Implement pulling up rows to coordinator when aggregates cannot be pushed down. Enabled by default

src/backend/distributed/planner/extended_op_node_utils.c

@@ -42,7 +42,8 @@ static bool ShouldPullDistinctColumn(bool repartitionSubquery,
  * value should be used in a read-only manner.
  */
 ExtendedOpNodeProperties
-BuildExtendedOpNodeProperties(MultiExtendedOp *extendedOpNode)
+BuildExtendedOpNodeProperties(MultiExtendedOp *extendedOpNode, bool
+							  pullUpIntermediateRows)
 {
 	ExtendedOpNodeProperties extendedOpNodeProperties;
 
@@ -75,6 +76,7 @@ BuildExtendedOpNodeProperties(MultiExtendedOp *extendedOpNode)
 		hasNonPartitionColumnDistinctAgg;
 	extendedOpNodeProperties.pullDistinctColumns = pullDistinctColumns;
 	extendedOpNodeProperties.pushDownWindowFunctions = pushDownWindowFunctions;
+	extendedOpNodeProperties.pullUpIntermediateRows = pullUpIntermediateRows;
 
 	return extendedOpNodeProperties;
 }

src/backend/distributed/planner/multi_logical_optimizer.c

@@ -27,8 +27,10 @@
 #include "distributed/citus_nodes.h"
 #include "distributed/citus_ruleutils.h"
 #include "distributed/colocation_utils.h"
+#include "distributed/errormessage.h"
 #include "distributed/extended_op_node_utils.h"
 #include "distributed/function_utils.h"
+#include "distributed/listutils.h"
 #include "distributed/metadata_cache.h"
 #include "distributed/multi_logical_optimizer.h"
 #include "distributed/multi_logical_planner.h"
@@ -59,19 +61,19 @@
 /* Config variable managed via guc.c */
 int LimitClauseRowFetchCount = -1; /* number of rows to fetch from each task */
 double CountDistinctErrorRate = 0.0; /* precision of count(distinct) approximate */
-
+int CoordinatorAggregationStrategy = COORDINATOR_AGGREGATION_ROW_GATHER;
 
 typedef struct MasterAggregateWalkerContext
 {
+	const ExtendedOpNodeProperties *extendedOpNodeProperties;
 	AttrNumber columnId;
-	bool pullDistinctColumns;
 } MasterAggregateWalkerContext;
 
 typedef struct WorkerAggregateWalkerContext
 {
+	const ExtendedOpNodeProperties *extendedOpNodeProperties;
 	List *expressionList;
 	bool createGroupByClause;
-	bool pullDistinctColumns;
 } WorkerAggregateWalkerContext;
 
 
@@ -189,7 +191,8 @@ static void ParentSetNewChild(MultiNode *parentNode, MultiNode *oldChildNode,
 static void ApplyExtendedOpNodes(MultiExtendedOp *originalNode,
 								 MultiExtendedOp *masterNode,
 								 MultiExtendedOp *workerNode);
-static void TransformSubqueryNode(MultiTable *subqueryNode);
+static void TransformSubqueryNode(MultiTable *subqueryNode, bool
+								  requiresIntermediateRowPullUp);
 static MultiExtendedOp * MasterExtendedOpNode(MultiExtendedOp *originalOpNode,
 											  ExtendedOpNodeProperties *
 											  extendedOpNodeProperties);
@@ -267,12 +270,18 @@ static Const * MakeIntegerConst(int32 integerValue);
 static Const * MakeIntegerConstInt64(int64 integerValue);
 
 /* Local functions forward declarations for aggregate expression checks */
-static void ErrorIfContainsUnsupportedAggregate(MultiNode *logicalPlanNode);
-static void ErrorIfUnsupportedArrayAggregate(Aggref *arrayAggregateExpression);
-static void ErrorIfUnsupportedJsonAggregate(AggregateType type,
-											Aggref *aggregateExpression);
-static void ErrorIfUnsupportedAggregateDistinct(Aggref *aggregateExpression,
+static bool RequiresIntermediateRowPullUp(MultiNode *logicalPlanNode);
+static DeferredErrorMessage * DeferErrorIfContainsNonPushdownableAggregate(
 	MultiNode *logicalPlanNode);
+static DeferredErrorMessage * DeferErrorIfUnsupportedArrayAggregate(
+	Aggref *arrayAggregateExpression);
+static DeferredErrorMessage * DeferErrorIfUnsupportedJsonAggregate(AggregateType type,
+																   Aggref *
+																   aggregateExpression);
+static DeferredErrorMessage * DeferErrorIfUnsupportedAggregateDistinct(
+	Aggref *aggregateExpression,
+	MultiNode *
+	logicalPlanNode);
 static Var * AggregateDistinctColumn(Aggref *aggregateExpression);
 static bool TablePartitioningSupportsDistinct(List *tableNodeList,
 											  MultiExtendedOp *opNode,
@@ -315,16 +324,29 @@ MultiLogicalPlanOptimize(MultiTreeRoot *multiLogicalPlan)
 	ListCell *collectNodeCell = NULL;
 	ListCell *tableNodeCell = NULL;
 	MultiNode *logicalPlanNode = (MultiNode *) multiLogicalPlan;
-
+	bool requiresIntermediateRowPullUp = RequiresIntermediateRowPullUp(logicalPlanNode);
 	List *extendedOpNodeList = FindNodesOfType(logicalPlanNode, T_MultiExtendedOp);
 	MultiExtendedOp *extendedOpNode = (MultiExtendedOp *) linitial(extendedOpNodeList);
 	ExtendedOpNodeProperties extendedOpNodeProperties = BuildExtendedOpNodeProperties(
-		extendedOpNode);
+		extendedOpNode, requiresIntermediateRowPullUp);
 
-	if (!extendedOpNodeProperties.groupedByDisjointPartitionColumn)
+	if (!extendedOpNodeProperties.groupedByDisjointPartitionColumn &&
+		!extendedOpNodeProperties.pullUpIntermediateRows)
 	{
-		/* check that we can optimize aggregates in the plan */
-		ErrorIfContainsUnsupportedAggregate(logicalPlanNode);
+		DeferredErrorMessage *aggregatePushdownError =
+			DeferErrorIfContainsNonPushdownableAggregate(logicalPlanNode);
+
+		if (aggregatePushdownError != NULL)
+		{
+			if (CoordinatorAggregationStrategy == COORDINATOR_AGGREGATION_DISABLED)
+			{
+				RaiseDeferredError(aggregatePushdownError, ERROR);
+			}
+			else
+			{
+				extendedOpNodeProperties.pullUpIntermediateRows = true;
+			}
+		}
 	}
 
 	/*
@@ -382,7 +404,6 @@ MultiLogicalPlanOptimize(MultiTreeRoot *multiLogicalPlan)
 	 * clause list to the worker operator node. We then push the worker operator
 	 * node below the collect node.
 	 */
-
 	MultiExtendedOp *masterExtendedOpNode =
 		MasterExtendedOpNode(extendedOpNode, &extendedOpNodeProperties);
 	MultiExtendedOp *workerExtendedOpNode =
@@ -396,8 +417,23 @@ MultiLogicalPlanOptimize(MultiTreeRoot *multiLogicalPlan)
 		MultiTable *tableNode = (MultiTable *) lfirst(tableNodeCell);
 		if (tableNode->relationId == SUBQUERY_RELATION_ID)
 		{
-			ErrorIfContainsUnsupportedAggregate((MultiNode *) tableNode);
-			TransformSubqueryNode(tableNode);
+			DeferredErrorMessage *error =
+				DeferErrorIfContainsNonPushdownableAggregate((MultiNode *) tableNode);
+			bool subqueryRequiresIntermediateRowPullUp = false;
+
+			if (error != NULL)
+			{
+				if (CoordinatorAggregationStrategy == COORDINATOR_AGGREGATION_DISABLED)
+				{
+					RaiseDeferredError(error, ERROR);
+				}
+				else
+				{
+					subqueryRequiresIntermediateRowPullUp = true;
+				}
+			}
+
+			TransformSubqueryNode(tableNode, subqueryRequiresIntermediateRowPullUp);
 		}
 	}
 
