PG17 compatibility: fix pg16 to pg17 upgrade

In citus_prepapre_upgrade(), don't drop any_value when upgrading from
PG16+, because PG16+ has its own any_value function. Attempting to do
so results in an error. When 16 becomes the minimum supported Postgres
version, the drop statements can be removed.

src/backend/distributed/sql/citus--12.1-1--13.0-1.sql

@@ -1,3 +1,4 @@
 -- citus--12.1-1--13.0-1.sql
 
 -- bump version to 13.0-1
+#include "udfs/citus_prepare_pg_upgrade/13.0-1.sql"

src/backend/distributed/sql/udfs/citus_prepare_pg_upgrade/13.0-1.sql

@@ -0,0 +1,100 @@
+CREATE OR REPLACE FUNCTION pg_catalog.citus_prepare_pg_upgrade()
+    RETURNS void
+    LANGUAGE plpgsql
+    SET search_path = pg_catalog
+    AS $cppu$
+BEGIN
+
+    DELETE FROM pg_depend WHERE
+        objid IN (SELECT oid FROM pg_proc WHERE proname = 'array_cat_agg') AND
+        refobjid IN (select oid from pg_extension where extname = 'citus');
+    --
+    -- We are dropping the aggregates because postgres 14 changed
+    -- array_cat type from anyarray to anycompatiblearray. When
+    -- upgrading to pg14, specifically when running pg_restore on
+    -- array_cat_agg we would get an error. So we drop the aggregate
+    -- and create the right one on citus_finish_pg_upgrade.
+
+    DROP AGGREGATE IF EXISTS array_cat_agg(anyarray);
+    DROP AGGREGATE IF EXISTS array_cat_agg(anycompatiblearray);
+
+    -- We should drop any_value because PG16+ has its own any_value function
+    -- We can remove this part when we drop support for PG16
+    IF substring(current_Setting('server_version'), '\d+')::int < 16 THEN
+        DELETE FROM pg_depend WHERE
+            objid IN (SELECT oid FROM pg_proc WHERE proname = 'any_value' OR proname = 'any_value_agg') AND
+            refobjid IN (select oid from pg_extension where extname = 'citus');
+        DROP AGGREGATE IF EXISTS pg_catalog.any_value(anyelement);
+        DROP FUNCTION IF EXISTS pg_catalog.any_value_agg(anyelement, anyelement);
+    END IF;
+
+    --
+    -- Drop existing backup tables
+    --
+    DROP TABLE IF EXISTS public.pg_dist_partition;
+    DROP TABLE IF EXISTS public.pg_dist_shard;
+    DROP TABLE IF EXISTS public.pg_dist_placement;
+    DROP TABLE IF EXISTS public.pg_dist_node_metadata;
+    DROP TABLE IF EXISTS public.pg_dist_node;
+    DROP TABLE IF EXISTS public.pg_dist_local_group;
+    DROP TABLE IF EXISTS public.pg_dist_transaction;
+    DROP TABLE IF EXISTS public.pg_dist_colocation;
+    DROP TABLE IF EXISTS public.pg_dist_authinfo;
+    DROP TABLE IF EXISTS public.pg_dist_poolinfo;
+    DROP TABLE IF EXISTS public.pg_dist_rebalance_strategy;
+    DROP TABLE IF EXISTS public.pg_dist_object;
+    DROP TABLE IF EXISTS public.pg_dist_cleanup;
+    DROP TABLE IF EXISTS public.pg_dist_schema;
+    DROP TABLE IF EXISTS public.pg_dist_clock_logical_seq;
+
+    --
+    -- backup citus catalog tables
+    --
+    CREATE TABLE public.pg_dist_partition AS SELECT * FROM pg_catalog.pg_dist_partition;
+    CREATE TABLE public.pg_dist_shard AS SELECT * FROM pg_catalog.pg_dist_shard;
+    CREATE TABLE public.pg_dist_placement AS SELECT * FROM pg_catalog.pg_dist_placement;
+    CREATE TABLE public.pg_dist_node_metadata AS SELECT * FROM pg_catalog.pg_dist_node_metadata;
+    CREATE TABLE public.pg_dist_node AS SELECT * FROM pg_catalog.pg_dist_node;
+    CREATE TABLE public.pg_dist_local_group AS SELECT * FROM pg_catalog.pg_dist_local_group;
+    CREATE TABLE public.pg_dist_transaction AS SELECT * FROM pg_catalog.pg_dist_transaction;
+    CREATE TABLE public.pg_dist_colocation AS SELECT * FROM pg_catalog.pg_dist_colocation;
+    CREATE TABLE public.pg_dist_cleanup AS SELECT * FROM pg_catalog.pg_dist_cleanup;
+    -- save names of the tenant schemas instead of their oids because the oids might change after pg upgrade
+    CREATE TABLE public.pg_dist_schema AS SELECT schemaid::regnamespace::text AS schemaname, colocationid FROM pg_catalog.pg_dist_schema;
+    -- enterprise catalog tables
+    CREATE TABLE public.pg_dist_authinfo AS SELECT * FROM pg_catalog.pg_dist_authinfo;
+    CREATE TABLE public.pg_dist_poolinfo AS SELECT * FROM pg_catalog.pg_dist_poolinfo;
+    -- sequences
+    CREATE TABLE public.pg_dist_clock_logical_seq AS SELECT last_value FROM pg_catalog.pg_dist_clock_logical_seq;
+    CREATE TABLE public.pg_dist_rebalance_strategy AS SELECT
+        name,
+        default_strategy,
+        shard_cost_function::regprocedure::text,
+        node_capacity_function::regprocedure::text,
+        shard_allowed_on_node_function::regprocedure::text,
+        default_threshold,
+        minimum_threshold,
+        improvement_threshold
+    FROM pg_catalog.pg_dist_rebalance_strategy;
+
+    -- store upgrade stable identifiers on pg_dist_object catalog
+    CREATE TABLE public.pg_dist_object AS SELECT
+       address.type,
+       address.object_names,
+       address.object_args,
+       objects.distribution_argument_index,
+       objects.colocationid
+    FROM pg_catalog.pg_dist_object objects,
+         pg_catalog.pg_identify_object_as_address(objects.classid, objects.objid, objects.objsubid) address;
+
+    -- if we are upgrading from PG14/PG15 to PG16+,
+    -- we will need to regenerate the partkeys because they will include varnullingrels as well.
+    -- so we save the partkeys as column names here
+    CREATE TABLE IF NOT EXISTS public.pg_dist_partkeys_pre_16_upgrade AS
+    SELECT logicalrelid, column_to_column_name(logicalrelid, partkey) as col_name
+    FROM pg_catalog.pg_dist_partition WHERE partkey IS NOT NULL AND partkey NOT ILIKE '%varnullingrels%';
+END;
+$cppu$;
+
+COMMENT ON FUNCTION pg_catalog.citus_prepare_pg_upgrade()
+    IS 'perform tasks to copy citus settings to a location that could later be restored after pg_upgrade is done';

