On 8/11/16 8:45 AM, Tom Lane wrote:
> Jim Nasby <Jim.Nasby@BlueTreble.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.
Multiple -> or ->> operators, but all operating on the same field (which
I thought would mean a single datum that would end up detoasted?).
Some of these would have been nested ->/->>. In essence, this was a set
of nested views that ultimately pulled from a single JSONB field.
--
Jim Nasby, Data Architect, Blue Treble Consulting, Austin TX
Experts in Analytics, Data Architecture and PostgreSQL
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