@@ -1281,15 +1317,22 @@ ApplyExtendedOpNodes(MultiExtendedOp *originalNode, MultiExtendedOp *masterNode,
  * operator node.
  */
 static void
-TransformSubqueryNode(MultiTable *subqueryNode)
+TransformSubqueryNode(MultiTable *subqueryNode, bool requiresIntermediateRowPullUp)
 {
+	if (CoordinatorAggregationStrategy != COORDINATOR_AGGREGATION_DISABLED &&
+		RequiresIntermediateRowPullUp((MultiNode *) subqueryNode))
+	{
+		requiresIntermediateRowPullUp = true;
+	}
+
 	MultiExtendedOp *extendedOpNode =
 		(MultiExtendedOp *) ChildNode((MultiUnaryNode *) subqueryNode);
 	MultiNode *collectNode = ChildNode((MultiUnaryNode *) extendedOpNode);
 	MultiNode *collectChildNode = ChildNode((MultiUnaryNode *) collectNode);
 
 	ExtendedOpNodeProperties extendedOpNodeProperties =
-		BuildExtendedOpNodeProperties(extendedOpNode);
+		BuildExtendedOpNodeProperties(extendedOpNode, requiresIntermediateRowPullUp);
+
 	MultiExtendedOp *masterExtendedOpNode =
 		MasterExtendedOpNode(extendedOpNode, &extendedOpNodeProperties);
 	MultiExtendedOp *workerExtendedOpNode =
@@ -1369,8 +1412,8 @@ MasterExtendedOpNode(MultiExtendedOp *originalOpNode,
 	MasterAggregateWalkerContext *walkerContext = palloc0(
 		sizeof(MasterAggregateWalkerContext));
 
+	walkerContext->extendedOpNodeProperties = extendedOpNodeProperties;
 	walkerContext->columnId = 1;
-	walkerContext->pullDistinctColumns = extendedOpNodeProperties->pullDistinctColumns;
 
 	/* iterate over original target entries */
 	foreach(targetEntryCell, targetEntryList)
@@ -1509,16 +1552,62 @@ static Expr *
 MasterAggregateExpression(Aggref *originalAggregate,
 						  MasterAggregateWalkerContext *walkerContext)
 {
-	AggregateType aggregateType = GetAggregateType(originalAggregate);
-	Expr *newMasterExpression = NULL;
 	const uint32 masterTableId = 1;  /* one table on the master node */
 	const Index columnLevelsUp = 0;  /* normal column */
 	const AttrNumber argumentId = 1; /* our aggregates have single arguments */
+	AggregateType aggregateType = GetAggregateType(originalAggregate);
+	Expr *newMasterExpression = NULL;
 	AggClauseCosts aggregateCosts;
 
-	if (aggregateType == AGGREGATE_COUNT && originalAggregate->aggdistinct &&
+	if (walkerContext->extendedOpNodeProperties->pullUpIntermediateRows)
+	{
+		Aggref *aggregate = (Aggref *) copyObject(originalAggregate);
+
+		TargetEntry *targetEntry;
+		foreach_ptr(targetEntry, aggregate->args)
+		{
+			targetEntry->expr = (Expr *)
+								makeVar(masterTableId, walkerContext->columnId,
+										exprType((Node *) targetEntry->expr),
+										exprTypmod((Node *) targetEntry->expr),
+										exprCollation((Node *) targetEntry->expr),
+										columnLevelsUp);
+			walkerContext->columnId++;
+		}
+
+		aggregate->aggdirectargs = NIL;
+		Expr *directarg;
+		foreach_ptr(directarg, originalAggregate->aggdirectargs)
+		{
+			if (!IsA(directarg, Const) && !IsA(directarg, Param))
+			{
+				Var *var = makeVar(masterTableId, walkerContext->columnId,
+								   exprType((Node *) directarg),
+								   exprTypmod((Node *) directarg),
+								   exprCollation((Node *) directarg),
+								   columnLevelsUp);
+				aggregate->aggdirectargs = lappend(aggregate->aggdirectargs, var);
+				walkerContext->columnId++;
+			}
+			else
+			{
+				aggregate->aggdirectargs = lappend(aggregate->aggdirectargs, directarg);
+			}
+		}
+
+		if (aggregate->aggfilter)
+		{
+			aggregate->aggfilter = (Expr *)
+								   makeVar(masterTableId, walkerContext->columnId,
+										   BOOLOID, -1, InvalidOid, columnLevelsUp);
+			walkerContext->columnId++;
+		}
+
+		newMasterExpression = (Expr *) aggregate;
+	}
+	else if (aggregateType == AGGREGATE_COUNT && originalAggregate->aggdistinct &&
 			 CountDistinctErrorRate == DISABLE_DISTINCT_APPROXIMATION &&
-		walkerContext->pullDistinctColumns)
+			 walkerContext->extendedOpNodeProperties->pullDistinctColumns)
 	{
 		Aggref *aggregate = (Aggref *) copyObject(originalAggregate);
 		List *varList = pull_var_clause_default((Node *) aggregate);
@@ -1834,7 +1923,7 @@ MasterAggregateExpression(Aggref *originalAggregate,
 
 		newMasterExpression = (Expr *) unionAggregate;
 	}
-	else if (aggregateType == AGGREGATE_CUSTOM)
+	else if (aggregateType == AGGREGATE_CUSTOM_COMBINE)
 	{
 		HeapTuple aggTuple =
 			SearchSysCache1(AGGFNOID, ObjectIdGetDatum(originalAggregate->aggfnoid));
@@ -2102,8 +2191,17 @@ WorkerExtendedOpNode(MultiExtendedOp *originalOpNode,
 	/* targetProjectionNumber starts from 1 */
 	queryTargetList.targetProjectionNumber = 1;
 
-	/* worker query always include all the group by entries in the query */
+	/*
+	 * only push down grouping to worker query when pushing down aggregates
+	 */
+	if (extendedOpNodeProperties->pullUpIntermediateRows)
+	{
+		queryGroupClause.groupClauseList = NIL;
+	}
+	else
+	{
 		queryGroupClause.groupClauseList = copyObject(originalGroupClauseList);
+	}
 
 	/*
 	 * nextSortGroupRefIndex is used by group by, window and order by clauses.
@@ -2122,14 +2220,16 @@ WorkerExtendedOpNode(MultiExtendedOp *originalOpNode,
 									  &queryHavingQual, &queryTargetList,
 									  &queryGroupClause);
 
+	ProcessWindowFunctionsForWorkerQuery(originalWindowClause, originalTargetEntryList,
+										 &queryWindowClause, &queryTargetList);
+
+	if (!extendedOpNodeProperties->pullUpIntermediateRows)
+	{
 		ProcessDistinctClauseForWorkerQuery(originalDistinctClause, hasDistinctOn,
 											queryGroupClause.groupClauseList,
 											queryHasAggregates, &queryDistinctClause,
 											&distinctPreventsLimitPushdown);
 
-	ProcessWindowFunctionsForWorkerQuery(originalWindowClause, originalTargetEntryList,
-										 &queryWindowClause, &queryTargetList);
-
 		/*
 		 * Order by and limit clauses are relevant to each other, and processing
 		 * them together makes it handy for us.
@@ -2158,6 +2258,7 @@ WorkerExtendedOpNode(MultiExtendedOp *originalOpNode,
 											  &queryOrderByLimit,
 											  &queryTargetList);
 		}
+	}
 
 	/* finally, fill the extended op node with the data we gathered */
 	MultiExtendedOp *workerExtendedOpNode = CitusMakeNode(MultiExtendedOp);
@@ -2211,8 +2312,8 @@ ProcessTargetListForWorkerQuery(List *targetEntryList,
 	WorkerAggregateWalkerContext *workerAggContext =
 		palloc0(sizeof(WorkerAggregateWalkerContext));
 
