Hi!
Here's a slightly improved version of patch Tomas provided above (v2),
with cache invalidations and slices caching added, still as PoC.
The main issue I've encountered during tests is that when the same query
retrieves both slices and full value - slices, like substring(t,...) the order of
the values is not predictable, with text fields substrings are retrieved
before the full value and we cannot benefit from cache full value first
and use slices from cached value.
Yet the cache code is still very compact and affects only sources related
to detoasting.
Tomas, about HASH_ENTER - according to comments it could throw
an OOM error, so I've changed it to HASH_ENTER_NULL to avoid
new errors. In this case we would just have the value not cached
without an error.
-- Regards,
Nikita Malakhov
Postgres Professional
The Russian Postgres Company