diff --git a/src/backend/commands/trigger.c b/src/backend/commands/trigger.c
index ebccfea..ea26615 100644
--- a/src/backend/commands/trigger.c
+++ b/src/backend/commands/trigger.c
@@ -3889,6 +3889,17 @@ afterTriggerInvokeEvents(AfterTriggerEventList *events,
 	return all_fired;
 }
 
+/* ----------
+ * AfterTriggerQueueIsEmpty()
+ *
+ *	True if there are no pending triggers in the queue.
+ * ----------
+ */
+bool
+AfterTriggerQueueIsEmpty(void)
+{
+	return (afterTriggers.query_depth == -1 && afterTriggers.events.head == NULL);
+}
 
 /* ----------
  * AfterTriggerBeginXact()
diff --git a/src/backend/executor/execUtils.c b/src/backend/executor/execUtils.c
index d5e1273..96452dc 100644
--- a/src/backend/executor/execUtils.c
+++ b/src/backend/executor/execUtils.c
@@ -45,6 +45,7 @@
 #include "access/relscan.h"
 #include "access/transam.h"
 #include "catalog/index.h"
+#include "commands/trigger.h"
 #include "executor/execdebug.h"
 #include "nodes/nodeFuncs.h"
 #include "parser/parsetree.h"
@@ -661,6 +662,76 @@ get_last_attnums(Node *node, ProjectionInfo *projInfo)
 								  (void *) projInfo);
 }
 
+/*
+ * ExecCanSkipJoin
+ *		Returns True if the join node can be safely skipped without affecting
+ *		query results.
+ */
+bool
+ExecCanSkipJoin(PlanState *planstate)
+{
+	/*
+	 * Currently the only possibility we have of skipping this join node is if
+	 * a foreign key can prove that the join condition will match exactly 1 row
+	 * on the join condition. The checks for this were all done at planning
+	 * time, and any relations that we found foreign keys on that could prove
+	 * this, we marked those relations as skipJoinPossible. Though if this flag
+	 * is true, it still does not mean that we can skip joining to this
+	 * relation. If any changes have been made to records in the referenced
+	 * relation we may not yet have fired the foreign key triggers to cascade
+	 * those changes to the referencing relations, in this case we mustn't skip
+	 * the join as we could produce wrong results by doing so.
+	 *
+	 * Currently this code is quite naive, as we won't allow join skipping if
+	 * there are *any* pending foreign key triggers, on any relation. It may be
+	 * worthwhile to improve this to check if there's any pending triggers for
+	 * the referencing relation in the join.
+	 */
+	if (!AfterTriggerQueueIsEmpty())
+		return false;
+
+	while (planstate != NULL)
+	{
+		switch (nodeTag(planstate))
+		{
+			case T_SeqScanState:
+			case T_IndexOnlyScanState:
+				{
+					Scan *scan = (Scan *) planstate->plan;
+					RangeTblEntry *rte;
+					rte = (RangeTblEntry *) list_nth(planstate->state->es_range_table, scan->scanrelid - 1);
+
+					if (rte->skipJoinPossible)
+						return true;
+					else
+						return false;
+				}
+				break;
+
+			case T_HashState:
+				/* descend to the scan node */
+				planstate = planstate->lefttree;
+				break;
+
+			case T_HashJoinState:
+				{
+					HashJoinState *hjstate = (HashJoinState *)planstate;
+
+					if (HasFlagSkipJoinBoth(hjstate->js.skipflags))
+						return true;
+					else
+						return false;
+				}
+				break;
+
+			default:
+				return false;
+		}
+	}
+	return false;
+}
+
+
 /* ----------------
  *		ExecAssignProjectionInfo
  *
diff --git a/src/backend/executor/nodeHashjoin.c b/src/backend/executor/nodeHashjoin.c
index 7eec3f3..997314e 100644
--- a/src/backend/executor/nodeHashjoin.c
+++ b/src/backend/executor/nodeHashjoin.c
@@ -71,6 +71,7 @@ ExecHashJoin(HashJoinState *node)
 	TupleTableSlot *outerTupleSlot;
 	uint32		hashvalue;
 	int			batchno;
+	int			skipflags;
 
 	/*
 	 * get information from HashJoin node
@@ -113,6 +114,32 @@ ExecHashJoin(HashJoinState *node)
 		switch (node->hj_JoinState)
 		{
 			case HJ_BUILD_HASHTABLE:
+				skipflags = node->js.skipflags;
+
+				/* Can we skip the whole thing? */
+				if (HasFlagSkipJoinBoth(skipflags))
+					return NULL;
+
+				if (HasFlagSkipJoinInner(skipflags))
+				{
+					node->hj_FirstOuterTupleSlot = ExecProcNode(outerNode);
+					if (TupIsNull(node->hj_FirstOuterTupleSlot))
+						return NULL;
+
+					return node->hj_FirstOuterTupleSlot;
+				}
+				else if (HasFlagSkipJoinOuter(skipflags))
+				{
+					TupleTableSlot *result;
+
+					/* bypass the hash node to the node below it */
+					result = ExecProcNode(hashNode->ps.lefttree);
+
+					if (TupIsNull(result))
+						return NULL;
+
+					return result;
+				}
 
 				/*
 				 * First time through: build hash table for inner relation.
@@ -489,6 +516,13 @@ ExecInitHashJoin(HashJoin *node, EState *estate, int eflags)
 	outerPlanState(hjstate) = ExecInitNode(outerNode, estate, eflags);
 	innerPlanState(hjstate) = ExecInitNode((Plan *) hashNode, estate, eflags);
 
+	hjstate->js.skipflags = 0;
+	if (ExecCanSkipJoin(outerPlanState(hjstate)))
+		hjstate->js.skipflags |= EXEC_SKIPJOIN_OUTER;
+
+	if (ExecCanSkipJoin(innerPlanState(hjstate)))
+		hjstate->js.skipflags |= EXEC_SKIPJOIN_INNER;
+
 	/*
 	 * tuple table initialization
 	 */
@@ -578,6 +612,7 @@ ExecInitHashJoin(HashJoin *node, EState *estate, int eflags)
 		Assert(IsA(hclause, OpExpr));
 		lclauses = lappend(lclauses, linitial(fstate->args));
 		rclauses = lappend(rclauses, lsecond(fstate->args));
+
 		hoperators = lappend_oid(hoperators, hclause->opno);
 	}
 	hjstate->hj_OuterHashKeys = lclauses;
diff --git a/src/backend/executor/nodeMergejoin.c b/src/backend/executor/nodeMergejoin.c
index fdf2f4c..49f6125 100644
--- a/src/backend/executor/nodeMergejoin.c
+++ b/src/backend/executor/nodeMergejoin.c
@@ -621,6 +621,7 @@ ExecMergeJoin(MergeJoinState *node)
 	ExprContext *econtext;
 	bool		doFillOuter;
 	bool		doFillInner;
+	int			skipflags;
 
 	/*
 	 * get information from node
@@ -679,6 +680,30 @@ ExecMergeJoin(MergeJoinState *node)
 			case EXEC_MJ_INITIALIZE_OUTER:
 				MJ_printf("ExecMergeJoin: EXEC_MJ_INITIALIZE_OUTER\n");
 
+				skipflags = node->js.skipflags;
+
+				if (HasFlagSkipJoinBoth(skipflags))
+					return NULL;
+
+				if (HasFlagSkipJoinInner(skipflags))
+				{
+					outerTupleSlot = ExecProcNode(outerPlan);
+					if (TupIsNull(outerTupleSlot))
+					{
+						return NULL;
+					}
+					return outerTupleSlot;
+				}
+				else if (HasFlagSkipJoinOuter(skipflags))
+				{
+					innerTupleSlot = ExecProcNode(innerPlan);
+					if (TupIsNull(innerTupleSlot))
+					{
+						return NULL;
+					}
+					return innerTupleSlot;
+				}
+
 				outerTupleSlot = ExecProcNode(outerPlan);
 				node->mj_OuterTupleSlot = outerTupleSlot;
 