+	workerAggContext->extendedOpNodeProperties = extendedOpNodeProperties;
 	workerAggContext->expressionList = NIL;
-	workerAggContext->pullDistinctColumns = extendedOpNodeProperties->pullDistinctColumns;
 
 	/* iterate over original target entries */
 	foreach(targetEntryCell, targetEntryList)
@@ -2274,8 +2375,6 @@ ProcessHavingClauseForWorkerQuery(Node *originalHavingQual,
 								  QueryTargetList *queryTargetList,
 								  QueryGroupClause *queryGroupClause)
 {
-	TargetEntry *targetEntry = NULL;
-
 	if (originalHavingQual == NULL)
 	{
 		return;
@@ -2291,13 +2390,14 @@ ProcessHavingClauseForWorkerQuery(Node *originalHavingQual,
 		 */
 		WorkerAggregateWalkerContext *workerAggContext = palloc0(
 			sizeof(WorkerAggregateWalkerContext));
+
+		workerAggContext->extendedOpNodeProperties = extendedOpNodeProperties;
 		workerAggContext->expressionList = NIL;
-		workerAggContext->pullDistinctColumns =
-			extendedOpNodeProperties->pullDistinctColumns;
 		workerAggContext->createGroupByClause = false;
 
 		WorkerAggregateWalker(originalHavingQual, workerAggContext);
 		List *newExpressionList = workerAggContext->expressionList;
+		TargetEntry *targetEntry = NULL;
 
 		ExpandWorkerTargetEntry(newExpressionList, targetEntry,
 								workerAggContext->createGroupByClause,
@@ -2348,7 +2448,7 @@ ProcessHavingClauseForWorkerQuery(Node *originalHavingQual,
  * and DISTINCT ON clauses to the worker queries.
  *
  * The function also sets distinctPreventsLimitPushdown. As the name reveals,
- * distinct could prevent pushwing down LIMIT clauses later in the planning.
+ * distinct could prevent pushing down LIMIT clauses later in the planning.
  * For the details, see the comments in the function.
  *
  *     inputs: distinctClause, hasDistinctOn, groupClauseList, queryHasAggregates
@@ -2362,14 +2462,14 @@ ProcessDistinctClauseForWorkerQuery(List *distinctClause, bool hasDistinctOn,
 									QueryDistinctClause *queryDistinctClause,
 									bool *distinctPreventsLimitPushdown)
 {
-	bool distinctClauseSupersetofGroupClause = false;
+	*distinctPreventsLimitPushdown = false;
 
 	if (distinctClause == NIL)
 	{
 		return;
 	}
 
-	*distinctPreventsLimitPushdown = false;
+	bool distinctClauseSupersetofGroupClause = false;
 
 	if (groupClauseList == NIL ||
 		IsGroupBySubsetOfDistinct(groupClauseList, distinctClause))
@@ -2412,13 +2512,13 @@ ProcessDistinctClauseForWorkerQuery(List *distinctClause, bool hasDistinctOn,
  * pushdown.
  *
  * TODO: Citus only supports pushing down window clauses as-is under certain circumstances.
- * And, at this point in the planning, we are guaraanted to process a window function
+ * And, at this point in the planning, we are guaranteed to process a window function
  * which is safe to pushdown as-is. It should also be possible to pull the relevant data
  * to the coordinator and apply the window clauses for the remaining cases.
  *
  * Note that even though Citus only pushes down the window functions, it may need to
  * modify the target list of the worker query when the window function refers to
- * an avg(). The reason is that any aggragate which is also referred by other
+ * an avg(). The reason is that any aggregate which is also referred by other
  * target entries would be mutated by Citus. Thus, we add a copy of the same aggragate
  * to the worker target list to make sure that the window function refers to the
  * non-mutated aggragate.
@@ -2465,8 +2565,8 @@ ProcessWindowFunctionsForWorkerQuery(List *windowClauseList,
 		 * Note that even Citus does push down the window clauses as-is, we may still need to
 		 * add the generated entries to the target list. The reason is that the same aggragates
 		 * might be referred from another target entry that is a bare aggragate (e.g., no window
-		 * functions), which would have been mutated. For instance, when an average aggragate
-		 * is mutated on the target list, the window function would refer to a sum aggragate,
+		 * functions), which would have been mutated. For instance, when an average aggregate
+		 * is mutated on the target list, the window function would refer to a sum aggregate,
 		 * which is obviously wrong.
 		 */
 		queryTargetList->targetEntryList = list_concat(queryTargetList->targetEntryList,
@@ -2614,7 +2714,7 @@ ExpandWorkerTargetEntry(List *expressionList, TargetEntry *originalTargetEntry,
 		TargetEntry *newTargetEntry =
 			GenerateWorkerTargetEntry(originalTargetEntry, newExpression,
 									  queryTargetList->targetProjectionNumber);
-		(queryTargetList->targetProjectionNumber)++;
+		queryTargetList->targetProjectionNumber++;
 		queryTargetList->targetEntryList =
 			lappend(queryTargetList->targetEntryList, newTargetEntry);
 
@@ -2682,7 +2782,7 @@ GenerateWorkerTargetEntry(TargetEntry *targetEntry, Expr *workerExpression,
 	 */
 	if (targetEntry)
 	{
-		newTargetEntry = copyObject(targetEntry);
+		newTargetEntry = flatCopyTargetEntry(targetEntry);
 	}
 	else
 	{
@@ -2699,7 +2799,7 @@ GenerateWorkerTargetEntry(TargetEntry *targetEntry, Expr *workerExpression,
 		newTargetEntry->resname = columnNameString->data;
 	}
 
-	/* we can generate a target entry without any expressions */
+	/* we can't generate a target entry without an expression */
 	Assert(workerExpression != NULL);
 
 	/* force resjunk to false as we may need this on the master */
@@ -2795,13 +2895,40 @@ static List *
 WorkerAggregateExpressionList(Aggref *originalAggregate,
 							  WorkerAggregateWalkerContext *walkerContext)
 {
-	AggregateType aggregateType = GetAggregateType(originalAggregate);
 	List *workerAggregateList = NIL;
+
+	if (walkerContext->extendedOpNodeProperties->pullUpIntermediateRows)
+	{
+		TargetEntry *targetEntry;
+		foreach_ptr(targetEntry, originalAggregate->args)
+		{
+			workerAggregateList = lappend(workerAggregateList, targetEntry->expr);
+		}
+
+		Expr *directarg;
+		foreach_ptr(directarg, originalAggregate->aggdirectargs)
+		{
+			if (!IsA(directarg, Const) && !IsA(directarg, Param))
+			{
+				workerAggregateList = lappend(workerAggregateList, directarg);
+			}
+		}
+
+		if (originalAggregate->aggfilter)
+		{
+			workerAggregateList = lappend(workerAggregateList,
+										  originalAggregate->aggfilter);
+		}
+
+		return workerAggregateList;
+	}
+
+	AggregateType aggregateType = GetAggregateType(originalAggregate);
 	AggClauseCosts aggregateCosts;
 
 	if (aggregateType == AGGREGATE_COUNT && originalAggregate->aggdistinct &&
 		CountDistinctErrorRate == DISABLE_DISTINCT_APPROXIMATION &&
-		walkerContext->pullDistinctColumns)
+		walkerContext->extendedOpNodeProperties->pullDistinctColumns)
 	{
 		Aggref *aggregate = (Aggref *) copyObject(originalAggregate);
 		List *columnList = pull_var_clause_default((Node *) aggregate);
@@ -2910,7 +3037,7 @@ WorkerAggregateExpressionList(Aggref *originalAggregate,
 		workerAggregateList = lappend(workerAggregateList, sumAggregate);
 		workerAggregateList = lappend(workerAggregateList, countAggregate);
 	}
-	else if (aggregateType == AGGREGATE_CUSTOM)
+	else if (aggregateType == AGGREGATE_CUSTOM_COMBINE)
 	{
 		HeapTuple aggTuple =
 			SearchSysCache1(AGGFNOID, ObjectIdGetDatum(originalAggregate->aggfnoid));
@@ -3019,10 +3146,17 @@ GetAggregateType(Aggref *aggregateExpression)
 
 	if (AggregateEnabledCustom(aggregateExpression))
 	{
-		return AGGREGATE_CUSTOM;
+		return AGGREGATE_CUSTOM_COMBINE;
 	}
 