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

@@ -18,13 +18,15 @@ BEGIN
     DROP AGGREGATE IF EXISTS array_cat_agg(anyarray);
     DROP AGGREGATE IF EXISTS array_cat_agg(anycompatiblearray);
 
-    -- We should drop any_value because PG16 has its own any_value function
+    -- We should drop any_value because PG16+ has its own any_value function
     -- We can remove this part when we drop support for PG16
-    DELETE FROM pg_depend WHERE
-        objid IN (SELECT oid FROM pg_proc WHERE proname = 'any_value' OR proname = 'any_value_agg') AND
-        refobjid IN (select oid from pg_extension where extname = 'citus');
-    DROP AGGREGATE IF EXISTS pg_catalog.any_value(anyelement);
-    DROP FUNCTION IF EXISTS pg_catalog.any_value_agg(anyelement, anyelement);
+    IF substring(current_Setting('server_version'), '\d+')::int < 16 THEN
+        DELETE FROM pg_depend WHERE
+            objid IN (SELECT oid FROM pg_proc WHERE proname = 'any_value' OR proname = 'any_value_agg') AND
+            refobjid IN (select oid from pg_extension where extname = 'citus');
+        DROP AGGREGATE IF EXISTS pg_catalog.any_value(anyelement);
+        DROP FUNCTION IF EXISTS pg_catalog.any_value_agg(anyelement, anyelement);
+    END IF;
 
     --
     -- Drop existing backup tables