Add DistTableCacheEntry->hasOverlappingShardInterval.

This determines whether it's possible to perform binary search on
sortedShardIntervalArray or not.  If e.g. two shards have overlapping
ranges, that'd be prohibitive.

That'll be useful in later commit introducing faster shard pruning.

src/backend/distributed/utils/metadata_cache.c

@@ -131,6 +131,9 @@ static bool HasUniformHashDistribution(ShardInterval **shardIntervalArray,
 									   int shardIntervalArrayLength);
 static bool HasUninitializedShardInterval(ShardInterval **sortedShardIntervalArray,
 										  int shardCount);
+static bool HasOverlappingShardInterval(ShardInterval **shardIntervalArray,
+										int shardIntervalArrayLength,
+										FmgrInfo *shardIntervalSortCompareFunction);
 static void InitializeDistTableCache(void);
 static void InitializeWorkerNodeCache(void);
 static uint32 WorkerNodeHashCode(const void *key, Size keySize);
@@ -700,6 +703,7 @@ BuildCachedShardList(DistTableCacheEntry *cacheEntry)
 	if (cacheEntry->partitionMethod == DISTRIBUTE_BY_NONE)
 	{
 		cacheEntry->hasUninitializedShardInterval = true;
+		cacheEntry->hasOverlappingShardInterval = true;
 
 		/*
 		 * Note that during create_reference_table() call,
@@ -728,6 +732,35 @@ BuildCachedShardList(DistTableCacheEntry *cacheEntry)
 		cacheEntry->hasUninitializedShardInterval =
 			HasUninitializedShardInterval(sortedShardIntervalArray,
 										  shardIntervalArrayLength);
+
+		if (!cacheEntry->hasUninitializedShardInterval)
+		{
+			cacheEntry->hasOverlappingShardInterval =
+				HasOverlappingShardInterval(sortedShardIntervalArray,
+											shardIntervalArrayLength,
+											shardIntervalCompareFunction);
+		}
+		else
+		{
+			cacheEntry->hasOverlappingShardInterval = true;
+		}
+
+		/*
+		 * If table is hash-partitioned and has shards, there never should be
+		 * any uninitalized shards.  Historically we've not prevented that for
+		 * range partitioned tables, but it might be a good idea to start
+		 * doing so.
+		 */
+		if (cacheEntry->partitionMethod == DISTRIBUTE_BY_HASH &&
+			cacheEntry->hasUninitializedShardInterval)
+		{
+			ereport(ERROR, (errmsg("hash partitioned table has uninitialized shards")));
+		}
+		if (cacheEntry->partitionMethod == DISTRIBUTE_BY_HASH &&
+			cacheEntry->hasOverlappingShardInterval)
+		{
+			ereport(ERROR, (errmsg("hash partitioned table has overlapping shards")));
+		}
 	}
 
 
@@ -903,6 +936,52 @@ HasUninitializedShardInterval(ShardInterval **sortedShardIntervalArray, int shar
 }
 
 
+/*
+ * HasOverlappingShardInterval determines whether the given list of sorted
+ * shards has overlapping ranges.
+ */
+static bool
+HasOverlappingShardInterval(ShardInterval **shardIntervalArray,
+							int shardIntervalArrayLength,
+							FmgrInfo *shardIntervalSortCompareFunction)
+{
+	int shardIndex = 0;
+	ShardInterval *lastShardInterval = NULL;
+	Datum comparisonDatum = 0;
+	int comparisonResult = 0;
+
+	/* zero/a single shard can't overlap */
+	if (shardIntervalArrayLength < 2)
+	{
+		return false;
+	}
+
+	lastShardInterval = shardIntervalArray[0];
+	for (shardIndex = 1; shardIndex < shardIntervalArrayLength; shardIndex++)
+	{
+		ShardInterval *curShardInterval = shardIntervalArray[shardIndex];
+
+		/* only called if !hasUninitializedShardInterval */
+		Assert(lastShardInterval->minValueExists && lastShardInterval->maxValueExists);
+		Assert(curShardInterval->minValueExists && curShardInterval->maxValueExists);
+
+		comparisonDatum = CompareCall2(shardIntervalSortCompareFunction,
+									   lastShardInterval->maxValue,
+									   curShardInterval->minValue);
+		comparisonResult = DatumGetInt32(comparisonDatum);
+
+		if (comparisonResult >= 0)
+		{
+			return true;
+		}
+
+		lastShardInterval = curShardInterval;
+	}
+
+	return false;
+}
+
+
 /*
  * CitusHasBeenLoaded returns true if the citus extension has been created
  * in the current database and the extension script has been executed. Otherwise,
@@ -1832,6 +1911,7 @@ ResetDistTableCacheEntry(DistTableCacheEntry *cacheEntry)
 	cacheEntry->shardIntervalArrayLength = 0;
 	cacheEntry->hasUninitializedShardInterval = false;
 	cacheEntry->hasUniformHashDistribution = false;
+	cacheEntry->hasOverlappingShardInterval = false;
 }
 
 

src/include/distributed/metadata_cache.h

@@ -36,6 +36,7 @@ typedef struct
 	bool isDistributedTable;
 	bool hasUninitializedShardInterval;
 	bool hasUniformHashDistribution; /* valid for hash partitioned tables */
+	bool hasOverlappingShardInterval;
 
 	/* pg_dist_partition metadata for this table */
 	char *partitionKeyString;

src/test/regress/input/multi_outer_join_reference.source

@@ -167,7 +167,7 @@ FROM
 -- load some more data
 \copy multi_outer_join_right_reference FROM '@abs_srcdir@/data/customer-21-30.data' with delimiter '|'
 
--- Update shards so that they do not have 1-1 matching. We should error here.
+-- Update shards so that they do not have 1-1 matching, triggering an error.
 UPDATE pg_dist_shard SET shardminvalue = '2147483646' WHERE shardid = 1260006;
 UPDATE pg_dist_shard SET shardmaxvalue = '2147483647' WHERE shardid = 1260006;
 SELECT

src/test/regress/output/multi_outer_join_reference.source

@@ -229,15 +229,14 @@ LOG:  join order: [ "multi_outer_join_left_hash" ][ broadcast join "multi_outer_
 
 -- load some more data
 \copy multi_outer_join_right_reference FROM '@abs_srcdir@/data/customer-21-30.data' with delimiter '|'
--- Update shards so that they do not have 1-1 matching. We should error here.
+-- Update shards so that they do not have 1-1 matching, triggering an error.
 UPDATE pg_dist_shard SET shardminvalue = '2147483646' WHERE shardid = 1260006;
 UPDATE pg_dist_shard SET shardmaxvalue = '2147483647' WHERE shardid = 1260006;
 SELECT
 	min(l_custkey), max(l_custkey)
 FROM
 	multi_outer_join_left_hash a LEFT JOIN multi_outer_join_right_hash b ON (l_custkey = r_custkey);
-ERROR:  cannot perform distributed planning on this query
-DETAIL:  Shards of relations in outer join queries must have 1-to-1 shard partitioning
+ERROR:  hash partitioned table has overlapping shards
 UPDATE pg_dist_shard SET shardminvalue = '-2147483648' WHERE shardid = 1260006;
 UPDATE pg_dist_shard SET shardmaxvalue = '-1073741825' WHERE shardid = 1260006;
 -- empty tables