From 2bd8f8f12e869416c088df11c4c9b385a2ebe0e1 Mon Sep 17 00:00:00 2001
From: Metin Doslu <metin@citusdata.com>
Date: Thu, 19 Jan 2017 18:18:57 +0200
Subject: [PATCH] Add a function to delete shard metadata from MX nodes

---
 .../distributed/metadata/metadata_sync.c      | 33 ++++++++++++++++++-
 src/include/distributed/metadata_sync.h       |  1 +
 2 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/src/backend/distributed/metadata/metadata_sync.c b/src/backend/distributed/metadata/metadata_sync.c
index d0bbf5e05..b69ec3139 100644
--- a/src/backend/distributed/metadata/metadata_sync.c
+++ b/src/backend/distributed/metadata/metadata_sync.c
@@ -513,7 +513,7 @@ TableOwnerResetCommand(Oid relationId)
 
 
 /*
- * ShardListInsertCommand generates a singe command that can be
+ * ShardListInsertCommand generates a single command that can be
  * executed to replicate shard and shard placement metadata for the
  * given shard intervals. The function assumes that each shard has a
  * single placement, and asserts this information.
@@ -634,6 +634,37 @@ ShardListInsertCommand(List *shardIntervalList)
 }
 
 
+/*
+ * ShardListDeleteCommand generates a command list that can be executed to delete
+ * shard and shard placement metadata for the given shard.
+ */
+List *
+ShardDeleteCommandList(ShardInterval *shardInterval)
+{
+	uint64 shardId = shardInterval->shardId;
+	List *commandList = NIL;
+	StringInfo deletePlacementCommand = NULL;
+	StringInfo deleteShardCommand = NULL;
+
+	/* create command to delete shard placements */
+	deletePlacementCommand = makeStringInfo();
+	appendStringInfo(deletePlacementCommand,
+					 "DELETE FROM pg_dist_shard_placement WHERE shardid = %lu",
+					 shardId);
+
+	commandList = lappend(commandList, deletePlacementCommand->data);
+
+	/* create command to delete shard */
+	deleteShardCommand = makeStringInfo();
+	appendStringInfo(deleteShardCommand,
+					 "DELETE FROM pg_dist_shard WHERE shardid = %lu", shardId);
+
+	commandList = lappend(commandList, deleteShardCommand->data);
+
+	return commandList;
+}
+
+
 /*
  * NodeDeleteCommand generate a command that can be
  * executed to delete the metadata for a worker node.
diff --git a/src/include/distributed/metadata_sync.h b/src/include/distributed/metadata_sync.h
index c9fef4e1c..f14a9dcd3 100644
--- a/src/include/distributed/metadata_sync.h
+++ b/src/include/distributed/metadata_sync.h
@@ -28,6 +28,7 @@ extern char * DistributionDeleteCommand(char *schemaName,
 extern char * TableOwnerResetCommand(Oid distributedRelationId);
 extern char * NodeListInsertCommand(List *workerNodeList);
 extern List * ShardListInsertCommand(List *shardIntervalList);
+extern List * ShardDeleteCommandList(ShardInterval *shardInterval);
 extern char * NodeDeleteCommand(uint32 nodeId);
 extern char * ColocationIdUpdateCommand(Oid relationId, uint32 colocationId);
 extern char * CreateSchemaDDLCommand(Oid schemaId);