Introduce drop_timeseries_table UDF to drop metadata

src/backend/distributed/sql/citus--10.1-1--10.2-1.sql

@@ -16,7 +16,9 @@ ALTER TABLE pg_catalog.pg_dist_placement ADD CONSTRAINT placement_shardid_groupi
 #include "udfs/citus_internal_update_placement_metadata/10.2-1.sql";
 #include "udfs/citus_internal_delete_shard_metadata/10.2-1.sql";
 #include "udfs/citus_internal_update_relation_colocation/10.2-1.sql";
+#include "udfs/citus_drop_trigger/10.2-1.sql"
 #include "../../timeseries/sql/timeseries--10.1-1--10.2-1.sql"
 #include "../../timeseries/sql/udfs/create_timeseries_table/10.2-1.sql"
+#include "../../timeseries/sql/udfs/drop_timeseries_table/10.2-1.sql"
 #include "../../timeseries/sql/udfs/create_missing_partitions/10.2-1.sql"
 #include "../../timeseries/sql/udfs/get_missing_partition_ranges/10.2-1.sql"

src/backend/distributed/sql/udfs/citus_drop_trigger/10.2-1.sql

@@ -0,0 +1,50 @@
+CREATE OR REPLACE FUNCTION pg_catalog.notify_constraint_dropped()
+    RETURNS void
+    LANGUAGE C STRICT
+    AS 'MODULE_PATHNAME', $$notify_constraint_dropped$$;
+
+CREATE OR REPLACE FUNCTION pg_catalog.citus_drop_trigger()
+    RETURNS event_trigger
+    LANGUAGE plpgsql
+    SET search_path = pg_catalog
+    AS $cdbdt$
+DECLARE
+    constraint_event_count INTEGER;
+    v_obj record;
+    sequence_names text[] := '{}';
+    table_colocation_id integer;
+    propagate_drop boolean := false;
+BEGIN
+    FOR v_obj IN SELECT * FROM pg_event_trigger_dropped_objects()
+                 WHERE object_type IN ('table', 'foreign table')
+    LOOP
+        -- first drop the table and metadata on the workers
+        -- then drop all the shards on the workers
+        -- finally remove the pg_dist_partition entry on the coordinator
+        PERFORM master_remove_distributed_table_metadata_from_workers(v_obj.objid, v_obj.schema_name, v_obj.object_name);
+        PERFORM citus_drop_all_shards(v_obj.objid, v_obj.schema_name, v_obj.object_name);
+        PERFORM master_remove_partition_metadata(v_obj.objid, v_obj.schema_name, v_obj.object_name);
+        PERFORM drop_timeseries_table(v_obj.objid);
+    END LOOP;
+
+    -- remove entries from citus.pg_dist_object for all dropped root (objsubid = 0) objects
+    FOR v_obj IN SELECT * FROM pg_event_trigger_dropped_objects()
+    LOOP
+        PERFORM master_unmark_object_distributed(v_obj.classid, v_obj.objid, v_obj.objsubid);
+    END LOOP;
+
+    SELECT COUNT(*) INTO constraint_event_count
+    FROM pg_event_trigger_dropped_objects()
+    WHERE object_type IN ('table constraint');
+
+    IF constraint_event_count > 0
+    THEN
+        -- Tell utility hook that a table constraint is dropped so we might
+        -- need to undistribute some of the citus local tables that are not
+        -- connected to any reference tables.
+        PERFORM notify_constraint_dropped();
+    END IF;
+END;
+$cdbdt$;
+COMMENT ON FUNCTION pg_catalog.citus_drop_trigger()
+    IS 'perform checks and actions at the end of DROP actions';

src/backend/distributed/sql/udfs/citus_drop_trigger/latest.sql

@@ -24,6 +24,7 @@ BEGIN
         PERFORM master_remove_distributed_table_metadata_from_workers(v_obj.objid, v_obj.schema_name, v_obj.object_name);
         PERFORM citus_drop_all_shards(v_obj.objid, v_obj.schema_name, v_obj.object_name);
         PERFORM master_remove_partition_metadata(v_obj.objid, v_obj.schema_name, v_obj.object_name);
+        PERFORM drop_timeseries_table(v_obj.objid);
     END LOOP;
 
     -- remove entries from citus.pg_dist_object for all dropped root (objsubid = 0) objects

src/backend/timeseries/create_timeseries_table.c

@@ -32,8 +32,6 @@
 #include "distributed/resource_lock.h"
 #include "timeseries/timeseries_utils.h"
 