+	if (CoordinatorAggregationStrategy == COORDINATOR_AGGREGATION_DISABLED)
+	{
 		ereport(ERROR, (errmsg("unsupported aggregate function %s", aggregateProcName)));
+	}
+	else
+	{
+		return AGGREGATE_CUSTOM_ROW_GATHER;
+	}
 }
 
 
@@ -3337,14 +3471,59 @@ MakeIntegerConstInt64(int64 integerValue)
 
 
 /*
- * ErrorIfContainsUnsupportedAggregate extracts aggregate expressions from the
- * logical plan, walks over them and uses helper functions to check if we can
- * transform these aggregate expressions and push them down to worker nodes.
- * These helper functions error out if we cannot transform the aggregates.
+ * RequiresIntermediateRowPullUp checks for if any aggregates cannot be pushed down.
  */
-static void
-ErrorIfContainsUnsupportedAggregate(MultiNode *logicalPlanNode)
+static bool
+RequiresIntermediateRowPullUp(MultiNode *logicalPlanNode)
 {
+	if (CoordinatorAggregationStrategy == COORDINATOR_AGGREGATION_DISABLED)
+	{
+		return false;
+	}
+
+	List *opNodeList = FindNodesOfType(logicalPlanNode, T_MultiExtendedOp);
+	MultiExtendedOp *extendedOpNode = (MultiExtendedOp *) linitial(opNodeList);
+
+	List *targetList = extendedOpNode->targetList;
+
+	/*
+	 * PVC_REJECT_PLACEHOLDERS is implicit if PVC_INCLUDE_PLACEHOLDERS isn't
+	 * specified.
+	 */
+	List *expressionList = pull_var_clause((Node *) targetList, PVC_INCLUDE_AGGREGATES |
+										   PVC_INCLUDE_WINDOWFUNCS);
+
+	Node *expression = NULL;
+	foreach_ptr(expression, expressionList)
+	{
+		/* only consider aggregate expressions */
+		if (!IsA(expression, Aggref))
+		{
+			continue;
+		}
+
+		AggregateType aggregateType = GetAggregateType((Aggref *) expression);
+		Assert(aggregateType != AGGREGATE_INVALID_FIRST);
+
+		if (aggregateType == AGGREGATE_CUSTOM_ROW_GATHER)
+		{
+			return true;
+		}
+	}
+
+	return false;
+}
+
+
+/*
+ * DeferErrorIfContainsNonPushdownableAggregate extracts aggregate expressions from
+ * the logical plan, walks over them and uses helper functions to check if we
+ * can transform these aggregate expressions and push them down to worker nodes.
+ */
+static DeferredErrorMessage *
+DeferErrorIfContainsNonPushdownableAggregate(MultiNode *logicalPlanNode)
+{
+	DeferredErrorMessage *error = NULL;
 	List *opNodeList = FindNodesOfType(logicalPlanNode, T_MultiExtendedOp);
 	MultiExtendedOp *extendedOpNode = (MultiExtendedOp *) linitial(opNodeList);
 
@@ -3380,92 +3559,119 @@ ErrorIfContainsUnsupportedAggregate(MultiNode *logicalPlanNode)
 		 */
 		if (aggregateType == AGGREGATE_ARRAY_AGG)
 		{
-			ErrorIfUnsupportedArrayAggregate(aggregateExpression);
+			error = DeferErrorIfUnsupportedArrayAggregate(aggregateExpression);
 		}
 		else if (aggregateType == AGGREGATE_JSONB_AGG ||
 				 aggregateType == AGGREGATE_JSON_AGG)
 		{
-			ErrorIfUnsupportedJsonAggregate(aggregateType, aggregateExpression);
+			error = DeferErrorIfUnsupportedJsonAggregate(aggregateType,
+														 aggregateExpression);
 		}
 		else if (aggregateType == AGGREGATE_JSONB_OBJECT_AGG ||
 				 aggregateType == AGGREGATE_JSON_OBJECT_AGG)
 		{
-			ErrorIfUnsupportedJsonAggregate(aggregateType, aggregateExpression);
+			error = DeferErrorIfUnsupportedJsonAggregate(aggregateType,
+														 aggregateExpression);
 		}
 		else if (aggregateExpression->aggdistinct)
 		{
-			ErrorIfUnsupportedAggregateDistinct(aggregateExpression, logicalPlanNode);
+			error = DeferErrorIfUnsupportedAggregateDistinct(aggregateExpression,
+															 logicalPlanNode);
+		}
+
+		if (error != NULL)
+		{
+			return error;
 		}
 	}
+
+	return NULL;
 }
 
 
 /*
- * ErrorIfUnsupportedArrayAggregate checks if we can transform the array aggregate
+ * DeferErrorIfUnsupportedArrayAggregate checks if we can transform the array aggregate
  * expression and push it down to the worker node. If we cannot transform the
  * aggregate, this function errors.
  */
-static void
-ErrorIfUnsupportedArrayAggregate(Aggref *arrayAggregateExpression)
+static DeferredErrorMessage *
+DeferErrorIfUnsupportedArrayAggregate(Aggref *arrayAggregateExpression)
 {
 	/* if array_agg has order by, we error out */
 	if (arrayAggregateExpression->aggorder)
 	{
-		ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-						errmsg("array_agg with order by is unsupported")));
+		return DeferredError(ERRCODE_FEATURE_NOT_SUPPORTED,
+							 "array_agg with order by is unsupported",
+							 NULL, NULL);
 	}
 
 	/* if array_agg has distinct, we error out */
 	if (arrayAggregateExpression->aggdistinct)
 	{
-		ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-						errmsg("array_agg (distinct) is unsupported")));
+		return DeferredError(ERRCODE_FEATURE_NOT_SUPPORTED,
+							 "array_agg (distinct) is unsupported",
+							 NULL, NULL);
 	}
+
+	return NULL;
 }
 
 
 /*
- * ErrorIfUnsupportedJsonAggregate checks if we can transform the json
+ * DeferErrorIfUnsupportedJsonAggregate checks if we can transform the json
  * aggregate expression and push it down to the worker node. If we cannot
  * transform the aggregate, this function errors.
  */
-static void
-ErrorIfUnsupportedJsonAggregate(AggregateType type,
+static DeferredErrorMessage *
+DeferErrorIfUnsupportedJsonAggregate(AggregateType type,
 									 Aggref *aggregateExpression)
 {
 	/* if json aggregate has order by, we error out */
+	if (aggregateExpression->aggdistinct || aggregateExpression->aggorder)
+	{
+		StringInfoData errorDetail;
+		initStringInfo(&errorDetail);
+		const char *name = AggregateNames[type];
+
+		appendStringInfoString(&errorDetail, name);
 		if (aggregateExpression->aggorder)
 		{
-		const char *name = AggregateNames[type];
-		ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-						errmsg("%s with order by is unsupported", name)));
+			appendStringInfoString(&errorDetail, " with order by is unsupported");
+		}
+		else
+		{
+			appendStringInfoString(&errorDetail, " (distinct) is unsupported");
 		}
 
-	/* if json aggregate has distinct, we error out */
-	if (aggregateExpression->aggdistinct)
-	{
-		const char *name = AggregateNames[type];
-		ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-						errmsg("%s (distinct) is unsupported", name)));
+		return DeferredError(ERRCODE_FEATURE_NOT_SUPPORTED, errorDetail.data,
+							 NULL, NULL);
 	}
+
+	return NULL;
 }
 
 
 /*
- * ErrorIfUnsupportedAggregateDistinct checks if we can transform the aggregate
+ * DeferErrorIfUnsupportedAggregateDistinct checks if we can transform the aggregate
  * (distinct expression) and push it down to the worker node. It handles count
  * (distinct) separately to check if we can use distinct approximations. If we
  * cannot transform the aggregate, this function errors.
  */
-static void
-ErrorIfUnsupportedAggregateDistinct(Aggref *aggregateExpression,
+static DeferredErrorMessage *
+DeferErrorIfUnsupportedAggregateDistinct(Aggref *aggregateExpression,
 										 MultiNode *logicalPlanNode)
 {
-	char *errorDetail = NULL;
+	const char *errorDetail = NULL;
 	bool distinctSupported = true;
 
