Limit max shards that can be created with split

src/backend/distributed/operations/shard_split.c

@@ -16,6 +16,7 @@
 #include "lib/stringinfo.h"
 #include "utils/builtins.h"
 #include "utils/lsyscache.h"
+#include "distributed/shared_library_init.h"
 #include "distributed/adaptive_executor.h"
 #include "distributed/colocation_utils.h"
 #include "distributed/metadata_cache.h"
@@ -223,7 +224,8 @@ ErrorIfCannotSplitShardExtended(SplitOperation splitOperation,
 
 	int splitPointsCount = list_length(shardSplitPointsList);
 	int nodeIdsCount = list_length(nodeIdsForPlacementList);
-	if (nodeIdsCount != splitPointsCount + 1)
+	int shardsCount = splitPointsCount + 1;
+	if (nodeIdsCount != shardsCount)
 	{
 		ereport(ERROR,
 				(errcode(ERRCODE_SYNTAX_ERROR),
@@ -234,6 +236,12 @@ ErrorIfCannotSplitShardExtended(SplitOperation splitOperation,
 					 splitPointsCount)));
 	}
 
+	if (shardsCount > MAX_SHARD_COUNT)
+	{
+		ereport(ERROR, (errmsg(
+							"Resulting shard count '%d' with split is greater than max shard count '%d' limit.",
+							shardsCount, MAX_SHARD_COUNT)));
+	}
 
 	Assert(shardIntervalToSplit->minValueExists);
 	Assert(shardIntervalToSplit->maxValueExists);

src/test/regress/expected/citus_split_shard_by_split_points_negative.out

@@ -83,6 +83,15 @@ SELECT citus_split_shard_by_split_points(
 	ARRAY['-1073741825'], -- Split point equals shard's max value.
 	ARRAY[:worker_1_node, :worker_2_node]);
 ERROR:  Invalid split point -1073741825, as split points should be inclusive. Please use -1073741826 instead.
+-- UDF fails if resulting shard count from split greater than MAX_SHARD_COUNT (64000)
+-- 64000 split point definee 64000+1 way split (64001 worker nodes needed).
+WITH shard_ranges AS (SELECT ((-2147483648 + indx))::text as split_points, :worker_1_node as node_ids FROM generate_series(1,64000) indx )
+SELECT citus_split_shard_by_split_points(
+    49761300,
+    array_agg(split_points),
+    array_agg(node_ids) || :worker_1_node) --placement node list should exceed split points by one.
+FROM shard_ranges;
+ERROR:  Resulting shard count '64001' with split is greater than max shard count '64000' limit.
 -- UDF fails where source shard cannot be split further i.e min and max range is equal.
 -- Create a Shard where range cannot be split further
 SELECT isolate_tenant_to_new_shard('table_to_split', 1);

src/test/regress/sql/citus_split_shard_by_split_points_negative.sql

@@ -74,6 +74,15 @@ SELECT citus_split_shard_by_split_points(
 	ARRAY['-1073741825'], -- Split point equals shard's max value.
 	ARRAY[:worker_1_node, :worker_2_node]);
 
+-- UDF fails if resulting shard count from split greater than MAX_SHARD_COUNT (64000)
+-- 64000 split point definee 64000+1 way split (64001 worker nodes needed).
+WITH shard_ranges AS (SELECT ((-2147483648 + indx))::text as split_points, :worker_1_node as node_ids FROM generate_series(1,64000) indx )
+SELECT citus_split_shard_by_split_points(
+    49761300,
+    array_agg(split_points),
+    array_agg(node_ids) || :worker_1_node) --placement node list should exceed split points by one.
+FROM shard_ranges;
+
 -- UDF fails where source shard cannot be split further i.e min and max range is equal.
 -- Create a Shard where range cannot be split further
 SELECT isolate_tenant_to_new_shard('table_to_split', 1);