| Lists: | pgsql-hackers |
|---|
| From: | Alexander Korotkov <aekorotkov(at)gmail(dot)com> |
|---|---|
| To: | pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Proposal: collect frequency statistics for arrays |
| Date: | 2011-02-18 18:51:08 |
| Message-ID: | AANLkTikiruxOYh6jE_ETK7u4sEW6VXXqFK3Xn0-zVxoe@mail.gmail.com |
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| Lists: | pgsql-hackers |
Hackers,
I have following proposal. Currently the ts_typanalyze function accumulates
frequency statistics for ts_vector using lossy counting technique. But no
frequency statistics is collecting over arrays. I'm going to generalize
ts_typanalyze to make it collecting statistics for arrays too. ts_typanalyze
internally uses lexeme comparison and hashing. I'm going to use functions
from default btree and hash opclasses of array element type in this
capacity. Collected frequency statistics for arrays can be used for && and
@> operators selectivity estimation.
------
With best regards,
Alexander Korotkov.
| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Alexander Korotkov <aekorotkov(at)gmail(dot)com> |
| Cc: | pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Proposal: collect frequency statistics for arrays |
| Date: | 2011-02-18 18:57:55 |
| Message-ID: | 12406.1298055475@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Alexander Korotkov <aekorotkov(at)gmail(dot)com> writes:
> I have following proposal. Currently the ts_typanalyze function accumulates
> frequency statistics for ts_vector using lossy counting technique. But no
> frequency statistics is collecting over arrays. I'm going to generalize
> ts_typanalyze to make it collecting statistics for arrays too. ts_typanalyze
> internally uses lexeme comparison and hashing. I'm going to use functions
> from default btree and hash opclasses of array element type in this
> capacity. Collected frequency statistics for arrays can be used for && and
> @> operators selectivity estimation.
It'd be better to just make a separate function for arrays, instead of
trying to kluge ts_typanalyze to the point where it'd cover both cases.
regards, tom lane
| From: | Alexander Korotkov <aekorotkov(at)gmail(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Proposal: collect frequency statistics for arrays |
| Date: | 2011-02-19 20:43:22 |
| Message-ID: | AANLkTik4FMnhbaRxSY_k7y_j2Xbjzf+uDsaU=g--eSaB@mail.gmail.com |
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| Lists: | pgsql-hackers |
Thanks for feedback on my proposal.
Ok, I'll write it as an separate function. After that I'm going to look if
is there a way to union them without kluge. If I'll not find such way then
I'll propose patch with separate function.
------
With best regards,
Alexander Korotkov.