/**
* The redundant column is eliminated and the column order is correct according to standard SQL:
*
* <p>First, coalesced common columns of the two joined tables, in the order in which they occur
* in the first table.
*
* <p>Second, columns unique to the first table, in order in which they occur in that table.
*
* <p>Third, columns unique to the second table, in order in which they occur in that table.
*/
private Collection<ExpressionNode> buildProjection(
final SchemaContext sc, final Map<TableInstance, Set<ColumnKey>> tablesAndJoinColumns) {
final ListSetMap<ColumnKey, ExpressionNode> projection =
new ListSetMap<ColumnKey, ExpressionNode>();
/*
* We need to coalesce the join columns by their unqualified names.
* Build a lookup map.
*/
final Map<ColumnKey, Set<ColumnInstance>> toCoalesceName =
new TreeMap<ColumnKey, Set<ColumnInstance>>(
new Comparator<ColumnKey>() {
@Override
public int compare(ColumnKey c1, ColumnKey c2) {
final String n1 = getColumnName(c1).get();
final String n2 = getColumnName(c2).get();
return n1.compareTo(n2);
}
});
/*
* Here we the projection. Join columns are inserted in order in which
* they occur in the first table and coalesced by name in set
* containers.
*/
for (final Map.Entry<TableInstance, Set<ColumnKey>> te : tablesAndJoinColumns.entrySet()) {
final Set<ColumnKey> entryJoinColumns = te.getValue();
for (final ColumnKey ck : entryJoinColumns) {
final ColumnInstance ci = ck.toInstance();
if (!toCoalesceName.containsKey(ck)) {
projection.put(ck, ci);
final Set<ColumnInstance> coalescedColumns = new HashSet<ColumnInstance>();
coalescedColumns.add(ci);
toCoalesceName.put(ck, coalescedColumns);
} else {
toCoalesceName.get(ck).add(ci);
}
}
addColumns(sc, projection, te.getKey(), entryJoinColumns);
}
/*
* We already have the right projection.
*/
if (toCoalesceName.isEmpty()) {
return projection.values();
}
/*
* It turns out that in case of multi-join statements MySQL also sorts
* adjacent join columns by the number of coalesced columns (by the
* frequency with which they appear in the USING clauses).
*
* i.e.
* "SELECT * FROM pe251C c RIGHT JOIN pe251D d USING (id1,id2,id3) LEFT OUTER JOIN pe251E e USING (id1,id3) ORDER BY c.id1;"
*
* Although the first-table order would be (id2, id1, id3):
* "COALESCE(id2, id2), COALESCE(id1, id1, id1), COALESCE(id3, id3, id3)"
*
* MySQL sorts the columns as (id1, id3, id2):
* "COALESCE(id1, id1, id1), COALESCE(id3, id3, id3), COALESCE(id2, id2)"
*
* Sort the adjacent coalesced column sets by their size using a stable
* algorithm.
*/
final Map<ColumnKey, Set<ColumnInstance>> toCoalesceByEntry =
new HashMap<ColumnKey, Set<ColumnInstance>>(toCoalesceName);
final int endIndex = projection.size();
for (int i = 0; i < endIndex; ++i) {
final ColumnKey ik = projection.getEntryAt(i).getKey();
if (toCoalesceByEntry.containsKey(ik)) {
int j = i;
while (j > 0) {
final ColumnKey jk1 = projection.getEntryAt(j).getKey();
final ColumnKey jk2 = projection.getEntryAt(j - 1).getKey();
if (toCoalesceByEntry.containsKey(jk1) && toCoalesceByEntry.containsKey(jk2)) {
final Set<ColumnInstance> jv1 = toCoalesceByEntry.get(jk1);
final Set<ColumnInstance> jv2 = toCoalesceByEntry.get(jk2);
if (jv1.size() > jv2.size()) {
projection.swap(jk1, jk2);
} else {
break;
}
} else {
break;
}
--j;
}
}
}
/*
* Finally, convert the coalesced column sets into COALESCE() function
* calls.
*/
for (final Map.Entry<ColumnKey, Set<ColumnInstance>> coalesceEntry :
toCoalesceName.entrySet()) {
final ColumnKey key = coalesceEntry.getKey();
final FunctionCall coalesce =
new FunctionCall(
FunctionName.makeCoalesce(), new ArrayList<ExpressionNode>(coalesceEntry.getValue()));
final ExpressionAlias coalesceAlias =
new ExpressionAlias(coalesce, new NameAlias(getColumnName(key)), false);
projection.put(key, coalesceAlias);
}
return projection.values();
}
public static RedistFeatureStep buildLookupJoinRedist(
PlannerContext pc,
RedistFeatureStep lookupTable,
List<ExpressionNode> lookupJoinColumns,
PEStorageGroup targetGroup,
JoinEntry origEntry,
List<ExpressionNode> origJoinColumns,
PartitionEntry nonLookupSide)
throws PEException {
// we will modify the existing non lookup side projecting feature step, and add the lookup table
// as a requirement to it.
