Re: Force re-compression with lz4

Florents Tselai wrote:

> I have a table storing mostly text data (40M+ rows) that has
> pg_total_relation_size ~670GB.
> I’ve just upgraded to postgres 14 and I’m now eager to try the new LZ4
> compression.

You could start experimenting with data samples rather than the
full contents.

FWIW, in my case I've found that the compression ratio of lz4 was only
marginally better than pglz (like 2% on text).
As for decompression time, it doesn't seem to differ significantly
from pglz, so overall, recompressing existing data did not seem
worth the trouble.

However lz4 appears to be much faster to compress than pglz, so its
benefit is clear in terms of CPU usage for future insertions.

Best regards,
--
Daniel Vérité
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