@@ -1518,6 +1543,13 @@ ExecInitMergeJoin(MergeJoin *node, EState *estate, int eflags)
 	innerPlanState(mergestate) = ExecInitNode(innerPlan(node), estate,
 											  eflags | EXEC_FLAG_MARK);
 
+	mergestate->js.skipflags = 0;
+	if (ExecCanSkipJoin(outerPlanState(mergestate)))
+		mergestate->js.skipflags |= EXEC_SKIPJOIN_OUTER;
+
+	if (ExecCanSkipJoin(innerPlanState(mergestate)))
+		mergestate->js.skipflags |= EXEC_SKIPJOIN_INNER;
+
 	/*
 	 * For certain types of inner child nodes, it is advantageous to issue
 	 * MARK every time we advance past an inner tuple we will never return to.
diff --git a/src/backend/executor/nodeNestloop.c b/src/backend/executor/nodeNestloop.c
index 6cdd4ff..e0c844f 100644
--- a/src/backend/executor/nodeNestloop.c
+++ b/src/backend/executor/nodeNestloop.c
@@ -68,6 +68,7 @@ ExecNestLoop(NestLoopState *node)
 	List	   *otherqual;
 	ExprContext *econtext;
 	ListCell   *lc;
+	int			skipflags;
 
 	/*
 	 * get information from the node
@@ -105,6 +106,37 @@ ExecNestLoop(NestLoopState *node)
 	 */
 	ResetExprContext(econtext);
 
+	skipflags = node->js.skipflags;
+
+	if (HasFlagSkipJoinAny(skipflags))
+	{
+		if (HasFlagSkipJoinBoth(skipflags))
+			return NULL;
+		else if (HasFlagSkipJoinInner(skipflags))
+		{
+			outerTupleSlot = ExecProcNode(outerPlan);
+
+			if (TupIsNull(outerTupleSlot))
+			{
+				ENL1_printf("no outer tuple, ending join");
+				return NULL;
+			}
+			return outerTupleSlot;
+		}
+		else
+		{
+			innerTupleSlot = ExecProcNode(innerPlan);
+			econtext->ecxt_innertuple = innerTupleSlot;
+
+			if (TupIsNull(innerTupleSlot))
+			{
+				return NULL;
+			}
+
+			return innerTupleSlot;
+		}
+	}
+
 	/*
 	 * Ok, everything is setup for the join so now loop until we return a
 	 * qualifying join tuple.
@@ -347,6 +379,13 @@ ExecInitNestLoop(NestLoop *node, EState *estate, int eflags)
 		eflags &= ~EXEC_FLAG_REWIND;
 	innerPlanState(nlstate) = ExecInitNode(innerPlan(node), estate, eflags);
 
+	nlstate->js.skipflags = 0;
+	if (ExecCanSkipJoin(outerPlanState(nlstate)))
+		nlstate->js.skipflags |= EXEC_SKIPJOIN_OUTER;
+
+	if (ExecCanSkipJoin(innerPlanState(nlstate)))
+		nlstate->js.skipflags |= EXEC_SKIPJOIN_INNER;
+
 	/*
 	 * tuple table initialization
 	 */
diff --git a/src/backend/optimizer/path/equivclass.c b/src/backend/optimizer/path/equivclass.c
index e5dd58e..0a665b2 100644
--- a/src/backend/optimizer/path/equivclass.c
+++ b/src/backend/optimizer/path/equivclass.c
@@ -49,8 +49,6 @@ static List *generate_join_implied_equalities_broken(PlannerInfo *root,
 										Relids outer_relids,
 										Relids nominal_inner_relids,
 										RelOptInfo *inner_rel);
-static Oid select_equality_operator(EquivalenceClass *ec,
-						 Oid lefttype, Oid righttype);
 static RestrictInfo *create_join_clause(PlannerInfo *root,
 				   EquivalenceClass *ec, Oid opno,
 				   EquivalenceMember *leftem,
@@ -1283,7 +1281,7 @@ generate_join_implied_equalities_broken(PlannerInfo *root,
  *
  * Returns InvalidOid if no operator can be found for this datatype combination
  */
-static Oid
+Oid
 select_equality_operator(EquivalenceClass *ec, Oid lefttype, Oid righttype)
 {
 	ListCell   *lc;
diff --git a/src/backend/optimizer/plan/analyzejoins.c b/src/backend/optimizer/plan/analyzejoins.c
index 773f8a4..d5784ea 100644
--- a/src/backend/optimizer/plan/analyzejoins.c
+++ b/src/backend/optimizer/plan/analyzejoins.c
@@ -32,13 +32,21 @@
 #include "utils/lsyscache.h"
 
 /* local functions */
-static bool join_is_removable(PlannerInfo *root, SpecialJoinInfo *sjinfo);
+static bool innerjoin_is_removable(PlannerInfo *root, List *joinlist,
+					  RangeTblRef *removalrtr, Relids ignoredrels);
+static bool leftjoin_is_removable(PlannerInfo *root, SpecialJoinInfo *sjinfo);
+static bool relation_is_needed(PlannerInfo *root, Relids joinrelids,
+					  RelOptInfo *rel, Relids ignoredrels);
+static bool relation_has_foreign_key_for(PlannerInfo *root, RelOptInfo *rel,
+					  RelOptInfo *referencedrel, List *referencing_vars,
+					  List *index_vars, List *operator_list);
+static bool expressions_match_foreign_key(ForeignKeyInfo *fk, List *fkvars,
+					  List *indexvars, List *operators);
 static void remove_rel_from_query(PlannerInfo *root, int relid,
 					  Relids joinrelids);
 static List *remove_rel_from_joinlist(List *joinlist, int relid, int *nremoved);
 static Oid	distinct_col_search(int colno, List *colnos, List *opids);
 
-
 /*
  * remove_useless_joins
  *		Check for relations that don't actually need to be joined at all,
@@ -46,26 +54,91 @@ static Oid	distinct_col_search(int colno, List *colnos, List *opids);
  *
  * We are passed the current joinlist and return the updated list.  Other
  * data structures that have to be updated are accessible via "root".
+ *
+ * There are 2 methods here for removing joins. Joins such as LEFT JOINs
+ * which can be proved to be needless due to lack of use of any of the joining
+ * relation's columns and the existence of a unique index on a subset of the
+ * join clause, can simply be removed from the query plan at plan time. For
+ * certain other join types we make use of foreign keys to attempt to prove the
+ * join is needless, though, for these we're unable to be certain that the join
+ * is not required at plan time, as if the plan is executed when pending
+ * foreign key triggers have not yet been fired, then the foreign key is
+ * effectively violated until these triggers have fired. Removing a join in
+ * such a case could cause a query to produce incorrect results.
+ *
+ * Instead we handle this case by marking the RangeTblEntry for the relation
+ * with a special flag which tells the executor that it's possible that joining
+ * to this relation may not be required. The executor may then check this flag
+ * and choose to skip the join based on if there are foreign key triggers
+ * pending or not.
  */
 List *
 remove_useless_joins(PlannerInfo *root, List *joinlist)
 {
 	ListCell   *lc;
+	Relids		removedrels = NULL;
 
