Re: Jsonb extraction very slow

On Thu, Aug 11, 2016 at 8:45 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Jim Nasby <Jim(dot)Nasby(at)BlueTreble(dot)com> writes:
>> I never dug into why. As Tom posited, decompression might explain the
>> time to get a single key out. Getting 10 keys instead of just 1 wasn't
>> 10x more expensive, but it was significantly more expensive than just
>> getting a single key.
>
> What were you doing to "get ten keys out"? If those were ten separate
> JSON operators, they'd likely have done ten separate decompressions.
> You'd have saved something by having the TOAST data already fetched into
> shared buffers, but it'd still hardly be free.

Huh -- FWICT there is no way to pull N values from a jsonb with # of
items M for any value of N other than 1 or M with a single operation.

merlin