-#define Natts_citus_timeseries_tables 6
-
 PG_FUNCTION_INFO_V1(create_timeseries_table);
 
 static void InitiateTimeseriesTablePartitions(Oid relationId);

src/backend/timeseries/drop_timeseries_table.c

@@ -0,0 +1,68 @@
+/*-------------------------------------------------------------------------
+ *
+ * drop_timeseries_table.c
+ *	  Routines related to the drop of timeseries tables.
+ *
+ * Copyright (c) Citus Data, Inc.
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+#include "miscadmin.h"
+
+#include "access/genam.h"
+#include "access/skey.h"
+#include "access/xact.h"
+#include "catalog/indexing.h"
+#include "storage/lockdefs.h"
+#include "utils/elog.h"
+#include "utils/relcache.h"
+#include "utils/fmgroids.h"
+
+#include "distributed/metadata_cache.h"
+#include "timeseries/timeseries_utils.h"
+
+PG_FUNCTION_INFO_V1(drop_timeseries_table);
+
+/*
+ * drop_timeseries_table gets the table oid, then it drops
+ * all the metadata related to it. Note that this function doesn't
+ * drop any partitions or any data of the given table.
+ * 
+ * TODO: Add unscheduling for automated jobs as well.
+ */
+Datum
+drop_timeseries_table(PG_FUNCTION_ARGS)
+{
+	CheckCitusVersion(ERROR);
+
+	if (PG_ARGISNULL(0))
+	{
+		PG_RETURN_VOID();
+	}
+
+	Oid relationId = PG_GETARG_OID(0);
+
+    ScanKeyData relIdKey[1];
+	Relation timeseriesRelation = table_open(CitusTimeseriesTablesRelationId(), AccessShareLock);
+
+	ScanKeyInit(&relIdKey[0],
+				Anum_citus_timeseries_table_relation_id,
+				BTEqualStrategyNumber, F_OIDEQ,
+				ObjectIdGetDatum(relationId));
+
+	SysScanDesc timeseriesRelScan = systable_beginscan(timeseriesRelation, InvalidOid, false, NULL, 1, relIdKey);
+	HeapTuple timeseriesTuple = systable_getnext(timeseriesRelScan);
+
+	if (HeapTupleIsValid(timeseriesTuple))
+	{
+		CatalogTupleDelete(timeseriesRelation, &timeseriesTuple->t_self);
+		CommandCounterIncrement();
+	}
+    
+    systable_endscan(timeseriesRelScan);
+	table_close(timeseriesRelation, NoLock);
+
+	PG_RETURN_VOID();
+}

src/backend/timeseries/sql/udfs/drop_timeseries_table/10.2-1.sql

@@ -0,0 +1,10 @@
+CREATE OR REPLACE FUNCTION pg_catalog.drop_timeseries_table(
+    logicalrelid regclass)
+    RETURNS void
+    LANGUAGE C
+AS 'MODULE_PATHNAME', 'drop_timeseries_table';
+
+COMMENT ON FUNCTION pg_catalog.drop_timeseries_table(
+    logicalrelid regclass)
+IS 'drops a citus timeseries table by removing metadata';
+-- TODO: Update comment for unscheduling

src/backend/timeseries/sql/udfs/drop_timeseries_table/latest.sql

@@ -0,0 +1,10 @@
+CREATE OR REPLACE FUNCTION pg_catalog.drop_timeseries_table(
+    logicalrelid regclass)
+    RETURNS void
+    LANGUAGE C
+AS 'MODULE_PATHNAME', 'drop_timeseries_table';
+
+COMMENT ON FUNCTION pg_catalog.drop_timeseries_table(
+    logicalrelid regclass)
+IS 'drops a citus timeseries table by removing metadata';
+-- TODO: Update comment for unscheduling

src/backend/timeseries/timeseries_utils.c

@@ -22,11 +22,6 @@
 
 #include "timeseries/timeseries_utils.h"
 
-#define INTERVAL_TO_SEC(ivp) \
-	(((double) (ivp)->time) / ((double) USECS_PER_SEC) + \
-	 (ivp)->day * (24.0 * SECS_PER_HOUR) + \
-	 (ivp)->month * (30.0 * SECS_PER_DAY))
-
 /*
  * Get the relation id for citus_timeseries_tables metadata table
  */
@@ -37,8 +32,8 @@ CitusTimeseriesTablesRelationId()
 									   TimeseriesNamespaceId());
 	if (relationId == InvalidOid)
 	{
-		ereport(ERROR, (errmsg(
-							"cache lookup failed for citus_timeseries_tables, called too early?")));
+		ereport(ERROR, (errmsg("cache lookup failed for citus_timeseries_tables,"
+							   "called too early?")));
 	}
 
 	return relationId;

src/include/timeseries/timeseries_utils.h

@@ -16,6 +16,19 @@
 #include "server/datatype/timestamp.h"
 #include "server/partitioning/partdefs.h"
 
+#define Natts_citus_timeseries_tables 6
+#define Anum_citus_timeseries_table_relation_id 1
+#define Anum_citus_timeseries_table_partition_interval 2
+#define Anum_citus_timeseries_table_premake_interval_count 3
+#define Anum_citus_timeseries_table_postmake_interval_count 4
+#define Anum_citus_timeseries_table_compression_threshold 5
+#define Anum_citus_timeseries_table_retention_threshold 6
+
+#define INTERVAL_TO_SEC(ivp) \
+	(((double) (ivp)->time) / ((double) USECS_PER_SEC) + \
+	 (ivp)->day * (24.0 * SECS_PER_HOUR) + \
+	 (ivp)->month * (30.0 * SECS_PER_DAY))
+
 extern Oid CitusTimeseriesTablesRelationId(void);
 extern Oid TimeseriesNamespaceId(void);
 extern bool CheckIntervalAlignmentWithThresholds(Interval *partitionInterval,