 	/*
-	 * We are only interested in relations that are left-joined to, so we can
-	 * scan the join_info_list to find them easily.
+	 * Start by analyzing INNER JOINed relations in order to determine if any
+	 * of the relations can be ignored.
 	 */
 restart:
+	foreach(lc, joinlist)
+	{
+		RangeTblRef *rtr = (RangeTblRef *) lfirst(lc);
+
+		if (!IsA(rtr, RangeTblRef))
+			continue;
+
+		/* Don't try to remove this one again if we've already removed it */
+		if (root->simple_rte_array[rtr->rtindex]->skipJoinPossible)
+			continue;
+
+		/* skip if the join can't be removed */
+		if (!innerjoin_is_removable(root, joinlist, rtr, removedrels))
+			continue;
+
+		/*
+		 * Since we're not actually removing the join here, we need to maintain
+		 * a list of relations that we've "removed" so when we're checking if
+		 * other relations can be removed we'll know that if the to be removed
+		 * relation is only referenced by a relation that we've already removed
+		 * that it can be safely assumed that the relation is not referenced by
+		 * any useful relation.
+		 */
+		removedrels = bms_add_member(removedrels, rtr->rtindex);
+
+		/*
+		 * Make a mark for the executor to say that it may be able to skip
+		 * joining to this relation.
+		 */
+		root->simple_rte_array[rtr->rtindex]->skipJoinPossible = true;
+
+		/*
+		 * Restart the scan.  This is necessary to ensure we find all removable
+		 * joins independently of their ordering. (note that since we've added
+		 * this relation to the removedrels, we may now realize that other
+		 * relations can also be removed as they're only referenced by the one
+		 * that we've just marked as possibly removable).
+		 */
+		goto restart;
+	}
+
+	/* now process special joins. Currently only left joins are supported */
 	foreach(lc, root->join_info_list)
 	{
 		SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) lfirst(lc);
 		int			innerrelid;
 		int			nremoved;
 
-		/* Skip if not removable */
-		if (!join_is_removable(root, sjinfo))
-			continue;
+		if (sjinfo->jointype == JOIN_LEFT)
+		{
+			/* Skip if not removable */
+			if (!leftjoin_is_removable(root, sjinfo))
+				continue;
+		}
+		else
+			continue; /* we don't support this join type */
 
 		/*
 		 * Currently, join_is_removable can only succeed when the sjinfo's
@@ -91,12 +164,11 @@ restart:
 		root->join_info_list = list_delete_ptr(root->join_info_list, sjinfo);
 
 		/*
-		 * Restart the scan.  This is necessary to ensure we find all
-		 * removable joins independently of ordering of the join_info_list
-		 * (note that removal of attr_needed bits may make a join appear
-		 * removable that did not before).  Also, since we just deleted the
-		 * current list cell, we'd have to have some kluge to continue the
-		 * list scan anyway.
+		 * Restart the scan.  This is necessary to ensure we find all removable
+		 * joins independently of their ordering. (note that removal of
+		 * attr_needed bits may make a join, inner or outer, appear removable
+		 * that did not before).   Also, since we just deleted the current list
+		 * cell, we'd have to have some kluge to continue the list scan anyway.
 		 */
 		goto restart;
 	}
@@ -136,8 +208,213 @@ clause_sides_match_join(RestrictInfo *rinfo, Relids outerrelids,
 }
 
 /*
- * join_is_removable
- *	  Check whether we need not perform this special join at all, because
+ * innerjoin_is_removable
+ *		True if the join to removalrtr can be removed.
+ *
+ * In order to prove a relation which is inner joined is not required we must
+ * be sure that the join would emit exactly 1 row on the join condition. This
+ * differs from the logic which is used for proving LEFT JOINs can be removed,
+ * where it's possible to just check that a unique index exists on the relation
+ * being removed which has a set of columns that is a subset of the columns
+ * seen in the join condition. If no matching row is found then left join would
+ * not remove the non-matched row from the result set. This is not the case
+ * with INNER JOINs, so here we must use foreign keys as proof that the 1 row
+ * exists before we can allow any joins to be removed.
+ */
+static bool
+innerjoin_is_removable(PlannerInfo *root, List *joinlist,
+					   RangeTblRef *removalrtr, Relids ignoredrels)
+{
+	ListCell   *lc;
+	RelOptInfo *removalrel;
+
+	removalrel = find_base_rel(root, removalrtr->rtindex);
+
+	/*
+	 * As foreign keys may only reference base rels which have unique indexes,
+	 * we needn't go any further if we're not dealing with a base rel, or if
+	 * the base rel has no unique indexes. We'd also better abort if the
+	 * rtekind is anything but a relation, as things like sub-queries may have
+	 * grouping or distinct clauses that would cause us not to be able to use
+	 * the foreign key to prove the existence of a row matching the join
+	 * condition. We also abort if the rel has no eclass joins as such a rel
+	 * could well be joined using some operator which is not an equality
+	 * operator, or the rel may not even be inner joined at all.
+	 *
+	 * Here we actually only check if the rel has any indexes, ideally we'd be
+	 * checking for unique indexes, but we could only determine that by looping
+	 * over the indexlist, and this is likely too expensive a check to be worth
+	 * it here.
+	 */
+	if (removalrel->reloptkind != RELOPT_BASEREL ||
+		removalrel->rtekind != RTE_RELATION ||
+		removalrel->has_eclass_joins == false ||
+		removalrel->indexlist == NIL)
+		return false;
+
+	/*
+	 * Currently we disallow the removal if we find any baserestrictinfo items
+	 * on the relation being removed. The reason for this is that these would
+	 * filter out rows and make it so the foreign key cannot prove that we'll
+	 * match exactly 1 row on the join condition. However, this check is
+	 * currently probably a bit overly strict as it should be possible to just
+	 * check and ensure that each Var seen in the baserestrictinfo is also
+	 * present in an eclass and if so, just translate and move the whole
+	 * baserestrictinfo over to the relation which has the foreign key to prove
+	 * that this join is not needed. e.g:
+	 * SELECT a.* FROM a INNER JOIN b ON a.b_id = b.id WHERE b.id = 1;
+	 * could become: SELECT a.* FROM a WHERE a.b_id = 1;
+	 */
+	if (removalrel->baserestrictinfo != NIL)
+		return false;
+
+	/*
+	 * Currently only eclass joins are supported, so if there are any non
+	 * eclass join quals then we'll report the join is non-removable.
+	 */
+	if (removalrel->joininfo != NIL)
+		return false;
+
+	/*
+	 * Now we'll search through each relation in the joinlist to see if we can
+	 * find a relation which has a foreign key which references removalrel on
+	 * the join condition. If we find a rel with a foreign key which matches
+	 * the join condition exactly, then we can be sure that exactly 1 row will
+	 * be matched on the join, if we also see that no Vars from the relation
+	 * are needed, then we can report the join as removable.
+	 */
+	foreach (lc, joinlist)
+	{
+		RangeTblRef	*rtr = (RangeTblRef *) lfirst(lc);
+		RelOptInfo	*rel;
+		ListCell	*lc2;
+		List		*referencing_vars;
+		List		*index_vars;
+		List		*operator_list;
+		Relids		 joinrelids;
+
+		/* we can't remove ourself, or anything other than RangeTblRefs */
+		if (rtr == removalrtr || !IsA(rtr, RangeTblRef))
+			continue;
+
+		rel = find_base_rel(root, rtr->rtindex);
+
+		/*
+		 * The only relation type that can help us is a base rel with at least
+		 * one foreign key defined, if there's no eclass joins then this rel
+		 * is not going to help us prove the removalrel is not needed.
+		 */
+		if (rel->reloptkind != RELOPT_BASEREL ||
+			rel->rtekind != RTE_RELATION ||
+			rel->has_eclass_joins == false ||
+			rel->fklist == NIL)
+			continue;
+
+		/*
+		 * Both rels have eclass joins, but do they have eclass joins to each
+		 * other? Skip this rel if it does not.
+		 */
+		if (!have_relevant_eclass_joinclause(root, rel, removalrel))
+			continue;
+
+		joinrelids = bms_union(rel->relids, removalrel->relids);
+
+		/* if any of the Vars from the relation are needed then abort */
+		if (relation_is_needed(root, joinrelids, removalrel, ignoredrels))
+			return false;
+
+		referencing_vars = NIL;
+		index_vars = NIL;
+		operator_list = NIL;
+
+		/* now populate the lists with the join condition Vars */
+		foreach(lc2, root->eq_classes)
+		{
+			EquivalenceClass *ec = (EquivalenceClass *) lfirst(lc2);
+
+			if (list_length(ec->ec_members) <= 1)
+				continue;
+
+			if (bms_overlap(removalrel->relids, ec->ec_relids) &&
+				bms_overlap(rel->relids, ec->ec_relids))
+			{
+				ListCell *lc3;
+				Var *refvar = NULL;
+				Var *idxvar = NULL;
+
+				/*
+				 * Look at each member of the eclass and try to find a Var from
+				 * each side of the join that we can append to the list of
+				 * columns that should be checked against each foreign key.
+				 *
+				 * The following logic does not allow for join removals to take
+				 * place for foreign keys that have duplicate columns on the
+				 * referencing side of the foreign key, such as:
+				 * (a,a) references (x,y)
+				 * The use case for such a foreign key is likely small enough
+				 * that we needn't bother making this code anymore complex to
+				 * solve. If we find more than 1 Var from any of the rels then
+				 * we'll bail out.
+				 */
+				foreach (lc3, ec->ec_members)
+				{
+					EquivalenceMember *ecm = (EquivalenceMember *) lfirst(lc3);
+
+					Var *var = (Var *) ecm->em_expr;
+
+					if (!IsA(var, Var))
+						continue; /* Ignore Consts */
+
+					if (var->varno == rel->relid)
+					{
+						if (refvar != NULL)
+							return false;
+						refvar = var;
+					}
+
+					else if (var->varno == removalrel->relid)
+					{
+						if (idxvar != NULL)
+							return false;
+						idxvar = var;
+					}
+				}
+
+				if (refvar != NULL && idxvar != NULL)
+				{
+					Oid opno;
+					Oid reloid = root->simple_rte_array[refvar->varno]->relid;
+
+					if (!get_attnotnull(reloid, refvar->varattno))
+						return false;
+
+					/* grab the correct equality operator for these two vars */
+					opno = select_equality_operator(ec, refvar->vartype, idxvar->vartype);
+
+					if (!OidIsValid(opno))
+						return false;
+
+					referencing_vars = lappend(referencing_vars, refvar);
+					index_vars = lappend(index_vars, idxvar);
+					operator_list = lappend_oid(operator_list, opno);
+				}
+			}
+		}
+
+		if (referencing_vars != NULL)
+		{
+			if (relation_has_foreign_key_for(root, rel, removalrel,
+				referencing_vars, index_vars, operator_list))
+				return true; /* removalrel can be removed */
+		}
+	}
+
+	return false; /* can't remove join */
+}
+
+/*
+ * leftjoin_is_removable
+ *	  Check whether we need not perform this left join at all, because
  *	  it will just duplicate its left input.
  *
  * This is true for a left join for which the join condition cannot match
@@ -147,7 +424,7 @@ clause_sides_match_join(RestrictInfo *rinfo, Relids outerrelids,
  * above the join.
  */
 static bool
-join_is_removable(PlannerInfo *root, SpecialJoinInfo *sjinfo)
+leftjoin_is_removable(PlannerInfo *root, SpecialJoinInfo *sjinfo)
 {
 	int			innerrelid;
 	RelOptInfo *innerrel;
@@ -155,14 +432,14 @@ join_is_removable(PlannerInfo *root, SpecialJoinInfo *sjinfo)
 	Relids		joinrelids;
 	List	   *clause_list = NIL;
 	ListCell   *l;
-	int			attroff;
+
+	Assert(sjinfo->jointype == JOIN_LEFT);
 
