Add Assert that will crash before coercion fix is in

src/backend/distributed/planner/shard_pruning.c

@@ -63,6 +63,7 @@
 #include "nodes/nodeFuncs.h"
 #include "nodes/makefuncs.h"
 #include "optimizer/clauses.h"
+#include "parser/parse_coerce.h"
 #include "utils/arrayaccess.h"
 #include "utils/catcache.h"
 #include "utils/lsyscache.h"
@@ -715,13 +716,15 @@ AddNewConjuction(ClauseWalkerContext *context, OpExpr *op)
  */
 static void
 AddPartitionKeyRestrictionToInstance(ClauseWalkerContext *context, OpExpr *opClause,
-									 Var *varClause, Const *constantClause)
+									 Var *partitionColumn, Const *constantClause)
 {
 	PruningInstance *prune = context->currentPruningInstance;
 	List *btreeInterpretationList = NULL;
 	ListCell *btreeInterpretationCell = NULL;
 	bool matchedOp = false;
 
+	Assert(IsBinaryCoercible(constantClause->consttype, partitionColumn->vartype));
+
 	btreeInterpretationList =
 		get_op_btree_interpretation(opClause->opno);
 	foreach(btreeInterpretationCell, btreeInterpretationList)
@@ -838,6 +841,9 @@ AddHashRestrictionToInstance(ClauseWalkerContext *context, OpExpr *opClause,
 	List *btreeInterpretationList = NULL;
 	ListCell *btreeInterpretationCell = NULL;
 
+	/* be paranoid */
+	Assert(IsBinaryCoercible(constantClause->consttype, INT4OID));
+
 	btreeInterpretationList =
 		get_op_btree_interpretation(opClause->opno);
 	foreach(btreeInterpretationCell, btreeInterpretationList)

src/test/regress/expected/multi_prune_shard_list.out

@@ -203,3 +203,27 @@ SELECT print_sorted_shard_intervals('pruning_range');
  {800004,800005,800006,800007}
 (1 row)
 
+-- ===================================================================
+-- test pruning using values whose types are coerced
+-- ===================================================================
+CREATE TABLE coerce_hash (
+	id bigint NOT NULL,
+	value text NOT NULL
+);
+SELECT create_distributed_table('coerce_hash', 'id');
+ create_distributed_table 
+--------------------------
+ 
+(1 row)
+
+-- PostgreSQL will cast id to numeric rather than 1.0 to bigint...
+-- We used to blindly pass the RHS' Datum to our comparison func.,
+-- resulting in inaccurate pruning. An Assert now verifies type-
+-- compatibility; the following would crash the server in an Assert-
+-- before the underlying issue was addressed. It looks like a boring
+-- test now, but if the old behavior is restored, it should crash again.
+SELECT * FROM coerce_hash WHERE id = 1.0::numeric;
+ id | value 
+----+-------
+(0 rows)
+

src/test/regress/sql/multi_prune_shard_list.sql

@@ -119,3 +119,21 @@ SELECT print_sorted_shard_intervals('pruning_range');
 -- all shard placements are uninitialized
 UPDATE pg_dist_shard set shardminvalue = NULL, shardmaxvalue = NULL WHERE shardid = 103077;
 SELECT print_sorted_shard_intervals('pruning_range');
+
+-- ===================================================================
+-- test pruning using values whose types are coerced
+-- ===================================================================
+
+CREATE TABLE coerce_hash (
+	id bigint NOT NULL,
+	value text NOT NULL
+);
+SELECT create_distributed_table('coerce_hash', 'id');
+
+-- PostgreSQL will cast id to numeric rather than 1.0 to bigint...
+-- We used to blindly pass the RHS' Datum to our comparison func.,
+-- resulting in inaccurate pruning. An Assert now verifies type-
+-- compatibility; the following would crash the server in an Assert-
+-- before the underlying issue was addressed. It looks like a boring
+-- test now, but if the old behavior is restored, it should crash again.
+SELECT * FROM coerce_hash WHERE id = 1.0::numeric;