private void liftSparql11Subquery(
final AST2BOpContext context, final StaticAnalysis sa, final SubqueryRoot subqueryRoot) {
final IGroupNode<?> parent = subqueryRoot.getParent();
final String newName = "-subSelect-" + context.nextId();
final NamedSubqueryInclude include = new NamedSubqueryInclude(newName);
/**
* Set query hints from the parent join group.
*
* @see <a href="http://sourceforge.net/apps/trac/bigdata/ticket/791" > Clean up query hints
* </a>
*/
include.setQueryHints((Properties) parent.getProperty(ASTBase.Annotations.QUERY_HINTS));
/**
* Copy across attached join filters.
*
* @see <a href="https://sourceforge.net/apps/trac/bigdata/ticket/796" >Filter assigned to
* sub-query by query generator is dropped from evaluation</a>
*/
include.setAttachedJoinFilters(subqueryRoot.getAttachedJoinFilters());
/*
* Note: A SubqueryRoot normally starts out as the sole child of a
* JoinGroupNode. However, other rewrites may have written out that
* JoinGroupNode and it does not appear to be present for an ASK
* subquery.
*
* Therefore, when the parent of the SubqueryRoot is a JoinGroupNode
* having the SubqueryRoot as its only child, we use the parent's parent
* in order to replace the JoinGroupNode when we lift out the
* SubqueryRoot. Otherwise we use the parent since there is no wrapping
* JoinGroupNode (or if there is, it has some other stuff in there as
* well).
*
* BLZG-1542 -> there is an additional thing we need to take care of:
* whenever the parent node is an OPTIONAL or MINUS, we
* must not remove it, otherwise we would just "drop" an
* OPTIONAL or MINUS, thus changing the query's semantics
*
*/
if ((parent instanceof JoinGroupNode)
&& !((JoinGroupNode) parent).isOptional()
&& !((JoinGroupNode) parent).isMinus()
&& ((BOp) parent).arity() == 1
&& parent.getParent() != null
&& !((IGroupNode<?>) parent.getParent() instanceof UnionNode)) {
final IGroupNode<IGroupMemberNode> pp = parent.getParent();
// Replace the sub-select with the include.
if (((ASTBase) pp).replaceWith((BOp) parent, include) == 0) throw new AssertionError();
} else {
// Replace the sub-select with the include.
if (((ASTBase) parent).replaceWith((BOp) subqueryRoot, include) == 0)
throw new AssertionError();
}
final NamedSubqueryRoot nsr = new NamedSubqueryRoot(subqueryRoot.getQueryType(), newName);
/**
* Copy across query hints from the original subquery.
*
* @see <a href="http://sourceforge.net/apps/trac/bigdata/ticket/791" > Clean up query hints
* </a>
*/
nsr.setQueryHints(subqueryRoot.getQueryHints());
nsr.setConstruct(subqueryRoot.getConstruct());
nsr.setGroupBy(subqueryRoot.getGroupBy());
nsr.setHaving(subqueryRoot.getHaving());
nsr.setOrderBy(subqueryRoot.getOrderBy());
nsr.setProjection(subqueryRoot.getProjection());
nsr.setSlice(subqueryRoot.getSlice());
nsr.setWhereClause(subqueryRoot.getWhereClause());
nsr.setBindingsClause(subqueryRoot.getBindingsClause());
sa.getQueryRoot().getNamedSubqueriesNotNull().add(nsr);
}
/** Apply all optimizations. */
private void liftSubqueries(
final AST2BOpContext context,
final StaticAnalysis sa,
final GraphPatternGroup<IGroupMemberNode> group) {
final int arity = group.arity();
for (int i = 0; i < arity; i++) {
final BOp child = (BOp) group.get(i);
if (child instanceof GraphPatternGroup<?>) {
/*
* Note: Do recursion *before* we do the rewrite so we will
* rewrite Sub-Sub-Selects.
*
* FIXME Unit test for sub-sub-select optimization.
*/
liftSubqueries(context, sa, ((GraphPatternGroup<IGroupMemberNode>) child));
} else if (child instanceof SubqueryRoot) {
// Recursion into subqueries.
final SubqueryRoot subqueryRoot = (SubqueryRoot) child;
liftSubqueries(context, sa, subqueryRoot.getWhereClause());
} else if (child instanceof ServiceNode) {
// Do not rewrite things inside of a SERVICE node.
continue;
}
if (!(child instanceof SubqueryRoot)) {
continue;
}
final SubqueryRoot subqueryRoot = (SubqueryRoot) child;
if (subqueryRoot.getQueryType() == QueryType.ASK) {
/*
* FIXME Look at what would be involved in lifting an ASK
* sub-query. There are going to be at least two cases. If there
* is no join variable, then we always want to lift the ASK
* sub-query as it is completely independent of the parent
* group. If there is a join variable, then we need to project
* solutions which include the join variables from the subquery
* and the "ASK". At that point we can hash join against the
* projected solutions and the ASK succeeds if the hash join
* succeeds. [Add unit tests for this too.]
*/
continue;
}
if (subqueryRoot.hasSlice()) {
/*
* Lift out SPARQL 1.1 subqueries which use LIMIT and/or OFFSET.
*
* The SliceOp in the subquery will cause the IRunningQuery in
* which it appears to be interrupted. Therefore, when a SLICE
* is required for a subquery we need to lift it out to run it
* as a named subquery.
*
* TODO There may well be other cases that we have to handle
* with as-bound evaluation of a Subquery with a LIMIT/OFFSET.
* If so, then the subquery will have to be run using the
* SubqueryOp.
*/
liftSparql11Subquery(context, sa, subqueryRoot);
continue;
}
if (subqueryRoot.hasSlice() && subqueryRoot.getOrderBy() != null) {
/*
* Lift out SPARQL 1.1 subqueries which use both LIMIT and ORDER
* BY. Due to the interaction of the LIMIT and ORDER BY clause,
* these subqueries MUST be run first since they can produce
* different results if they are run "as-bound".
*/
liftSparql11Subquery(context, sa, subqueryRoot);
continue;
}
if (StaticAnalysis.isAggregate(subqueryRoot)) {
/*
* Lift out SPARQL 1.1 subqueries which use {@link IAggregate}s.
* This typically provides more efficient evaluation than
* repeated as-bound evaluation of the sub-select. It also
* prevents inappropriate sharing of the internal state of the
* {@link IAggregate} functions.
*/
liftSparql11Subquery(context, sa, subqueryRoot);
continue;
}
if (subqueryRoot.isRunOnce()) {
/*
* Lift out SPARQL 1.1 subqueries for which the RUN_ONCE
* annotation was specified.
*/
liftSparql11Subquery(context, sa, subqueryRoot);
continue;
}
/*
* FIXME We can not correctly predict the join variables at this
* time because that depends on the actual evaluation order. This
* has been commented out for now because it will otherwise cause
* all sub-selects to be lifted out.
*/
if (false) {
final Set<IVariable<?>> joinVars =
sa.getJoinVars(subqueryRoot, new LinkedHashSet<IVariable<?>>());
if (joinVars.isEmpty()) {
/*
* Lift out SPARQL 1.1 subqueries for which the RUN_ONCE
* annotation was specified.
*/
liftSparql11Subquery(context, sa, subqueryRoot);
continue;
}
}
}
}
