hsqldb Oracle mode select for update NOWAIT

问题:

It seems NOWAIT is not supported by HSQLDB in Oracle syntax.

HSQLDB version: 2.3.3

with

SET DATABASE SQL SYNTAX ORA TRUE;

Exception produced on the SQL

select a, b, c from sometable where id=1 for update NOWAIT

The exception

Caused by: org.hsqldb.HsqlException: unexpected token: NOWAIT
at org.hsqldb.error.Error.parseError(Unknown Source)
at org.hsqldb.ParserBase.unexpectedToken(Unknown Source)
at org.hsqldb.ParserCommand.compileStatement(Unknown Source)
at org.hsqldb.Session.compileStatement(Unknown Source)
at org.hsqldb.StatementManager.compile(Unknown Source)
at org.hsqldb.Session.execute(Unknown Source)

1. Does anyone know if HSQLDB does not supports this ?
2. Any ideas how to avoid this exception without modifying the original SQL. I can ignore the NOWAIT functionality in my unit tests but just cant modify the SQL. Additional info: we use spring-jbdc and JdbcTemplate and thinking about intercepting this to replace sqls with NOWAIT as an hack in the JUnit test setup.

回答1:

Found answer to my own question finally after digging hsqldb source code on sourceforge.

Version 2.3.3 of HSQLDB does NOT support NOWAIT.

I have asked this question in their Discussion Forum and raised the issue however its not like GitHub where you can create an issue so no formal Issue/Request opened.

I am getting along with a bad hack for now modifying HSQLDB code myself org.hsqldb.ParserDQL class to just ignore the NOWAIT in the select-for-update SQL.

If anyone has better answer I will accept their answer.

UPDATE: (Aug-24-2015)

Received confirmation from HSQLDB forum that NOWAIT will be ignored. Meanwhile I am posting the code snippet to ignore NOWAIT that I received from the HSQLDB sourceforge forum. You may want to wait for the next version of HSQLDB than adding this to your code base (as a hack).

 if (Tokens.T_NOWAIT.equals(token.tokenString)) {
        read();
 }

UPDATED to show the full context as to where to add the above snippet in the ParserDQL.java

    /**
 * Retrieves a SELECT or other query expression Statement from this parse context.
 */
StatementQuery compileCursorSpecification(RangeGroup[] rangeGroups,
        int props, boolean isRoutine) {

    OrderedHashSet  colNames        = null;
    QueryExpression queryExpression = XreadQueryExpression();

    if (token.tokenType == Tokens.FOR) {
        read();

        if (token.tokenType == Tokens.READ
                || token.tokenType == Tokens.FETCH) {
            read();
            readThis(Tokens.ONLY);

            props = ResultProperties.addUpdatable(props, false);
        } else {
            readThis(Tokens.UPDATE);

            props = ResultProperties.addUpdatable(props, true);

            if (token.tokenType == Tokens.OF) {
                readThis(Tokens.OF);

                colNames = new OrderedHashSet();

                readColumnNameList(colNames, null, false);
            }
            if (Tokens.T_NOWAIT.equalsIgnoreCase(token.tokenString)) {
                readIfThis(Tokens.X_IDENTIFIER);
            }
        }
    }