Details
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Bug
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Status: Closed
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Major
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Resolution: Fixed
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None
Description
After java.sql.Statement.getMoreResults() has returned false, the JDBC spec says that Statement.getUpdateCount() should return -1. This value indicates to the client that there are no additional result sets available. (Calcite currently supports at most one result set per SQL statement, and so there are never additional result sets available.)
Therefore the correct behavior for Avatica would be for the implementation of getMoreResults to reset updateCount.
Background
Some databases, such as Oracle Database, allow stored procedures to return multiple result sets. The JDBC API provides Statement.getMoreResults() for users to check if the statement has more than one result set and to retrieve the next result set. Calcite does not support this feature and only returns zero or one result set. The problem is that Calcite sometimes returns the wrong value for Statement.getUpdateCount() and indicates that additional results are available.
The JavaDoc for java.sql.Statement#getMoreResults(int) says there are no more results when the following is true:
// stmt is a Statement object ((stmt.getMoreResults(current) == false) && (stmt.getUpdateCount() == -1))
In AvaticaStatement, getMoreResults(int) always returns false to indicate there are no more ResultSet objects, but does not reset the updateCount which can indicate that there was an additional result (but that's not true). Since the JavaDoc states that clients should call both getMoreResults and getUpdateCount to determine if there are more results, any client that has the above Java code in a while loop would never reach an exit condition resulting in an infinite loop.
Steps to reproduce:
- Execute an INSERT query by calling Statement#execute(String). Verify that the return value is false indicating it is an update count.
- Call Statement#getMoreResults(). Verify that the return value is false indicating it is an update count or there are no more results.
- Call Statement#getUpdateCount().
Expected results:
The call to getUpdateCount() returns -1 indicating there are no more results.
Actual results:
The call to getUpdateCount() returns the update count for the INSERT query, which should only have one result.
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