 	AggregateType aggregateType = GetAggregateType(aggregateExpression);
 
+	/* If we're aggregating on coordinator, this becomes simple. */
+	if (aggregateType == AGGREGATE_CUSTOM_ROW_GATHER)
+	{
+		return NULL;
+	}
+
 	/*
 	 * We partially support count(distinct) in subqueries, other distinct aggregates in
 	 * subqueries are not supported yet.
@@ -3480,9 +3686,10 @@ ErrorIfUnsupportedAggregateDistinct(Aggref *aggregateExpression,
 			Var *column = (Var *) lfirst(columnCell);
 			if (column->varattno <= 0)
 			{
-				ereport(ERROR, (errmsg("cannot compute count (distinct)"),
-								errdetail("Non-column references are not supported "
-										  "yet")));
+				return DeferredError(ERRCODE_FEATURE_NOT_SUPPORTED,
+									 "cannot compute count (distinct)",
+									 "Non-column references are not supported yet",
+									 NULL);
 			}
 		}
 	}
@@ -3496,9 +3703,10 @@ ErrorIfUnsupportedAggregateDistinct(Aggref *aggregateExpression,
 			if (multiTable->relationId == SUBQUERY_RELATION_ID ||
 				multiTable->relationId == SUBQUERY_PUSHDOWN_RELATION_ID)
 			{
-				ereport(ERROR, (errmsg("cannot compute aggregate (distinct)"),
-								errdetail("Only count(distinct) aggregate is "
-										  "supported in subqueries")));
+				return DeferredError(ERRCODE_FEATURE_NOT_SUPPORTED,
+									 "cannot compute aggregate (distinct)",
+									 "Only count(distinct) aggregate is "
+									 "supported in subqueries", NULL);
 			}
 		}
 	}
@@ -3513,12 +3721,14 @@ ErrorIfUnsupportedAggregateDistinct(Aggref *aggregateExpression,
 		/* if extension for distinct approximation is loaded, we are good */
 		if (distinctExtensionId != InvalidOid)
 		{
-			return;
+			return NULL;
 		}
 		else
 		{
-			ereport(ERROR, (errmsg("cannot compute count (distinct) approximation"),
-							errhint("You need to have the hll extension loaded.")));
+			return DeferredError(ERRCODE_FEATURE_NOT_SUPPORTED,
+								 "cannot compute count (distinct) approximation",
+								 NULL,
+								 "You need to have the hll extension loaded.");
 		}
 	}
 
@@ -3580,21 +3790,19 @@ ErrorIfUnsupportedAggregateDistinct(Aggref *aggregateExpression,
 	/* if current aggregate expression isn't supported, error out */
 	if (!distinctSupported)
 	{
+		const char *errorHint = NULL;
 		if (aggregateType == AGGREGATE_COUNT)
 		{
-			ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-							errmsg("cannot compute aggregate (distinct)"),
-							errdetail("%s", errorDetail),
-							errhint("You can load the hll extension from contrib "
-									"packages and enable distinct approximations.")));
-		}
-		else
-		{
-			ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-							errmsg("cannot compute aggregate (distinct)"),
-							errdetail("%s", errorDetail)));
+			errorHint = "You can load the hll extension from contrib "
+						"packages and enable distinct approximations.";
 		}
+
+		return DeferredError(ERRCODE_FEATURE_NOT_SUPPORTED,
+							 "cannot compute aggregate (distinct)",
+							 errorDetail, errorHint);
 	}
+
+	return NULL;
 }
 
 

src/backend/distributed/planner/multi_master_planner.c

@@ -50,7 +50,7 @@ static List * MasterTargetList(List *workerTargetList);
 static PlannedStmt * BuildSelectStatement(Query *masterQuery, List *masterTargetList,
 										  CustomScan *remoteScan);
 static Agg * BuildAggregatePlan(PlannerInfo *root, Query *masterQuery, Plan *subPlan);
-static bool HasDistinctAggregate(Query *masterQuery);
+static bool HasDistinctOrOrderByAggregate(Query *masterQuery);
 static bool UseGroupAggregateWithHLL(Query *masterQuery);
 static bool QueryContainsAggregateWithHLL(Query *query);
 static Plan * BuildDistinctPlan(Query *masterQuery, Plan *subPlan);
@@ -361,7 +361,7 @@ FinalizeStatement(PlannerInfo *root, PlannedStmt *result, Plan *top_plan)
 
 /*
  * BuildAggregatePlan creates and returns an aggregate plan. This aggregate plan
- * builds aggreation and grouping operators (if any) that are to be executed on
+ * builds aggregation and grouping operators (if any) that are to be executed on
  * the master node.
  */
 static Agg *
@@ -405,7 +405,7 @@ BuildAggregatePlan(PlannerInfo *root, Query *masterQuery, Plan *subPlan)
 	{
 		bool groupingIsHashable = grouping_is_hashable(groupColumnList);
 		bool groupingIsSortable = grouping_is_sortable(groupColumnList);
-		bool hasDistinctAggregate = HasDistinctAggregate(masterQuery);
+		bool hasUnhashableAggregate = HasDistinctOrOrderByAggregate(masterQuery);
 
 		if (!groupingIsHashable && !groupingIsSortable)
 		{
@@ -421,7 +421,7 @@ BuildAggregatePlan(PlannerInfo *root, Query *masterQuery, Plan *subPlan)
 		 * If the master query contains hll aggregate functions and the client set
 		 * hll.force_groupagg to on, then we choose to use group aggregation.
 		 */
-		if (!enable_hashagg || !groupingIsHashable || hasDistinctAggregate ||
+		if (!enable_hashagg || !groupingIsHashable || hasUnhashableAggregate ||
 			UseGroupAggregateWithHLL(masterQuery))
 		{
 			char *messageHint = NULL;
@@ -465,7 +465,7 @@ BuildAggregatePlan(PlannerInfo *root, Query *masterQuery, Plan *subPlan)
  * aggregate in its target list or in having clause.
  */
 static bool
-HasDistinctAggregate(Query *masterQuery)
+HasDistinctOrOrderByAggregate(Query *masterQuery)
 {
 	ListCell *allColumnCell = NULL;
 
@@ -481,7 +481,7 @@ HasDistinctAggregate(Query *masterQuery)
 		if (IsA(columnNode, Aggref))
 		{
 			Aggref *aggref = (Aggref *) columnNode;
-			if (aggref->aggdistinct != NIL)
+			if (aggref->aggdistinct != NIL || aggref->aggorder != NIL)
 			{
 				return true;
 			}
@@ -595,9 +595,9 @@ BuildDistinctPlan(Query *masterQuery, Plan *subPlan)
 	 * Otherwise create sort+unique plan.
 	 */
 	bool distinctClausesHashable = grouping_is_hashable(distinctClauseList);
-	bool hasDistinctAggregate = HasDistinctAggregate(masterQuery);
+	bool hasUnhashableAggregate = HasDistinctOrOrderByAggregate(masterQuery);
 
-	if (enable_hashagg && distinctClausesHashable && !hasDistinctAggregate)
+	if (enable_hashagg && distinctClausesHashable && !hasUnhashableAggregate)
 	{
 		distinctPlan = (Plan *) makeAggNode(distinctClauseList, NIL, AGG_HASHED,
 											targetList, subPlan);

src/backend/distributed/shared_library_init.c

@@ -140,6 +140,12 @@ static const struct config_enum_entry use_secondary_nodes_options[] = {
 	{ NULL, 0, false }
 };
 