 	/*
-	 * Must be a non-delaying left join to a single baserel, else we aren't
+	 * Must be a non-delaying join to a single baserel, else we aren't
 	 * going to be able to do anything with it.
 	 */
-	if (sjinfo->jointype != JOIN_LEFT ||
-		sjinfo->delay_upper_joins ||
+	if (sjinfo->delay_upper_joins ||
 		bms_membership(sjinfo->min_righthand) != BMS_SINGLETON)
 		return false;
 
@@ -205,52 +482,9 @@ join_is_removable(PlannerInfo *root, SpecialJoinInfo *sjinfo)
 	/* Compute the relid set for the join we are considering */
 	joinrelids = bms_union(sjinfo->min_lefthand, sjinfo->min_righthand);
 
-	/*
-	 * We can't remove the join if any inner-rel attributes are used above the
-	 * join.
-	 *
-	 * Note that this test only detects use of inner-rel attributes in higher
-	 * join conditions and the target list.  There might be such attributes in
-	 * pushed-down conditions at this join, too.  We check that case below.
-	 *
-	 * As a micro-optimization, it seems better to start with max_attr and
-	 * count down rather than starting with min_attr and counting up, on the
-	 * theory that the system attributes are somewhat less likely to be wanted
-	 * and should be tested last.
-	 */
-	for (attroff = innerrel->max_attr - innerrel->min_attr;
-		 attroff >= 0;
-		 attroff--)
-	{
-		if (!bms_is_subset(innerrel->attr_needed[attroff], joinrelids))
-			return false;
-	}
-
-	/*
-	 * Similarly check that the inner rel isn't needed by any PlaceHolderVars
-	 * that will be used above the join.  We only need to fail if such a PHV
-	 * actually references some inner-rel attributes; but the correct check
-	 * for that is relatively expensive, so we first check against ph_eval_at,
-	 * which must mention the inner rel if the PHV uses any inner-rel attrs as
-	 * non-lateral references.  Note that if the PHV's syntactic scope is just
-	 * the inner rel, we can't drop the rel even if the PHV is variable-free.
-	 */
-	foreach(l, root->placeholder_list)
-	{
-		PlaceHolderInfo *phinfo = (PlaceHolderInfo *) lfirst(l);
-
-		if (bms_is_subset(phinfo->ph_needed, joinrelids))
-			continue;			/* PHV is not used above the join */
-		if (bms_overlap(phinfo->ph_lateral, innerrel->relids))
-			return false;		/* it references innerrel laterally */
-		if (!bms_overlap(phinfo->ph_eval_at, innerrel->relids))
-			continue;			/* it definitely doesn't reference innerrel */
-		if (bms_is_subset(phinfo->ph_eval_at, innerrel->relids))
-			return false;		/* there isn't any other place to eval PHV */
-		if (bms_overlap(pull_varnos((Node *) phinfo->ph_var->phexpr),
-						innerrel->relids))
-			return false;		/* it does reference innerrel */
-	}
+	/* if the relation is referenced in the query then it cannot be removed */
+	if (relation_is_needed(root, joinrelids, innerrel, NULL))
+		return false;
 
 	/*
 	 * Search for mergejoinable clauses that constrain the inner rel against
@@ -367,6 +601,218 @@ join_is_removable(PlannerInfo *root, SpecialJoinInfo *sjinfo)
 	return false;
 }
 
