This patch adds an optimization to the DecompressChunk node. If the
query 'order by' and the compression 'order by' are compatible (query
'order by' is equal or a prefix of compression 'order by'), the
compressed batches of the segments are decompressed in parallel and
merged using a binary heep. This preserves the ordering and the sorting
of the result can be prevented. Especially LIMIT queries benefit from
this optimization because only the first tuples of some batches have to
be decompressed. Previously, all segments were completely decompressed
and sorted.
Fixes: #4223
Co-authored-by: Sotiris Stamokostas <sotiris@timescale.com>
With memoize enabled PG14 append tests produce a very different
plan compared to previous PG versions. To make comparing plans
between PG versions easier we disable memoize for PG14.
PG14 also modified how EXTRACT is shown in EXPLAIN output
so any query using EXTRACT will have different EXPLAIN output
between PG14 and previous versions.
The sql tests still had version checks and would run EXPLAIN
with different parameters depending on postgres version. Since
all supported postgres versions now support all the parameters
we use we can safely remove the version check.
