PreparedStatements can take longer to execute than Statements. There seem to be
two problems with searchClauseTransitiveClosure method in PredicateList.java
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Key: DERBY-808
URL: http://issues.apache.org/jira/browse/DERBY-808
Project: Derby
Type: Bug
Components: SQL
Versions: 10.2.0.0, 10.1.2.0
Environment: generic
Reporter: Satheesh Bandaram
Fix For: 10.2.0.0, 10.1.3.0
PreparedStatements could take much longer than Statements because of incorrect
search clause transitive closure optimization. For the customer case I
investigated this problem, Statement would complete in about 13 seconds, where
as equivalent PreparedStatement ran "forever". (stoped it after hours)
I think there are two (minor) issues with
PredicateList.searchClauseTransitiveClosure method. This method tries to add
new search clauses based on equality join between tables involved. The issues
are:
1) Current code only looks for ConstantNodes on the right side of
searchClauses. This would miss ParameterNodes, so Derby might miss search
clause transitive closure optimizations for PreparedStatements.
2) Minor coding error:
if (left instanceof ColumnReference && right instanceof ConstantNode)
{
searchClauses.addElement(predicate);
}
else if (right instanceof ConstantNode && left instanceof ColumnReference)
{
// put the ColumnReference on the left to simplify things
bcon.swapOperands();
searchClauses.addElement(predicate);
}
The second part of the check is incorrect. It should instead be like:
else if (left instanceof ConstantNode && right instanceof ColumnReference)
and while handling ParameterNodes.
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