New feature tier policy

sql/timeseries.sql

@@ -7,7 +7,11 @@ CREATE TABLE @extschema@.ts_config(
   partition_duration interval NOT NULL,
   partition_lead_time interval NOT NULL,
   retention_duration interval,
-  compression_duration interval);
+  tier_duration interval,
+  compression_duration interval,
+  CONSTRAINT policy_duration_order_check 
+  CHECK(compression_duration < tier_duration 
+	AND tier_duration < retention_duration));
 
 -- Enhances an existing table with our time-series best practices. Basically
 -- the entry point to this extension. Minimally, a user must create a table
@@ -613,3 +617,54 @@ CREATE AGGREGATE locf(anyelement) (
   SFUNC = locf_agg,
   STYPE = anyelement
 );
+
+-- This function sets a tier to object store policy on an existing time-series table, which
+-- ensures that all partitions older than a particular offset (from present) are
+-- automatically moved to a S3 storage.
+--
+-- Returns the previous tier duration, or NULL if none was set.
+CREATE OR REPLACE FUNCTION @extschema@.set_ts_tier_policy(target_table_id regclass, new_tier interval)
+ RETURNS interval
+ LANGUAGE plpgsql
+AS $function$
+DECLARE
+  table_name text;
+  prev_tier interval;
+BEGIN
+  SELECT tier_duration
+    INTO prev_tier
+    FROM @extschema@.ts_config
+    WHERE "table_id"=target_table_id
+    FOR UPDATE;
+  IF NOT FOUND THEN
+    RAISE object_not_in_prerequisite_state USING
+      MESSAGE = 'could not fetch tier policy',
+      DETAIL  = 'Target table was not time-series enhanced',
+      HINT    = format('Call %L to enable time-series enhancements', 'enable_ts_table');
+  END IF;
+
+  UPDATE @extschema@.ts_config
+    SET "tier_duration"=new_tier
+    WHERE "table_id"=target_table_id;
+
+  RETURN prev_tier;
+END;
+$function$;
+
+
+-- Unsets any tier policy on the specified table. Returns the old policy,
+-- if one was set.
+CREATE OR REPLACE
+FUNCTION @extschema@.clear_ts_tier_policy(target_table_id regclass)
+  RETURNS interval
+  LANGUAGE plpgsql
+AS $function$
+DECLARE
+  prev_tier interval;
+BEGIN
+  SELECT set_ts_tier_policy(target_table_id, NULL) INTO prev_tier;
+
+  RETURN prev_tier;
+END;
+$function$;
+

timeseries.control

@@ -2,4 +2,4 @@
 comment = 'Convenience API for Tembo time series stack'
 default_version = '0.1.5'
 module_pathname = '$libdir/timeseries'
-requires = 'columnar, pg_cron, pg_partman'
+requires = 'columnar, pg_cron, pg_partman, pg_tier'