Treat INTERVAL as keyword in MySQL, TiDB and SingleStoreDB

src/languages/mariadb/likeMariaDb.ts

@@ -9,6 +9,10 @@ export function postProcess(tokens: Token[]) {
       // This is SET datatype, not SET statement
       return { ...token, type: TokenType.RESERVED_FUNCTION_NAME };
     }
+    if (isToken.INTERVAL(token) && nextToken.text === '(') {
+      // This is INTERVAL() function, not INTERVAL expression
+      return { ...token, type: TokenType.RESERVED_FUNCTION_NAME };
+    }
     const prevToken = tokens[i - 1] || EOF_TOKEN;
     if (isToken.VALUES(token) && prevToken.text === '=') {
       // This is VALUES() function, not VALUES clause

src/languages/mysql/mysql.functions.ts

@@ -131,7 +131,6 @@ export const functions: string[] = [
   'INTERNAL_MAX_DATA_LENGTH',
   'INTERNAL_TABLE_ROWS',
   'INTERNAL_UPDATE_TIME',
-  'INTERVAL',
   'IS',
   'IS_FREE_LOCK',
   'IS_IPV4',

src/languages/singlestoredb/singlestoredb.functions.ts

@@ -132,7 +132,6 @@ export const functions: string[] = [
   'INITCAP',
   'INSERT',
   'INSTR',
-  'INTERVAL',
   'IS',
   'IS NULL',
   'JSON_AGG',

src/languages/tidb/tidb.functions.ts

@@ -116,7 +116,6 @@ export const functions: string[] = [
   'INSERT_FUNC',
   'INSTR',
   'INTDIV',
-  'INTERVAL',
   'IS_FREE_LOCK',
   'IS_IPV4',
   'IS_IPV4_COMPAT',

src/lexer/token.ts

@@ -80,6 +80,7 @@ export const testToken =
 export const isToken = {
   ARRAY: testToken({ text: 'ARRAY', type: TokenType.RESERVED_DATA_TYPE }),
   BY: testToken({ text: 'BY', type: TokenType.RESERVED_KEYWORD }),
+  INTERVAL: testToken({ text: 'INTERVAL', type: TokenType.RESERVED_KEYWORD }),
   SET: testToken({ text: 'SET', type: TokenType.RESERVED_CLAUSE }),
   STRUCT: testToken({ text: 'STRUCT', type: TokenType.RESERVED_DATA_TYPE }),
   WINDOW: testToken({ text: 'WINDOW', type: TokenType.RESERVED_CLAUSE }),

test/behavesLikeMariaDbFormatter.ts

@@ -191,4 +191,19 @@ export default function behavesLikeMariaDbFormatter(format: FormatFn) {
       GRANT ALL ON *.* TO user2;
     `);
   });
+
+  // Issue #985
+  it('treats INTERVAL as keyword and INTERVAL() as function', () => {
+    expect(
+      format(`select now() - interval 30 day, date_sub(d, interval 1 hour), interval(5, 1, 10);`, {
+        keywordCase: 'upper',
+        functionCase: 'lower',
+      })
+    ).toBe(dedent`
+      SELECT
+        now() - INTERVAL 30 day,
+        date_sub(d, INTERVAL 1 hour),
+        interval(5, 1, 10);
+    `);
+  });
 }