+static const struct config_enum_entry coordinator_aggregation_options[] = {
+	{ "disabled", COORDINATOR_AGGREGATION_DISABLED, false },
+	{ "row-gather", COORDINATOR_AGGREGATION_ROW_GATHER, false },
+	{ NULL, 0, false }
+};
+
 static const struct config_enum_entry shard_commit_protocol_options[] = {
 	{ "1pc", COMMIT_PROTOCOL_1PC, false },
 	{ "2pc", COMMIT_PROTOCOL_2PC, false },
@@ -1006,6 +1012,19 @@ RegisterCitusConfigVariables(void)
 		GUC_STANDARD,
 		NULL, NULL, NULL);
 
+	DefineCustomEnumVariable(
+		"citus.coordinator_aggregation_strategy",
+		gettext_noop("Sets the strategy for when an aggregate cannot be pushed down. "
+					 "'row-gather' will pull up intermediate rows to the coordinator, "
+					 "while 'disabled' will error if coordinator aggregation is necessary"),
+		NULL,
+		&CoordinatorAggregationStrategy,
+		COORDINATOR_AGGREGATION_ROW_GATHER,
+		coordinator_aggregation_options,
+		PGC_USERSET,
+		GUC_STANDARD,
+		NULL, NULL, NULL);
+
 	DefineCustomEnumVariable(
 		"citus.multi_shard_commit_protocol",
 		gettext_noop("Sets the commit protocol for commands modifying multiple shards."),

src/include/distributed/extended_op_node_utils.h

@@ -28,11 +28,12 @@ typedef struct ExtendedOpNodeProperties
 	bool hasNonPartitionColumnDistinctAgg;
 	bool pullDistinctColumns;
 	bool pushDownWindowFunctions;
+	bool pullUpIntermediateRows;
 } ExtendedOpNodeProperties;
 
 
-extern ExtendedOpNodeProperties BuildExtendedOpNodeProperties(MultiExtendedOp *
-															  extendedOpNode);
+extern ExtendedOpNodeProperties BuildExtendedOpNodeProperties(
+	MultiExtendedOp *extendedOpNode, bool pullUpIntermediateRows);
 
 
 #endif /* EXTENDED_OP_NODE_UTILS_H_ */

src/include/distributed/multi_logical_optimizer.h

@@ -81,9 +81,19 @@ typedef enum
 	AGGREGATE_ANY_VALUE = 20,
 
 	/* AGGREGATE_CUSTOM must come last */
-	AGGREGATE_CUSTOM = 21
+	AGGREGATE_CUSTOM_COMBINE = 21,
+	AGGREGATE_CUSTOM_ROW_GATHER = 22,
 } AggregateType;
 
+
+/* Enumeration for citus.coordinator_aggregation GUC */
+typedef enum
+{
+	COORDINATOR_AGGREGATION_DISABLED,
+	COORDINATOR_AGGREGATION_ROW_GATHER,
+} CoordinatorAggregationStrategyType;
+
+
 /*
  * PushDownStatus indicates whether a node can be pushed down below its child
  * using the commutative and distributive relational algebraic properties.
@@ -135,6 +145,7 @@ static const char *const AggregateNames[] = {
 /* Config variable managed via guc.c */
 extern int LimitClauseRowFetchCount;
 extern double CountDistinctErrorRate;
+extern int CoordinatorAggregationStrategy;
 
 
 /* Function declaration for optimizing logical plans */

src/test/regress/expected/aggregate_support.out

@@ -4,6 +4,7 @@
 -- Tests support for user defined aggregates
 create schema aggregate_support;
 set search_path to aggregate_support;
+set citus.coordinator_aggregation_strategy to 'disabled';
 -- We test with & without STRICT as our code is responsible for managing these NULL checks
 create function sum2_sfunc_strict(state int, x int)
 returns int immutable strict language plpgsql as $$
@@ -113,6 +114,19 @@ select sum2(val), sum2_strict(val) from aggdata where valf = 0;
     0 |
 (1 row)
 
+-- Test HAVING
+select key, stddev(valf) from aggdata group by key having stddev(valf) > 2 order by key;
+ key |      stddev
+---------------------------------------------------------------------
+   1 | 6.43467170879758
+(1 row)
+
+select key, stddev(valf) from aggdata group by key having stddev(val::float8) > 1 order by key;
+ key |      stddev
+---------------------------------------------------------------------
+   2 | 1.01500410508201
+(1 row)
+
 -- test polymorphic aggregates from https://github.com/citusdata/citus/issues/2397
 -- we do not currently support pseudotypes for transition types, so this errors for now
 CREATE OR REPLACE FUNCTION first_agg(anyelement, anyelement)
@@ -255,5 +269,139 @@ select array_collect_sort(val) from aggdata;
 (1 row)
 
 reset role;
+-- Test aggregation on coordinator
+set citus.coordinator_aggregation_strategy to 'row-gather';
+select key, first(val order by id), last(val order by id)
+from aggdata group by key order by key;
+ key | first | last
+---------------------------------------------------------------------
+   1 |     2 |
+   2 |     2 |    5
+   3 |     4 |    4
+   5 |       |
+   6 |       |
+   7 |     8 |    8
+   9 |     0 |    0
+(7 rows)
+
+select key, sum2(distinct val), sum2_strict(distinct val) from aggdata group by key order by key;
+ key | sum2 | sum2_strict
+---------------------------------------------------------------------
+   1 |      |           4
+   2 |   20 |          20
+   3 |    8 |           8
+   5 |      |
+   6 |      |
+   7 |   16 |          16
+   9 |    0 |           0
+(7 rows)
+
+select key, sum2(val order by valf), sum2_strict(val order by valf) from aggdata group by key order by key;
+ key | sum2 | sum2_strict
+---------------------------------------------------------------------
+   1 |      |           4
+   2 |   20 |          20
+   3 |    8 |           8
+   5 |      |
+   6 |      |
+   7 |   16 |          16
+   9 |    0 |           0
+(7 rows)
+
+select string_agg(distinct floor(val/2)::text, '|' order by floor(val/2)::text) from aggdata;
+ string_agg
+---------------------------------------------------------------------
+ 0|1|2|4
+(1 row)
+
+select string_agg(distinct floor(val/2)::text, '|' order by floor(val/2)::text) filter (where val < 5) from aggdata;
+ string_agg
+---------------------------------------------------------------------
+ 0|1|2
+(1 row)
+
+select mode() within group (order by floor(val/2)) from aggdata;
+ mode
+---------------------------------------------------------------------
+    1
+(1 row)
+
+select percentile_cont(0.5) within group(order by valf) from aggdata;
+ percentile_cont
+---------------------------------------------------------------------
+           8.225
+(1 row)
+
+select key, percentile_cont(key/10.0) within group(order by val) from aggdata group by key;
+ key | percentile_cont
+---------------------------------------------------------------------
+   1 |               2
+   2 |             2.4
+   3 |               4
+   5 |
+   6 |
+   7 |               8
+   9 |               0
+(7 rows)
+
+select floor(val/2), corr(valf, valf + val) from aggdata group by floor(val/2) order by 1;
+ floor |       corr
+---------------------------------------------------------------------
+     0 |
+     1 | 0.991808518376741
+     2 |                 1
+     4 |
+       |
+(5 rows)
+
+select floor(val/2), corr(valf, valf + val) from aggdata group by floor(val/2) having corr(valf + val, val) < 1 order by 1;
+ floor |       corr
+---------------------------------------------------------------------
+     1 | 0.991808518376741
+     2 |                 1
+(2 rows)
+
+select array_agg(val order by valf) from aggdata;
+              array_agg
+---------------------------------------------------------------------
+ {0,NULL,2,3,5,2,4,NULL,NULL,8,NULL}
+(1 row)
+
+-- Test TransformSubqueryNode
+SET citus.task_executor_type to "task-tracker";
+select * FROM (
+    SELECT key, mode() within group (order by floor(agg1.val/2)) m from aggdata agg1
+    group by key
+) subq ORDER BY 2, 1 LIMIT 5;
+ key | m
+---------------------------------------------------------------------
+   9 | 0
+   1 | 1
+   2 | 1
+   3 | 2
+   7 | 4
+(5 rows)
+
+select * FROM (
+    SELECT key, avg(distinct floor(agg1.val/2)) m from aggdata agg1
+    group by key
+) subq;
+ key |  m
+---------------------------------------------------------------------
+   1 |   1
+   5 |
+   3 |   2
+   7 |   4
+   6 |
+   2 | 1.5
+   9 |   0
+(7 rows)
+
+RESET citus.task_executor_type;
+-- This fails due to table types not being managed properly
+select key, count(distinct aggdata)
+from aggdata group by key order by 1, 2;
+ERROR:  type "aggregate_support.aggdata" does not exist
+CONTEXT:  while executing command on localhost:xxxxx
 set client_min_messages to error;
 drop schema aggregate_support cascade;

