToken() // skip USE
 
+	// Skip optional DATABASE keyword (USE DATABASE dbname is equivalent to USE dbname)
+	// But only if DATABASE is followed by another identifier/keyword (not semicolon or EOF)
+	// e.g., "USE DATABASE d1" vs "USE database" where database is the db name
+	if p.currentIs(token.DATABASE) && !p.peekIs(token.SEMICOLON) && !p.peekIs(token.EOF) {
+		p.nextToken()
+	}
+
 	// Database name can be an identifier or a keyword like DEFAULT (can also start with number)
 	use.Database = p.parseIdentifierName()
 

parser/parser_test.go

@@ -27,10 +27,17 @@ type testMetadata struct {
 	ParseError  bool            `json:"parse_error,omitempty"` // true if query is intentionally invalid SQL
 }
 
+// statementInfo holds a parsed statement and its metadata
+type statementInfo struct {
+	stmt          string
+	hasClientErr  bool
+}
+
 // splitStatements splits SQL content into individual statements.
-func splitStatements(content string) []string {
-	var statements []string
+func splitStatements(content string) []statementInfo {
+	var statements []statementInfo
 	var current strings.Builder
+	var currentHasClientErr bool
 
 	lines := strings.Split(content, "\n")
 	for _, line := range lines {
@@ -41,6 +48,12 @@ func splitStatements(content string) []string {
 			continue
 		}
 
+		// Check for clientError annotation before stripping comment
+		// Handles both "-- { clientError" and "--{clientError" formats
+		if strings.Contains(trimmed, "clientError") {
+			currentHasClientErr = true
+		}
+
 		// Remove inline comments (-- comment at end of line)
 		if idx := findCommentStart(trimmed); idx >= 0 {
 			trimmed = strings.TrimSpace(trimmed[:idx])
@@ -60,17 +73,18 @@ func splitStatements(content string) []string {
 			stmt := strings.TrimSpace(current.String())
 			// Skip empty statements (just semicolons or empty)
 			if stmt != "" && stmt != ";" {
-				statements = append(statements, stmt)
+				statements = append(statements, statementInfo{stmt: stmt, hasClientErr: currentHasClientErr})
 			}
 			current.Reset()
+			currentHasClientErr = false
 		}
 	}
 
 	// Handle statement without trailing semicolon
 	if current.Len() > 0 {
 		stmt := strings.TrimSpace(current.String())
 		if stmt != "" {
-			statements = append(statements, stmt)
+			statements = append(statements, statementInfo{stmt: stmt, hasClientErr: currentHasClientErr})
 		}
 	}
 
@@ -170,9 +184,11 @@ func TestParser(t *testing.T) {
 			}
 
 			// Test each statement as a subtest
-			for i, stmt := range statements {
+			for i, stmtInfo := range statements {
 				stmtIndex := i + 1
 				t.Run(fmt.Sprintf("stmt%d", stmtIndex), func(t *testing.T) {
+					stmt := stmtInfo.stmt
+
 					// Determine explain file path: explain.txt for first, explain_N.txt for N >= 2
 					var explainPath string
 					if stmtIndex == 1 {
@@ -181,15 +197,6 @@ func TestParser(t *testing.T) {
 						explainPath = filepath.Join(testDir, fmt.Sprintf("explain_%d.txt", stmtIndex))
 					}
 
-					// For statements beyond the first, skip if no explain file exists
-					// (these statements haven't been regenerated yet)
-					if stmtIndex > 1 {
-						if _, err := os.Stat(explainPath); os.IsNotExist(err) {
-							t.Skipf("No explain_%d.txt file (run regenerate-explain to generate)", stmtIndex)
-							return
-						}
-					}
-
 					// Skip statements marked in explain_todo (unless -check-explain is set)
 					stmtKey := fmt.Sprintf("stmt%d", stmtIndex)
 					isExplainTodo := metadata.ExplainTodo[stmtKey]
@@ -198,6 +205,41 @@ func TestParser(t *testing.T) {
 						return
 					}
 
+					// For statements beyond the first, check if explain file exists
+					explainFileExists := true
+					if stmtIndex > 1 {
+						if _, err := os.Stat(explainPath); os.IsNotExist(err) {
+							explainFileExists = false
+						}
+					}
+
+					// If no explain file and statement has clientError annotation, skip (no expected output for runtime errors)
+					if !explainFileExists && stmtInfo.hasClientErr {
+						// Remove from explain_todo if present
+						if isExplainTodo && *checkExplain {
+							delete(metadata.ExplainTodo, stmtKey)
+							if len(metadata.ExplainTodo) == 0 {
+								metadata.ExplainTodo = nil
+							}
+							updatedBytes, err := json.MarshalIndent(metadata, "", "  ")
+							if err != nil {
+								t.Errorf("Failed to marshal updated metadata: %v", err)
+							} else if err := os.WriteFile(metadataPath, append(updatedBytes, '\n'), 0644); err != nil {
+								t.Errorf("Failed to write updated metadata.json: %v", err)
+							} else {
+								t.Logf("EXPLAIN PASSES NOW (clientError skip, no explain file) - removed explain_todo[%s] from: %s", stmtKey, entry.Name())
+							}
+						}
+						t.Skipf("No explain_%d.txt file (clientError annotation - runtime error)", stmtIndex)
+						return
+					}
+
+					// For statements beyond the first without clientError, skip if no explain file exists
+					if !explainFileExists {
+						t.Skipf("No explain_%d.txt file (run regenerate-explain to generate)", stmtIndex)
+						return
+					}
+
 					// Create context with 1 second timeout
 					ctx, cancel := context.WithTimeout(context.Background(), 1*time.Second)
 					defer cancel()
@@ -242,9 +284,9 @@ func TestParser(t *testing.T) {
 						if strings.HasSuffix(expected, "\nOK") {
 							expected = strings.TrimSpace(expected[:len(expected)-3])
 						}
-						// Skip if expected is empty and statement has --{clientError annotation
+						// Skip if expected is empty and statement has clientError annotation
 						// (ClickHouse errors at runtime before producing EXPLAIN output)
-						if expected == "" && strings.Contains(stmt, "--{clientError") {
+						if expected == "" && stmtInfo.hasClientErr {
 							// Also remove from explain_todo if present (this case is now handled)
 							if isExplainTodo && *checkExplain {
 								delete(metadata.ExplainTodo, stmtKey)
@@ -260,7 +302,7 @@ func TestParser(t *testing.T) {
 									t.Logf("EXPLAIN PASSES NOW (clientError skip) - removed explain_todo[%s] from: %s", stmtKey, entry.Name())
 								}
 							}
-							t.Skipf("Skipping: empty expected output with --{clientError annotation")
+							t.Skipf("Skipping: empty expected output with clientError annotation")
 							return
 						}
 						actual := strings.TrimSpace(parser.Explain(stmts[0]))

parser/testdata/01292_create_user/metadata.json

@@ -1,5 +1 @@
-{
-  "explain_todo": {
-    "stmt239": true
-  }
-}
+{}

parser/testdata/03512_settings_max_block_size/metadata.json

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

parser/testdata/03532_use_database_syntax/metadata.json

@@ -1,5 +1 @@
-{
-  "explain_todo": {
-    "stmt5": true
-  }
-}
+{}