+/*
+ * relation_is_needed
+ *		True if any of the Vars from this relation are required in the query
+ */
+static inline bool
+relation_is_needed(PlannerInfo *root, Relids joinrelids, RelOptInfo *rel, Relids ignoredrels)
+{
+	int		  attroff;
+	ListCell *l;
+
+	/*
+	 * rel is referenced if any of it's attributes are used above the join.
+	 *
+	 * Note that this test only detects use of rel's attributes in higher
+	 * join conditions and the target list.  There might be such attributes in
+	 * pushed-down conditions at this join, too.  We check that case below.
+	 *
+	 * As a micro-optimization, it seems better to start with max_attr and
+	 * count down rather than starting with min_attr and counting up, on the
+	 * theory that the system attributes are somewhat less likely to be wanted
+	 * and should be tested last.
+	 */
+	for (attroff = rel->max_attr - rel->min_attr;
+		 attroff >= 0;
+		 attroff--)
+	{
+		if (!bms_is_subset(bms_difference(rel->attr_needed[attroff], ignoredrels), joinrelids))
+			return true;
+	}
+
+	/*
+	 * Similarly check that rel isn't needed by any PlaceHolderVars that will
+	 * be used above the join.  We only need to fail if such a PHV actually
+	 * references some of rel's attributes; but the correct check for that is
+	 * relatively expensive, so we first check against ph_eval_at, which must
+	 * mention rel if the PHV uses any of-rel's attrs as non-lateral
+	 * references.  Note that if the PHV's syntactic scope is just rel, we
+	 * can't return true even if the PHV is variable-free.
+	 */
+	foreach(l, root->placeholder_list)
+	{
+		PlaceHolderInfo *phinfo = (PlaceHolderInfo *) lfirst(l);
+
+		if (bms_is_subset(phinfo->ph_needed, joinrelids))
+			continue;			/* PHV is not used above the join */
+		if (bms_overlap(phinfo->ph_lateral, rel->relids))
+			return true;		/* it references rel laterally */
+		if (!bms_overlap(phinfo->ph_eval_at, rel->relids))
+			continue;			/* it definitely doesn't reference rel */
+		if (bms_is_subset(phinfo->ph_eval_at, rel->relids))
+			return true;		/* there isn't any other place to eval PHV */
+		if (bms_overlap(pull_varnos((Node *) phinfo->ph_var->phexpr),
+						rel->relids))
+			return true;		/* it does reference rel */
+	}
+
+	return false; /* it does not reference rel */
+}
+
+/*
+ * relation_has_foreign_key_for
+ *	  Checks if rel has a foreign key which references referencedrel with the
+ *	  given list of expressions.
+ *
+ *	For the match to succeed:
+ *	  referencing_vars must match the columns defined in the foreign key.
+ *	  index_vars must match the columns defined in the index for the foreign key.
+ */
+static bool
+relation_has_foreign_key_for(PlannerInfo *root, RelOptInfo *rel,
+			RelOptInfo *referencedrel, List *referencing_vars,
+			List *index_vars, List *operator_list)
+{
+	ListCell *lc;
+	Oid		  refreloid;
+
+	/*
+	 * Look up the Oid of the referenced relation. We only want to look at
+	 * foreign keys on the referencing relation which reference this relation.
+	 */
+	refreloid = root->simple_rte_array[referencedrel->relid]->relid;
+
+	Assert(list_length(referencing_vars) > 0);
+	Assert(list_length(referencing_vars) == list_length(index_vars));
+	Assert(list_length(referencing_vars) == list_length(operator_list));
+
+	/*
+	 * Search through each foreign key on the referencing relation and try
+	 * to find one which references the relation in the join condition. If we
+	 * find one then we'll send the join conditions off to
+	 * expressions_match_foreign_key() to see if they match the foreign key.
+	 */
+	foreach(lc, rel->fklist)
+	{
+		ForeignKeyInfo *fk = (ForeignKeyInfo *) lfirst(lc);
+
+		if (fk->confrelid == refreloid)
+		{
+			if (expressions_match_foreign_key(fk, referencing_vars,
+				index_vars, operator_list))
+				return true;
+		}
+	}
+
+	return false;
+}
+
+/*
+ * expressions_match_foreign_key
+ *		True if the given fkvars, indexvars and operators will match
+ *		exactly 1 record in the referenced relation of the foreign key.
+ *
+ * Note: This function expects fkvars and indexvars to only contain Var types.
+ *		 Expression indexes are not supported by foreign keys.
+ */
+static bool
+expressions_match_foreign_key(ForeignKeyInfo *fk, List *fkvars,
+					List *indexvars, List *operators)
+{
+	ListCell  *lc;
+	ListCell  *lc2;
+	ListCell  *lc3;
+	Bitmapset *allitems;
+	Bitmapset *matcheditems;
+	int		   lstidx;
+	int		   col;
+
+	Assert(list_length(fkvars) == list_length(indexvars));
+	Assert(list_length(fkvars) == list_length(operators));
+
+	/*
+	 * Fast path out if there's not enough conditions to match each column in
+	 * the foreign key. Note that we cannot check that the number of
+	 * expressions are equal here since it would cause any expressions which
+	 * are duplicated not to match.
+	 */
+	if (list_length(fkvars) < fk->conncols)
+		return false;
+
+	/*
+	 * We need to ensure that each foreign key column can be matched to a list
+	 * item, and we need to ensure that each list item can be matched to a
+	 * foreign key column. We do this by looping over each foreign key column
+	 * and checking that we can find an item in the list which matches the
+	 * current column, however this method does not allow us to ensure that no
+	 * additional items exist in the list. We could solve that by performing
+	 * another loop over each list item and check that it matches a foreign key
+	 * column, but that's a bit wasteful. Instead we'll use 2 bitmapsets, one
+	 * to store the 0 based index of each list item, and with the other we'll
+	 * store each list index that we've managed to match. After we're done
+	 * matching we'll just make sure that both bitmapsets are equal.
+	 */
+	allitems = NULL;
+	matcheditems = NULL;
+
+	/*
+	 * Build a bitmapset which contains each 1 based list index. It seems more
+	 * efficient to do this in reverse so that we allocate enough memory for
+	 * the bitmapset on first loop rather than reallocating each time we find
+	 * we need a bit more space.
+	 */
+	for (lstidx = list_length(fkvars) - 1; lstidx >= 0; lstidx--)
+		allitems = bms_add_member(allitems, lstidx);
+
+	for (col = 0; col < fk->conncols; col++)
+	{
+		bool  matched = false;
+
+		lstidx = 0;
+
+		forthree(lc, fkvars, lc2, indexvars, lc3, operators)
+		{
+			Var *expr = (Var *) lfirst(lc);
+			Var *idxexpr = (Var *) lfirst(lc2);
+			Oid  opr = lfirst_oid(lc3);
+
+			Assert(IsA(expr, Var));
+			Assert(IsA(idxexpr, Var));
+
+			/* Does this join qual match up to the current fkey column? */
+			if (fk->conkey[col] == expr->varattno &&
+				fk->confkey[col] == idxexpr->varattno &&
+				equality_ops_are_compatible(opr, fk->conpfeqop[col]))
+			{
+				matched = true;
+
+				/* mark this list item as matched */
+				matcheditems = bms_add_member(matcheditems, lstidx);
+
+				/*
+				 * Don't break here as there may be duplicate expressions
+				 * that we also need to match against.
+				 */
+			}
+			lstidx++;
+		}
+
+		/* punt if there's no match. */
+		if (!matched)
+			return false;
+	}
+
+	/*
+	 * Ensure that we managed to match every item in the list to a foreign key
+	 * column.
+	 */
+	if (!bms_equal(allitems, matcheditems))
+		return false;
+
+	return true; /* matched */
+}
+
 
 /*
  * Remove the target relid from the planner's data structures, having
diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
index fb74d6b..7ea0149 100644
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -3712,6 +3712,7 @@ plan_cluster_use_sort(Oid tableOid, Oid indexOid)
 	rte->lateral = false;
 	rte->inh = false;
 	rte->inFromCl = true;
+	rte->skipJoinPossible = false;
 	query->rtable = list_make1(rte);
 