src/test/regress/expected/custom_aggregate_support.out

@@ -11,6 +11,7 @@ WHERE name = 'hll'
 :create_cmd;
 ERROR:  extension "hll" already exists
 SET citus.shard_count TO 4;
+set citus.coordinator_aggregation_strategy to 'disabled';
 CREATE TABLE raw_table (day date, user_id int);
 CREATE TABLE daily_uniques(day date, unique_users hll);
 SELECT create_distributed_table('raw_table', 'user_id');

src/test/regress/expected/custom_aggregate_support_0.out

@@ -15,6 +15,7 @@ WHERE name = 'hll'
 (1 row)
 
 SET citus.shard_count TO 4;
+set citus.coordinator_aggregation_strategy to 'disabled';
 CREATE TABLE raw_table (day date, user_id int);
 CREATE TABLE daily_uniques(day date, unique_users hll);
 ERROR:  type "hll" does not exist

src/test/regress/expected/custom_aggregate_support_1.out

@@ -11,6 +11,7 @@ WHERE name = 'hll'
 :create_cmd;
 ERROR:  extension "hll" already exists
 SET citus.shard_count TO 4;
+set citus.coordinator_aggregation_strategy to 'disabled';
 CREATE TABLE raw_table (day date, user_id int);
 CREATE TABLE daily_uniques(day date, unique_users hll);
 SELECT create_distributed_table('raw_table', 'user_id');

src/test/regress/expected/multi_agg_approximate_distinct.out

@@ -9,6 +9,7 @@ AS create_cmd FROM pg_available_extensions()
 WHERE name = 'hll'
 \gset
 :create_cmd;
+SET citus.coordinator_aggregation_strategy TO 'disabled';
 -- Try to execute count(distinct) when approximate distincts aren't enabled
 SELECT count(distinct l_orderkey) FROM lineitem;
  count

src/test/regress/expected/multi_agg_approximate_distinct_0.out

@@ -14,6 +14,7 @@ WHERE name = 'hll'
  f
 (1 row)
 
+SET citus.coordinator_aggregation_strategy TO 'disabled';
 -- Try to execute count(distinct) when approximate distincts aren't enabled
 SELECT count(distinct l_orderkey) FROM lineitem;
  count

src/test/regress/expected/multi_array_agg.out

@@ -2,6 +2,7 @@
 -- MULTI_ARRAY_AGG
 --
 SET citus.next_shard_id TO 520000;
+SET citus.coordinator_aggregation_strategy TO 'disabled';
 CREATE OR REPLACE FUNCTION array_sort (ANYARRAY)
 RETURNS ANYARRAY LANGUAGE SQL
 AS $$

src/test/regress/expected/multi_json_agg.out

@@ -2,6 +2,7 @@
 -- MULTI_JSON_AGG
 --
 SET citus.next_shard_id TO 520000;
+SET citus.coordinator_aggregation_strategy TO 'disabled';
 CREATE OR REPLACE FUNCTION array_sort (json)
 RETURNS json LANGUAGE SQL
 AS $$

src/test/regress/expected/multi_json_object_agg.out

@@ -2,6 +2,7 @@
 -- MULTI_JSON_OBJECT_AGG
 --
 SET citus.next_shard_id TO 520000;
+SET citus.coordinator_aggregation_strategy TO 'disabled';
 CREATE OR REPLACE FUNCTION count_keys (json)
 RETURNS bigint LANGUAGE SQL
 AS $$

src/test/regress/expected/multi_jsonb_agg.out

@@ -2,6 +2,7 @@
 -- MULTI_JSONB_AGG
 --
 SET citus.next_shard_id TO 520000;
+SET citus.coordinator_aggregation_strategy TO 'disabled';
 CREATE OR REPLACE FUNCTION array_sort (jsonb)
 RETURNS jsonb LANGUAGE SQL
 AS $$

src/test/regress/expected/multi_jsonb_object_agg.out

@@ -2,6 +2,7 @@
 -- MULTI_JSONB_OBJECT_AGG
 --
 SET citus.next_shard_id TO 520000;
+SET citus.coordinator_aggregation_strategy TO 'disabled';
 CREATE OR REPLACE FUNCTION count_keys (jsonb)
 RETURNS bigint LANGUAGE SQL
 AS $$

src/test/regress/expected/multi_simple_queries.out

@@ -3,6 +3,7 @@ SET citus.next_shard_id TO 850000;
 -- router planner, so we're explicitly disabling it in this file.
 -- We've bunch of other tests that triggers fast-path-router
 SET citus.enable_fast_path_router_planner TO false;
+SET citus.coordinator_aggregation_strategy TO 'disabled';
 -- ===================================================================
 -- test end-to-end query functionality
 -- ===================================================================

src/test/regress/expected/multi_simple_queries_0.out

@@ -3,6 +3,7 @@ SET citus.next_shard_id TO 850000;
 -- router planner, so we're explicitly disabling it in this file.
 -- We've bunch of other tests that triggers fast-path-router
 SET citus.enable_fast_path_router_planner TO false;
+SET citus.coordinator_aggregation_strategy TO 'disabled';
 -- ===================================================================
 -- test end-to-end query functionality
 -- ===================================================================

src/test/regress/expected/multi_subquery.out

@@ -3,6 +3,7 @@
 --
 -- no need to set shardid sequence given that we're not creating any shards
 SET citus.next_shard_id TO 570032;
+SET citus.coordinator_aggregation_strategy TO 'disabled';
 -- Check that we error out if shard min/max values are not exactly same.
 SELECT
 	avg(unit_price)

src/test/regress/expected/set_operations.out

@@ -1,5 +1,6 @@
 CREATE SCHEMA recursive_union;
 SET search_path TO recursive_union, public;
+SET citus.coordinator_aggregation_strategy TO 'disabled';
 CREATE TABLE recursive_union.test (x int, y int);
 SELECT create_distributed_table('test', 'x');
  create_distributed_table

src/test/regress/expected/subqueries_not_supported.out

@@ -3,6 +3,7 @@
 -- ===================================================================
 CREATE SCHEMA not_supported;
 SET search_path TO not_supported, public;
+SET citus.coordinator_aggregation_strategy TO 'disabled';
 SET client_min_messages TO DEBUG1;
 CREATE TABLE users_table_local AS SELECT * FROM users_table;
 -- we don't support subqueries with local tables when they are not leaf queries

src/test/regress/expected/with_basics.out

@@ -1,5 +1,6 @@
 -- Test the basic CTE functionality and expected error messages
 SET search_path TO 'with_basics';
+SET citus.coordinator_aggregation_strategy TO 'disabled';
 CREATE TYPE with_basics.xy AS (x int, y int);
 -- CTEs in FROM should work
 WITH cte AS (

src/test/regress/input/multi_agg_distinct.source

@@ -2,6 +2,7 @@
 -- MULTI_AGG_DISTINCT
 --
 
+SET citus.coordinator_aggregation_strategy TO 'disabled';
 
 -- Create a new range partitioned lineitem table and load data into it
 CREATE TABLE lineitem_range (

src/test/regress/input/multi_complex_count_distinct.source

@@ -6,6 +6,7 @@
 SET citus.next_shard_id TO 240000;
 SET citus.shard_count TO 8;
 SET citus.shard_replication_factor TO 1;
+SET citus.coordinator_aggregation_strategy TO 'disabled';
 