ProjectingFeatureStep nonLookupStep = (ProjectingFeatureStep) nonLookupSide.getStep(null);
nonLookupSide.maybeForceDoublePrecision(nonLookupStep);
SelectStatement lookupSelect = lookupTable.getTargetTempTable().buildSelect(pc.getContext());
SelectStatement nonLookupSelect = (SelectStatement) nonLookupStep.getPlannedStatement();
SelectStatement actualJoinStatement =
DMLStatementUtils.compose(pc.getContext(), nonLookupSelect, lookupSelect);
List<ExpressionNode> ands =
ExpressionUtils.decomposeAndClause(actualJoinStatement.getWhereClause());
// instead of building the join spec directly, map forward the original join condition from the
// joined table if it's available
IndexCollector ic = new IndexCollector();
if (origEntry.getJoin().getJoin() != null) {
FunctionCall mapped =
(FunctionCall)
actualJoinStatement
.getMapper()
.copyForward(origEntry.getJoin().getJoin().getJoinOn());
ands.add(mapped);
ListSet<ColumnInstance> cols = ColumnInstanceCollector.getColumnInstances(mapped);
for (ColumnInstance ci : cols) ic.addColumnInstance(ci);
} else {
Map<RewriteKey, ExpressionNode> projEntries = null;
for (int i = 0; i < origJoinColumns.size(); i++) {
ColumnKey mck =
actualJoinStatement.getMapper().mapExpressionToColumn(origJoinColumns.get(i));
ColumnKey muck =
actualJoinStatement.getMapper().mapExpressionToColumn(lookupJoinColumns.get(i));
ExpressionNode mc = null;
ExpressionNode muc = null;
if (mck == null || muck == null) {
if (projEntries == null) {
projEntries = new HashMap<RewriteKey, ExpressionNode>();
for (ExpressionNode en : actualJoinStatement.getProjectionEdge()) {
ExpressionNode actual = ExpressionUtils.getTarget(en);
if (actual instanceof ColumnInstance) {
projEntries.put(((ColumnInstance) actual).getColumnKey(), actual);
} else {
projEntries.put(new ExpressionKey(actual), actual);
}
}
}
if (mck == null)
mc =
(ExpressionNode)
projEntries.get(new ExpressionKey(origJoinColumns.get(i))).copy(null);
if (muck == null)
mc =
(ExpressionNode)
projEntries.get(new ExpressionKey(lookupJoinColumns.get(i))).copy(null);
}
if (mc == null) mc = mck.toInstance();
if (muc == null) muc = muck.toInstance();
if (mc instanceof ColumnInstance) ic.addColumnInstance((ColumnInstance) mc);
if (muc instanceof ColumnInstance) ic.addColumnInstance((ColumnInstance) muc);
FunctionCall eq = new FunctionCall(FunctionName.makeEquals(), mc, muc);
ands.add(eq);
}
}
ic.setIndexes(origEntry.getSchemaContext());
TempTable lookupEntryTarget = lookupTable.getTargetTempTable();
// everything from the lhs that's in the projection should be cleared - it's invisible
// note that we do it after building the where clause so that the original join condition can be
// mapped
for (Iterator<ExpressionNode> iter = actualJoinStatement.getProjectionEdge().iterator();
iter.hasNext(); ) {
ExpressionNode en = iter.next();
ExpressionNode targ = ExpressionUtils.getTarget(en);
if (targ instanceof ColumnInstance) {
ColumnInstance ci = (ColumnInstance) targ;
if (ci.getTableInstance().getAbstractTable() == lookupEntryTarget) iter.remove();
}
}
actualJoinStatement.setWhereClause(ExpressionUtils.safeBuildAnd(ands));
actualJoinStatement.normalize(origEntry.getSchemaContext());
// build a new projecting feature step
ProjectingFeatureStep lookupJoinStep =
DefaultFeatureStepBuilder.INSTANCE.buildProjectingStep(
origEntry.getPlannerContext(),
origEntry.getFeaturePlanner(),
actualJoinStatement,
new ExecutionCost(false, false, null, -1),
nonLookupStep.getSourceGroup(),
actualJoinStatement.getDatabase(origEntry.getSchemaContext()),
nonLookupStep.getDistributionVector(),
null,
DMLExplainReason.LOOKUP_JOIN.makeRecord());
// arrange for the children of the nonlookup side to become my children
// and add the lookup table step as well
lookupJoinStep.getSelfChildren().addAll(nonLookupStep.getAllChildren());
lookupJoinStep.getSelfChildren().add(lookupTable);
// children must be sequential - no need to modify here
List<Integer> mappedRedistOn =
nonLookupSide.mapDistributedOn(origJoinColumns, actualJoinStatement);
// now remove the lookup table from the mapper - have to do this pretty late - at this point
// the query won't be manipulated any more
actualJoinStatement.getMapper().remove(lookupEntryTarget);
RedistFeatureStep out =
lookupJoinStep.redist(
origEntry.getPlannerContext(),
origEntry.getFeaturePlanner(),
new TempTableCreateOptions(Model.STATIC, targetGroup)
.distributeOn(mappedRedistOn)
.withRowCount(origEntry.getScore().getRowCount()),
null,
DMLExplainReason.LOOKUP_JOIN.makeRecord());
return out;
}
private static UnqualifiedName getColumnName(final ColumnKey ck) {
return ck.getColumn().getName().getUnqualified();
}