 	/* Set up RTE/RelOptInfo arrays */
diff --git a/src/backend/optimizer/prep/prepsecurity.c b/src/backend/optimizer/prep/prepsecurity.c
index b625b5c..74a0dca 100644
--- a/src/backend/optimizer/prep/prepsecurity.c
+++ b/src/backend/optimizer/prep/prepsecurity.c
@@ -311,6 +311,7 @@ expand_security_qual(PlannerInfo *root, List *tlist, int rt_index,
 			subrte->security_barrier = rte->security_barrier;
 			subrte->eref = copyObject(rte->eref);
 			subrte->inFromCl = true;
+			subrte->skipJoinPossible = false;
 			subquery->rtable = list_make1(subrte);
 
 			subrtr = makeNode(RangeTblRef);
diff --git a/src/backend/optimizer/util/plancat.c b/src/backend/optimizer/util/plancat.c
index b2becfa..fea198e 100644
--- a/src/backend/optimizer/util/plancat.c
+++ b/src/backend/optimizer/util/plancat.c
@@ -25,7 +25,9 @@
 #include "access/transam.h"
 #include "access/xlog.h"
 #include "catalog/catalog.h"
+#include "catalog/pg_constraint.h"
 #include "catalog/heap.h"
+#include "catalog/pg_type.h"
 #include "foreign/fdwapi.h"
 #include "miscadmin.h"
 #include "nodes/makefuncs.h"
@@ -38,6 +40,7 @@
 #include "parser/parsetree.h"
 #include "rewrite/rewriteManip.h"
 #include "storage/bufmgr.h"
+#include "utils/fmgroids.h"
 #include "utils/lsyscache.h"
 #include "utils/rel.h"
 #include "utils/snapmgr.h"
@@ -89,6 +92,12 @@ get_relation_info(PlannerInfo *root, Oid relationObjectId, bool inhparent,
 	Relation	relation;
 	bool		hasindex;
 	List	   *indexinfos = NIL;
+	List	   *fkinfos = NIL;
+	Relation	fkeyRel;
+	Relation	fkeyRelIdx;
+	ScanKeyData fkeyScankey;
+	SysScanDesc fkeyScan;
+	HeapTuple	tuple;
 
 	/*
 	 * We need not lock the relation since it was already locked, either by
@@ -384,6 +393,111 @@ get_relation_info(PlannerInfo *root, Oid relationObjectId, bool inhparent,
 
 	heap_close(relation, NoLock);
 
+	/* load foreign key constraints */
+	ScanKeyInit(&fkeyScankey,
+				Anum_pg_constraint_conrelid,
+				BTEqualStrategyNumber, F_OIDEQ,
+				ObjectIdGetDatum(relationObjectId));
+
+	fkeyRel = heap_open(ConstraintRelationId, AccessShareLock);
+	fkeyRelIdx = index_open(ConstraintRelidIndexId, AccessShareLock);
+	fkeyScan = systable_beginscan_ordered(fkeyRel, fkeyRelIdx, NULL, 1, &fkeyScankey);
+
+	while ((tuple = systable_getnext_ordered(fkeyScan, ForwardScanDirection)) != NULL)
+	{
+		Form_pg_constraint con = (Form_pg_constraint) GETSTRUCT(tuple);
+		ForeignKeyInfo *fkinfo;
+		Datum		adatum;
+		bool		isNull;
+		ArrayType  *arr;
+		int			nelements;
+
+		/* skip if not a foreign key */
+		if (con->contype != CONSTRAINT_FOREIGN)
+			continue;
+
+		/* we're not interested unless the fkey has been validated */
+		if (!con->convalidated)
+			continue;
+
+		fkinfo = (ForeignKeyInfo *) palloc(sizeof(ForeignKeyInfo));
+		fkinfo->conindid = con->conindid;
+		fkinfo->confrelid = con->confrelid;
+		fkinfo->convalidated = con->convalidated;
+		fkinfo->conrelid = con->conrelid;
+		fkinfo->confupdtype = con->confupdtype;
+		fkinfo->confdeltype = con->confdeltype;
+		fkinfo->confmatchtype = con->confmatchtype;
+
+		adatum = heap_getattr(tuple, Anum_pg_constraint_conkey,
+							RelationGetDescr(fkeyRel), &isNull);
+
+		if (isNull)
+			elog(ERROR, "null conkey for constraint %u",
+				HeapTupleGetOid(tuple));
+
+		arr = DatumGetArrayTypeP(adatum);		/* ensure not toasted */
+		nelements = ARR_DIMS(arr)[0];
+		if (ARR_NDIM(arr) != 1 ||
+			nelements < 0 ||
+			ARR_HASNULL(arr) ||
+			ARR_ELEMTYPE(arr) != INT2OID)
+			elog(ERROR, "conkey is not a 1-D smallint array");
+
+		fkinfo->conkey = (int16 *) ARR_DATA_PTR(arr);
+		fkinfo->conncols = nelements;
+
+		adatum = heap_getattr(tuple, Anum_pg_constraint_confkey,
+							RelationGetDescr(fkeyRel), &isNull);
+
+		if (isNull)
+			elog(ERROR, "null confkey for constraint %u",
+				HeapTupleGetOid(tuple));
+
+		arr = DatumGetArrayTypeP(adatum);		/* ensure not toasted */
+		nelements = ARR_DIMS(arr)[0];
+
+		if (ARR_NDIM(arr) != 1 ||
+			nelements < 0 ||
+			ARR_HASNULL(arr) ||
+			ARR_ELEMTYPE(arr) != INT2OID)
+			elog(ERROR, "confkey is not a 1-D smallint array");
+
+		/* sanity check */
+		if (nelements != fkinfo->conncols)
+			elog(ERROR, "number of confkey elements does not equal conkey elements");
+
+		fkinfo->confkey = (int16 *) ARR_DATA_PTR(arr);
+		adatum = heap_getattr(tuple, Anum_pg_constraint_conpfeqop,
+							RelationGetDescr(fkeyRel), &isNull);
+
+		if (isNull)
+			elog(ERROR, "null conpfeqop for constraint %u",
+				HeapTupleGetOid(tuple));
+
+		arr = DatumGetArrayTypeP(adatum);		/* ensure not toasted */
+		nelements = ARR_DIMS(arr)[0];
+
+		if (ARR_NDIM(arr) != 1 ||
+			nelements < 0 ||
+			ARR_HASNULL(arr) ||
+			ARR_ELEMTYPE(arr) != OIDOID)
+			elog(ERROR, "conpfeqop is not a 1-D smallint array");
+
+		/* sanity check */
+		if (nelements != fkinfo->conncols)
+			elog(ERROR, "number of conpfeqop elements does not equal conkey elements");
+
+		fkinfo->conpfeqop = (Oid *) ARR_DATA_PTR(arr);
+
+		fkinfos = lappend(fkinfos, fkinfo);
+	}
+
+	rel->fklist = fkinfos;
+	systable_endscan_ordered(fkeyScan);
+	index_close(fkeyRelIdx, AccessShareLock);
+	heap_close(fkeyRel, AccessShareLock);
+
 	/*
 	 * Allow a plugin to editorialize on the info we obtained from the
 	 * catalogs.  Actions might include altering the assumed relation size,
diff --git a/src/backend/optimizer/util/relnode.c b/src/backend/optimizer/util/relnode.c
index 4c76f54..58d80bb 100644
--- a/src/backend/optimizer/util/relnode.c
+++ b/src/backend/optimizer/util/relnode.c
@@ -115,6 +115,7 @@ build_simple_rel(PlannerInfo *root, int relid, RelOptKind reloptkind)
 	rel->lateral_relids = NULL;
 	rel->lateral_referencers = NULL;
 	rel->indexlist = NIL;
+	rel->fklist = NIL;
 	rel->pages = 0;
 	rel->tuples = 0;
 	rel->allvisfrac = 0;
@@ -377,6 +378,7 @@ build_join_rel(PlannerInfo *root,
 	joinrel->lateral_relids = NULL;
 	joinrel->lateral_referencers = NULL;
 	joinrel->indexlist = NIL;
+	joinrel->fklist = NIL;
 	joinrel->pages = 0;
 	joinrel->tuples = 0;
 	joinrel->allvisfrac = 0;
diff --git a/src/backend/parser/parse_relation.c b/src/backend/parser/parse_relation.c
index 478584d..cafeba9 100644
--- a/src/backend/parser/parse_relation.c
+++ b/src/backend/parser/parse_relation.c
@@ -1048,6 +1048,7 @@ addRangeTableEntry(ParseState *pstate,
 	rte->lateral = false;
 	rte->inh = inh;
 	rte->inFromCl = inFromCl;
+	rte->skipJoinPossible = false;
 