 CREATE TABLE lineitem_hash (
 	l_orderkey bigint not null,

src/test/regress/output/multi_agg_distinct.source

@@ -1,6 +1,7 @@
 --
 -- MULTI_AGG_DISTINCT
 --
+SET citus.coordinator_aggregation_strategy TO 'disabled';
 -- Create a new range partitioned lineitem table and load data into it
 CREATE TABLE lineitem_range (
 	l_orderkey bigint not null,

src/test/regress/output/multi_complex_count_distinct.source

@@ -4,6 +4,7 @@
 SET citus.next_shard_id TO 240000;
 SET citus.shard_count TO 8;
 SET citus.shard_replication_factor TO 1;
+SET citus.coordinator_aggregation_strategy TO 'disabled';
 CREATE TABLE lineitem_hash (
 	l_orderkey bigint not null,
 	l_partkey integer not null,

src/test/regress/sql/aggregate_support.sql

@@ -5,6 +5,7 @@
 
 create schema aggregate_support;
 set search_path to aggregate_support;
+set citus.coordinator_aggregation_strategy to 'disabled';
 
 -- We test with & without STRICT as our code is responsible for managing these NULL checks
 create function sum2_sfunc_strict(state int, x int)
@@ -63,6 +64,9 @@ select id, sum2(distinct val), sum2_strict(distinct val) from aggdata group by i
 select key, sum2(val order by valf), sum2_strict(val order by valf) from aggdata group by key order by key;
 -- Test handling a lack of intermediate results
 select sum2(val), sum2_strict(val) from aggdata where valf = 0;
+-- Test HAVING
+select key, stddev(valf) from aggdata group by key having stddev(valf) > 2 order by key;
+select key, stddev(valf) from aggdata group by key having stddev(val::float8) > 1 order by key;
 
 
 -- test polymorphic aggregates from https://github.com/citusdata/citus/issues/2397
@@ -154,5 +158,41 @@ set role notsuper;
 select array_collect_sort(val) from aggdata;
 reset role;
 
+-- Test aggregation on coordinator
+set citus.coordinator_aggregation_strategy to 'row-gather';
+
+select key, first(val order by id), last(val order by id)
+from aggdata group by key order by key;
+
+select key, sum2(distinct val), sum2_strict(distinct val) from aggdata group by key order by key;
+select key, sum2(val order by valf), sum2_strict(val order by valf) from aggdata group by key order by key;
+select string_agg(distinct floor(val/2)::text, '|' order by floor(val/2)::text) from aggdata;
+select string_agg(distinct floor(val/2)::text, '|' order by floor(val/2)::text) filter (where val < 5) from aggdata;
+select mode() within group (order by floor(val/2)) from aggdata;
+select percentile_cont(0.5) within group(order by valf) from aggdata;
+select key, percentile_cont(key/10.0) within group(order by val) from aggdata group by key;
+select floor(val/2), corr(valf, valf + val) from aggdata group by floor(val/2) order by 1;
+select floor(val/2), corr(valf, valf + val) from aggdata group by floor(val/2) having corr(valf + val, val) < 1 order by 1;
+select array_agg(val order by valf) from aggdata;
+
+-- Test TransformSubqueryNode
+SET citus.task_executor_type to "task-tracker";
+
+select * FROM (
+    SELECT key, mode() within group (order by floor(agg1.val/2)) m from aggdata agg1
+    group by key
+) subq ORDER BY 2, 1 LIMIT 5;
+
+select * FROM (
+    SELECT key, avg(distinct floor(agg1.val/2)) m from aggdata agg1
+    group by key
+) subq;
+
+RESET citus.task_executor_type;
+
+-- This fails due to table types not being managed properly
+select key, count(distinct aggdata)
+from aggdata group by key order by 1, 2;
+
 set client_min_messages to error;
 drop schema aggregate_support cascade;

src/test/regress/sql/custom_aggregate_support.sql

@@ -12,6 +12,7 @@ WHERE name = 'hll'
 :create_cmd;
 
 SET citus.shard_count TO 4;
+set citus.coordinator_aggregation_strategy to 'disabled';
 
 CREATE TABLE raw_table (day date, user_id int);
 CREATE TABLE daily_uniques(day date, unique_users hll);

src/test/regress/sql/multi_agg_approximate_distinct.sql

@@ -13,6 +13,8 @@ WHERE name = 'hll'
 
 :create_cmd;
 
+SET citus.coordinator_aggregation_strategy TO 'disabled';
+
 -- Try to execute count(distinct) when approximate distincts aren't enabled
 
 SELECT count(distinct l_orderkey) FROM lineitem;

src/test/regress/sql/multi_array_agg.sql

@@ -4,6 +4,7 @@
 
 
 SET citus.next_shard_id TO 520000;
+SET citus.coordinator_aggregation_strategy TO 'disabled';
 
 CREATE OR REPLACE FUNCTION array_sort (ANYARRAY)
 RETURNS ANYARRAY LANGUAGE SQL

src/test/regress/sql/multi_json_agg.sql

@@ -4,6 +4,7 @@
 
 
 SET citus.next_shard_id TO 520000;
+SET citus.coordinator_aggregation_strategy TO 'disabled';
 
 CREATE OR REPLACE FUNCTION array_sort (json)
 RETURNS json LANGUAGE SQL

src/test/regress/sql/multi_json_object_agg.sql

@@ -4,6 +4,7 @@
 
 
 SET citus.next_shard_id TO 520000;
+SET citus.coordinator_aggregation_strategy TO 'disabled';
 
 CREATE OR REPLACE FUNCTION count_keys (json)
 RETURNS bigint LANGUAGE SQL

src/test/regress/sql/multi_jsonb_agg.sql

@@ -4,6 +4,7 @@
 
 
 SET citus.next_shard_id TO 520000;
+SET citus.coordinator_aggregation_strategy TO 'disabled';
 
 CREATE OR REPLACE FUNCTION array_sort (jsonb)
 RETURNS jsonb LANGUAGE SQL

src/test/regress/sql/multi_jsonb_object_agg.sql

@@ -4,6 +4,7 @@
 
 
 SET citus.next_shard_id TO 520000;
+SET citus.coordinator_aggregation_strategy TO 'disabled';
 
 CREATE OR REPLACE FUNCTION count_keys (jsonb)
 RETURNS bigint LANGUAGE SQL

src/test/regress/sql/multi_simple_queries.sql

@@ -5,6 +5,7 @@ SET citus.next_shard_id TO 850000;
 -- router planner, so we're explicitly disabling it in this file.
 -- We've bunch of other tests that triggers fast-path-router
 SET citus.enable_fast_path_router_planner TO false;
+SET citus.coordinator_aggregation_strategy TO 'disabled';
 
 -- ===================================================================
 -- test end-to-end query functionality

src/test/regress/sql/multi_subquery.sql

@@ -4,6 +4,7 @@
 -- no need to set shardid sequence given that we're not creating any shards
 
 SET citus.next_shard_id TO 570032;
+SET citus.coordinator_aggregation_strategy TO 'disabled';
 
 -- Check that we error out if shard min/max values are not exactly same.
 SELECT

src/test/regress/sql/set_operations.sql

@@ -1,5 +1,6 @@
 CREATE SCHEMA recursive_union;
 SET search_path TO recursive_union, public;
+SET citus.coordinator_aggregation_strategy TO 'disabled';
 
 CREATE TABLE recursive_union.test (x int, y int);
 SELECT create_distributed_table('test', 'x');

src/test/regress/sql/subqueries_not_supported.sql

@@ -3,6 +3,7 @@
 -- ===================================================================
 CREATE SCHEMA not_supported;
 SET search_path TO not_supported, public;
+SET citus.coordinator_aggregation_strategy TO 'disabled';
 
 SET client_min_messages TO DEBUG1;
 

src/test/regress/sql/with_basics.sql

@@ -1,5 +1,6 @@
 -- Test the basic CTE functionality and expected error messages
 SET search_path TO 'with_basics';
+SET citus.coordinator_aggregation_strategy TO 'disabled';
 CREATE TYPE with_basics.xy AS (x int, y int);
 
 -- CTEs in FROM should work