DatabaseMetaData.getTables() etc. not working

[TimVermeiren]

When I tried the method DatabaseMetaData.getTables() (or getProcedures()), I always get back empty TABLE_NAME-columns (or PROCEDURE_NAME-columns).

When I manually did the underlying query:

SELECT CASE WHEN TABLE_CATALOG='' THEN NULL ELSE TABLE_CATALOG END AS TABLE_CAT, CASE WHEN TABLE_SCHEMA='' THEN NULL ELSE TABLE_SCHEMA END AS TABLE_SCHEM, TABLE_NAME, 'TABLE' AS TABLE_TYPE, NULL AS REMARKS, NULL AS TYPE_CAT, NULL AS TYPE_SCHEM, NULL AS TYPE_NAME, NULL AS SELF_REFERENCING_COL_NAME, NULL AS REF_GENERATION
FROM INFORMATION_SCHEMA.TABLES AS T
WHERE 1=1 

I've got

TABLE_CAT	TABLE_CAT	TABLE_SCHEM	TABLE_SCHEM	REMARKS	TABLE_TYPE	REMARKS	TYPE_CAT	TYPE_SCHEM	TYPE_NAME
null	null	tableName1	TABLE
null	null	tableName2	TABLE

When I changed the usages of CASE WHEN into COALESCE() it was working and gave the expected result:
SELECT COALESCE(TABLE_CATALOG, '') AS TABLE_CAT, COALESCE(TABLE_SCHEMA, '') AS TABLE_SCHEM, TABLE_NAME, 'TABLE' AS TABLE_TYPE, NULL AS REMARKS, NULL AS TYPE_CAT, NULL AS TYPE_SCHEM, NULL AS TYPE_NAME, NULL AS SELF_REFERENCING_COL_NAME, NULL AS REF_GENERATION FROM INFORMATION_SCHEMA.TABLES WHERE 1=1

TABLE_CAT	TABLE_SCHEM	TABLE_NAME	TABLE_TYPE	REMARKS	TYPE_CAT	TYPE_SCHEM	TYPE_NAME	SELF_REFERENCING_COL_NAME	REF_GENERATION
''	''	tableName1	TABLE
''	''	tableName2	TABLE

I don't have the time to file a proper pull request, but if someone could please change the constant
nl.topicus.jdbc.CloudSpannerDatabaseMetaDataConstants#SELECT_TABLES_COLUMNS
into

 public static final String SELECT_TABLES_COLUMNS =
      "SELECT COALESCE(TABLE_CATALOG, '') AS TABLE_CAT, COALESCE(TABLE_SCHEMA, '') AS TABLE_SCHEM, TABLE_NAME, 'TABLE' AS TABLE_TYPE, NULL AS REMARKS, NULL AS TYPE_CAT, NULL AS TYPE_SCHEM, NULL AS TYPE_NAME, NULL AS SELF_REFERENCING_COL_NAME, NULL AS REF_GENERATION ";

Thanks alot.