 	rte->requiredPerms = ACL_SELECT;
 	rte->checkAsUser = InvalidOid;		/* not set-uid by default, either */
@@ -1101,6 +1102,7 @@ addRangeTableEntryForRelation(ParseState *pstate,
 	rte->lateral = false;
 	rte->inh = inh;
 	rte->inFromCl = inFromCl;
+	rte->skipJoinPossible = false;
 
 	rte->requiredPerms = ACL_SELECT;
 	rte->checkAsUser = InvalidOid;		/* not set-uid by default, either */
@@ -1179,6 +1181,7 @@ addRangeTableEntryForSubquery(ParseState *pstate,
 	rte->lateral = lateral;
 	rte->inh = false;			/* never true for subqueries */
 	rte->inFromCl = inFromCl;
+	rte->skipJoinPossible = false;
 
 	rte->requiredPerms = 0;
 	rte->checkAsUser = InvalidOid;
@@ -1433,6 +1436,7 @@ addRangeTableEntryForFunction(ParseState *pstate,
 	rte->lateral = lateral;
 	rte->inh = false;			/* never true for functions */
 	rte->inFromCl = inFromCl;
+	rte->skipJoinPossible = false;
 
 	rte->requiredPerms = 0;
 	rte->checkAsUser = InvalidOid;
@@ -1505,6 +1509,7 @@ addRangeTableEntryForValues(ParseState *pstate,
 	rte->lateral = lateral;
 	rte->inh = false;			/* never true for values RTEs */
 	rte->inFromCl = inFromCl;
+	rte->skipJoinPossible = false;
 
 	rte->requiredPerms = 0;
 	rte->checkAsUser = InvalidOid;
@@ -1573,6 +1578,7 @@ addRangeTableEntryForJoin(ParseState *pstate,
 	rte->lateral = false;
 	rte->inh = false;			/* never true for joins */
 	rte->inFromCl = inFromCl;
+	rte->skipJoinPossible = false;
 
 	rte->requiredPerms = 0;
 	rte->checkAsUser = InvalidOid;
@@ -1673,6 +1679,7 @@ addRangeTableEntryForCTE(ParseState *pstate,
 	rte->lateral = false;
 	rte->inh = false;			/* never true for subqueries */
 	rte->inFromCl = inFromCl;
+	rte->skipJoinPossible = false;
 
 	rte->requiredPerms = 0;
 	rte->checkAsUser = InvalidOid;
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index bf4e81f..919a3b2 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -843,6 +843,7 @@ pg_get_triggerdef_worker(Oid trigid, bool pretty)
 		oldrte->lateral = false;
 		oldrte->inh = false;
 		oldrte->inFromCl = true;
+		oldrte->skipJoinPossible = false;
 
 		newrte = makeNode(RangeTblEntry);
 		newrte->rtekind = RTE_RELATION;
@@ -853,6 +854,7 @@ pg_get_triggerdef_worker(Oid trigid, bool pretty)
 		newrte->lateral = false;
 		newrte->inh = false;
 		newrte->inFromCl = true;
+		newrte->skipJoinPossible = false;
 
 		/* Build two-element rtable */
 		memset(&dpns, 0, sizeof(dpns));
@@ -2508,6 +2510,7 @@ deparse_context_for(const char *aliasname, Oid relid)
 	rte->lateral = false;
 	rte->inh = false;
 	rte->inFromCl = true;
+	rte->skipJoinPossible = false;
 
 	/* Build one-element rtable */
 	dpns->rtable = list_make1(rte);
diff --git a/src/backend/utils/cache/lsyscache.c b/src/backend/utils/cache/lsyscache.c
index 552e498..aa81c7c 100644
--- a/src/backend/utils/cache/lsyscache.c
+++ b/src/backend/utils/cache/lsyscache.c
@@ -916,6 +916,33 @@ get_atttypetypmodcoll(Oid relid, AttrNumber attnum,
 	ReleaseSysCache(tp);
 }
 
+/*
+ * get_attnotnull
+ *
+ *		Given the relation id and the attribute number,
+ *		return the "attnotnull" field from the attribute relation.
+ */
+bool
+get_attnotnull(Oid relid, AttrNumber attnum)
+{
+	HeapTuple	tp;
+
+	tp = SearchSysCache2(ATTNUM,
+						 ObjectIdGetDatum(relid),
+						 Int16GetDatum(attnum));
+	if (HeapTupleIsValid(tp))
+	{
+		Form_pg_attribute att_tup = (Form_pg_attribute) GETSTRUCT(tp);
+		bool		result;
+
+		result = att_tup->attnotnull;
+		ReleaseSysCache(tp);
+		return result;
+	}
+	else
+		return false;
+}
+
 /*				---------- COLLATION CACHE ----------					 */
 
 /*
diff --git a/src/include/commands/trigger.h b/src/include/commands/trigger.h
index d0b0356..34a75e4 100644
--- a/src/include/commands/trigger.h
+++ b/src/include/commands/trigger.h
@@ -181,6 +181,7 @@ extern void ExecBSTruncateTriggers(EState *estate,
 extern void ExecASTruncateTriggers(EState *estate,
 					   ResultRelInfo *relinfo);
 
+extern bool AfterTriggerQueueIsEmpty(void);
 extern void AfterTriggerBeginXact(void);
 extern void AfterTriggerBeginQuery(void);
 extern void AfterTriggerEndQuery(EState *estate);
diff --git a/src/include/executor/executor.h b/src/include/executor/executor.h
index f1b65b4..2a0c0f6 100644
--- a/src/include/executor/executor.h
+++ b/src/include/executor/executor.h
@@ -65,6 +65,15 @@
 #define EXEC_FLAG_WITHOUT_OIDS	0x0040	/* force no OIDs in returned tuples */
 #define EXEC_FLAG_WITH_NO_DATA	0x0080	/* rel scannability doesn't matter */
 
+/* Flags used for JoinState.skipflags */
+#define EXEC_SKIPJOIN_INNER		0x0001 /* Skip inner side of join */
+#define EXEC_SKIPJOIN_OUTER		0x0002 /* Skip outer side of join */
+#define EXEC_SKIPJOIN_BOTH		(EXEC_SKIPJOIN_OUTER|EXEC_SKIPJOIN_INNER)
+
+#define HasFlagSkipJoinInner(n)	((n) & EXEC_SKIPJOIN_INNER)
+#define HasFlagSkipJoinOuter(n)	((n) & EXEC_SKIPJOIN_OUTER)
+#define HasFlagSkipJoinBoth(n)	((n) & EXEC_SKIPJOIN_BOTH) == EXEC_SKIPJOIN_BOTH
+#define HasFlagSkipJoinAny(n)	((n) != 0)
 
 /*
  * ExecEvalExpr was formerly a function containing a switch statement;
@@ -339,6 +348,7 @@ extern ProjectionInfo *ExecBuildProjectionInfo(List *targetList,
 						ExprContext *econtext,
 						TupleTableSlot *slot,
 						TupleDesc inputDesc);
+extern bool ExecCanSkipJoin(PlanState *planstate);
 extern void ExecAssignProjectionInfo(PlanState *planstate,
 						 TupleDesc inputDesc);
 extern void ExecFreeExprContext(PlanState *planstate);
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index 8c8c01f..6403149 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -1561,6 +1561,7 @@ typedef struct JoinState
 	PlanState	ps;
 	JoinType	jointype;
 	List	   *joinqual;		/* JOIN quals (in addition to ps.qual) */
+	int			skipflags;
 } JoinState;
 
