Hi, Thank you for developing this great feature. I have tested the committed feature. The manual for the pg_set_relation_stats function says the following: "The value of relpages must be greater than or equal to 0"
However, this function seems to accept -1 for the relpages parameter. Below is
an example of execution:
---
postgres=> CREATE TABLE data1(c1 INT PRIMARY KEY, c2 VARCHAR(10));
CREATE TABLE
postgres=> SELECT pg_set_relation_stats('data1', relpages=>-1);
pg_set_relation_stats
-----------------------
t
(1 row)
postgres=> SELECT relname, relpages FROM pg_class WHERE relname='data1';
relname | relpages
---------+----------
data1 | -1
(1 row)
---
The attached patch modifies the pg_set_relation_stats function to work as
described in the manual.
Regards,
Noriyoshi Shinoda
-----Original Message-----
From: Jeff Davis <[email protected]>
Sent: Saturday, October 12, 2024 8:11 AM
To: jian he <[email protected]>; Corey Huinker
<[email protected]>
Cc: Matthias van de Meent <[email protected]>; Bruce Momjian
<[email protected]>; Tom Lane <[email protected]>; Nathan Bossart
<[email protected]>; Magnus Hagander <[email protected]>; Stephen
Frost <[email protected]>; Ashutosh Bapat <[email protected]>;
Peter Smith <[email protected]>; PostgreSQL Hackers
<[email protected]>; Tomas Vondra
<[email protected]>; [email protected]
Subject: Re: Statistics Import and Export
On Mon, 2024-09-23 at 08:57 +0800, jian he wrote:
> newtup = heap_modify_tuple_by_cols(ctup, tupdesc, ncols, replaces,
> nulls);
>
> you just directly declared "bool nulls[3] = {false, false, false};"
Those must be false (not NULL), because in pg_class those are non-NULL
attributes. They must be set to something whenever we update.
> if any of (RELPAGES_ARG, RELTUPLES_ARG, RELALLVISIBLE_ARG) is null,
> should you set that null[position] to true?
If the corresponding SQL argument is NULL, we leave the existing value
unchanged, we don't set it to NULL.
> otherwise, i am confused with the variable nulls.
>
> Looking at other usage of heap_modify_tuple_by_cols, "ncols" cannot be
> dynamic, it should be a fixed value?
> The current implementation works, because the (bool[3] nulls) is
> always false, never changed.
> if nulls becomes {false, false, true} then "ncols" must be 3, cannot
> be 2.
heap_modify_tuple_by_cols() uses ncols to specify the length of the
values/isnull arrays. The "replaces" is an array of attribute numbers to
replace (in contrast to plain heap_modify_tuple(), which uses an array of
booleans).
We are going to replace a maximum of 3 attributes, so the arrays have a maximum
size of 3. Predeclaring the arrays to be 3 elements is just fine even if we
only use the first 1-2 elements -- it avoids a needless heap allocation/free.
Regards,
Jeff Davis
relpages_stat_update_v1.diff
Description: relpages_stat_update_v1.diff
