Currently only IMMUTABLE constraints will exclude chunks from an UPDATE plan,
with this patch STABLE expressions will be used to exclude chunks as well.
This is a big performance improvement as chunks not matching partitioning
column constraints don't have to be scanned for UPDATEs.
Since the codepath for UPDATE is different for PG < 14 this patch only adds
the optimization for PG14.
With this patch the plan for UPDATE on hypertables looks like this:
Custom Scan (HypertableModify) (actual rows=0 loops=1)
-> Update on public.metrics_int2 (actual rows=0 loops=1)
Update on public.metrics_int2 metrics_int2_1
Update on _timescaledb_internal._hyper_1_1_chunk metrics_int2
Update on _timescaledb_internal._hyper_1_2_chunk metrics_int2
Update on _timescaledb_internal._hyper_1_3_chunk metrics_int2
-> Custom Scan (ChunkAppend) on public.metrics_int2 (actual rows=0 loops=1)
Output: '123'::text, metrics_int2.tableoid, metrics_int2.ctid
Startup Exclusion: true
Runtime Exclusion: false
Chunks excluded during startup: 3
-> Seq Scan on public.metrics_int2 metrics_int2_1 (actual rows=0 loops=1)
Output: metrics_int2_1.tableoid, metrics_int2_1.ctid
Filter: (metrics_int2_1."time" = length(version()))