 /* ----------------
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 3e4f815..7f74202 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -813,6 +813,8 @@ typedef struct RangeTblEntry
 	bool		lateral;		/* subquery, function, or values is LATERAL? */
 	bool		inh;			/* inheritance requested? */
 	bool		inFromCl;		/* present in FROM clause? */
+	bool		skipJoinPossible; /* it may be possible to not bother joining
+								   * this relation at all */
 	AclMode		requiredPerms;	/* bitmask of required access permissions */
 	Oid			checkAsUser;	/* if valid, check access as this role */
 	Bitmapset  *selectedCols;	/* columns needing SELECT permission */
diff --git a/src/include/nodes/relation.h b/src/include/nodes/relation.h
index 05cfbcd..4a1bf47 100644
--- a/src/include/nodes/relation.h
+++ b/src/include/nodes/relation.h
@@ -359,6 +359,8 @@ typedef struct PlannerInfo
  *		lateral_referencers - relids of rels that reference this one laterally
  *		indexlist - list of IndexOptInfo nodes for relation's indexes
  *					(always NIL if it's not a table)
+ *		fklist - list of ForeignKeyInfo's for relation's foreign key
+ *					constraints. (always NIL if it's not a table)
  *		pages - number of disk pages in relation (zero if not a table)
  *		tuples - number of tuples in relation (not considering restrictions)
  *		allvisfrac - fraction of disk pages that are marked all-visible
@@ -452,6 +454,7 @@ typedef struct RelOptInfo
 	Relids		lateral_relids; /* minimum parameterization of rel */
 	Relids		lateral_referencers;	/* rels that reference me laterally */
 	List	   *indexlist;		/* list of IndexOptInfo */
+	List	   *fklist;			/* list of ForeignKeyInfo */
 	BlockNumber pages;			/* size estimates derived from pg_class */
 	double		tuples;
 	double		allvisfrac;
@@ -542,6 +545,51 @@ typedef struct IndexOptInfo
 	bool		amhasgetbitmap; /* does AM have amgetbitmap interface? */
 } IndexOptInfo;
 
+/*
+ * ForeignKeyInfo
+ *		Used to store pg_constraint records for foreign key constraints for use
+ *		by the planner.
+ *
+ *		conindid - The index which supports the foreign key
+ *
+ *		confrelid - The relation that is referenced by this foreign key
+ *
+ *		convalidated - True if the foreign key has been validated.
+ *
+ *		conrelid - The Oid of the relation that the foreign key belongs to
+ *
+ *		confupdtype - ON UPDATE action for when the referenced table is updated
+ *
+ *		confdeltype - ON DELETE action, controls what to do when a record is
+ *					deleted from the referenced table.
+ *
+ *		confmatchtype - foreign key match type, e.g MATCH FULL, MATCH PARTIAL
+ *
+ *		conncols - Number of columns defined in the foreign key
+ *
+ *		conkey - An array of conncols elements to store the varattno of the
+ *					columns on the referencing side of the foreign key
+ *
+ *		confkey - An array of conncols elements to store the varattno of the
+ *					columns on the referenced side of the foreign key
+ *
+ *		conpfeqop - An array of conncols elements to store the operators for
+ *					PK = FK comparisons
+ */
+typedef struct ForeignKeyInfo
+{
+	Oid			conindid;		/* index supporting this constraint */
+	Oid			confrelid;		/* relation referenced by foreign key */
+	bool		convalidated;	/* constraint has been validated? */
+	Oid			conrelid;		/* relation this constraint constrains */
+	char		confupdtype;	/* foreign key's ON UPDATE action */
+	char		confdeltype;	/* foreign key's ON DELETE action */
+	char		confmatchtype;	/* foreign key's match type */
+	int			conncols;		/* number of columns references */
+	int16	   *conkey;			/* Columns of conrelid that the constraint applies to */
+	int16	   *confkey;		/* columns of confrelid that foreign key references */
+	Oid		   *conpfeqop;		/* Operator list for comparing PK to FK */
+} ForeignKeyInfo;
 
 /*
  * EquivalenceClasses
diff --git a/src/include/optimizer/paths.h b/src/include/optimizer/paths.h
index 9b22fda..b11ae78 100644
--- a/src/include/optimizer/paths.h
+++ b/src/include/optimizer/paths.h
@@ -108,10 +108,13 @@ extern EquivalenceClass *get_eclass_for_sort_expr(PlannerInfo *root,
 						 Relids rel,
 						 bool create_it);
 extern void generate_base_implied_equalities(PlannerInfo *root);
+extern void remove_rel_from_eclass(PlannerInfo *root, int relid);
 extern List *generate_join_implied_equalities(PlannerInfo *root,
 								 Relids join_relids,
 								 Relids outer_relids,
 								 RelOptInfo *inner_rel);
+extern Oid select_equality_operator(EquivalenceClass *ec, Oid lefttype,
+								 Oid righttype);
 extern bool exprs_known_equal(PlannerInfo *root, Node *item1, Node *item2);
 extern void add_child_rel_equivalences(PlannerInfo *root,
 						   AppendRelInfo *appinfo,
diff --git a/src/include/utils/lsyscache.h b/src/include/utils/lsyscache.h
index 07d24d4..910190d 100644
--- a/src/include/utils/lsyscache.h
+++ b/src/include/utils/lsyscache.h
@@ -68,6 +68,7 @@ extern Oid	get_atttype(Oid relid, AttrNumber attnum);
 extern int32 get_atttypmod(Oid relid, AttrNumber attnum);
 extern void get_atttypetypmodcoll(Oid relid, AttrNumber attnum,
 					  Oid *typid, int32 *typmod, Oid *collid);
+extern bool get_attnotnull(Oid relid, AttrNumber attnum);
 extern char *get_collation_name(Oid colloid);
 extern char *get_constraint_name(Oid conoid);
 extern Oid	get_opclass_family(Oid opclass);
diff --git a/src/test/regress/expected/join.out b/src/test/regress/expected/join.out
index 2501184..4299227 100644
--- a/src/test/regress/expected/join.out
+++ b/src/test/regress/expected/join.out
@@ -3276,6 +3276,32 @@ select i8.* from int8_tbl i8 left join (select f1 from int4_tbl group by f1) i4
 (1 row)
 
 rollback;
+begin work;
+create temp table c (
+  id int primary key
+);
+create temp table b (
+  id int primary key,
+  c_id int not null,
+  constraint b_c_id_fkey foreign key (c_id) references c deferrable
+);
+create temp table a (
+  id int primary key,
+  b_id int not null,
+  constraint a_b_id_fkey foreign key (b_id) references b deferrable
+);
+insert into c (id) values(1);
+insert into b (id, c_id) values(1,1);
+insert into a (id, b_id) values(1,1);
+set constraints b_c_id_fkey deferred;
+update c set id = 2 where id=1;
+-- ensure inner join to be is not skipped.
+select b.* from b inner join c on b.c_id = c.id;
+ id | c_id 
+----+------
+(0 rows)
+
+rollback;
 create temp table parent (k int primary key, pd int);
 create temp table child (k int unique, cd int);
 insert into parent values (1, 10), (2, 20), (3, 30);
diff --git a/src/test/regress/sql/join.sql b/src/test/regress/sql/join.sql
index 718e1d9..e226e4e 100644
--- a/src/test/regress/sql/join.sql
+++ b/src/test/regress/sql/join.sql
@@ -977,6 +977,34 @@ select i8.* from int8_tbl i8 left join (select f1 from int4_tbl group by f1) i4
 
 rollback;
 
+begin work;
+
+create temp table c (
+  id int primary key
+);
+create temp table b (
+  id int primary key,
+  c_id int not null,
+  constraint b_c_id_fkey foreign key (c_id) references c deferrable
+);
+create temp table a (
+  id int primary key,
+  b_id int not null,
+  constraint a_b_id_fkey foreign key (b_id) references b deferrable
+);
+
+insert into c (id) values(1);
+insert into b (id, c_id) values(1,1);
+insert into a (id, b_id) values(1,1);
+
+set constraints b_c_id_fkey deferred;
+update c set id = 2 where id=1;
+
+-- ensure inner join to be is not skipped.
+select b.* from b inner join c on b.c_id = c.id;
+
+rollback;
+
 create temp table parent (k int primary key, pd int);
 create temp table child (k int unique, cd int);
 insert into parent values (1, 10), (2, 20), (3, 30);