On Sun, Aug 18, 2019 at 12:35 PM Justin Pryzby <pry...@telsasoft.com> wrote:
> > . I was missing a way to check for compression ratio; Here are the ways to check compression ratio for zedstore: Table level: select sum(uncompressedsz::numeric) / sum(totalsz) as compratio from pg_zs_btree_pages(<tablename>); Per column level: select attno, count(*), sum(uncompressedsz::numeric) / sum(totalsz) as compratio from pg_zs_btree_pages(<tablename>) group by attno order by attno; > it looks like zedstore > with lz4 gets ~4.6x for our largest customer's largest table. zfs using > compress=gzip-1 gives 6x compression across all their partitioned > tables, > and I'm surprised it beats zedstore . > What kind of tables did you use? Is it possible to give us the schema of the table? Did you perform 'INSERT INTO ... SELECT' or COPY? Currently COPY give better compression ratios than single INSERT because it generates less pages for meta data. Using the above per column level compression ratio will provide which columns have lower compression ratio. We plan to add other compression algorithms like RLE and delta encoding which should give better compression ratios for column store along with LZ4.
