to mark a constraint as valid without scanning all the
>> rows.
>>
>
> Most likely your query is not exactly the same as the check constraint.
> Think about NULL and similar.
>
>
>> This operation is really problematic on a production database with heavy
>>
Jian He
The context here is constraints for partitioning as suggested in
documentation
https://www.postgresql.org/docs/current/ddl-partitioning.html#DDL-PARTITIONING-DECLARATIVE-MAINTENANCE
An example constraint from the documentation:
ALTER TABLE measurement_y2008m02 ADD CONSTRAINT y2008m02
C
On Fri, Nov 15, 2024 at 4:38 PM Philip Couling wrote:
>
> Is there a solid reason why adding a check constraint does not use existing
> indexes for validation.
>
can you give an sql example (except not-null)
where indexes can be used for check constraint validation?
i am not sure I understand it
. But
>> AFAIK Theres no way to mark a constraint as valid without scanning all the
>> rows.
>>
>
> Most likely your query is not exactly the same as the check constraint.
> Think about NULL and similar.
>
>
>> This operation is really problematic on a production
FAIK
> Theres no way to mark a constraint as valid without scanning all the rows.
>
Most likely your query is not exactly the same as the check constraint.
Think about NULL and similar.
> This operation is really problematic on a production database with heavy
> IO load.
>
> Is ther
On Thu, 2024-11-14 at 21:33 +, Philip Couling wrote:
> Is there a solid ready why validating check constraints cannot use existing
> indexes?
> If I can prove the constraint is valid so trivially with a SELECT, then why
> can
> Postgres not do the same (or similar)?
I assume
problematic on a production database with heavy IO
load.
Is there a solid ready why validating check constraints cannot use existing
indexes? If I can prove the constraint is valid so trivially with a SELECT,
then why can Postgres not do the same (or similar)?
> On Jun 29, 2021, at 11:02 AM, Ron wrote:
>
> What's an IOS?
An Index Only Scan. See
https://www.postgresql.org/docs/14/indexes-index-only-scans.html
—
Mark Dilger
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
On 6/29/21 12:46 PM, Tom Lane wrote:
Ron writes:
On 6/29/21 11:42 AM, Tom Lane wrote:
If there's a significant difference in relallvisible fractions, that
would point to something different in your VACUUM housekeeping on
the two systems.
Prod is brand new. Loaded on Saturday; we saw this pro
> On Jun 29, 2021, at 10:33 AM, Ron wrote:
>
> Prod is brand new. Loaded on Saturday; we saw this problem on Sunday during
> pre-acceptance. Thus, while running ANALYZE was top of the list of Things To
> Do, running VACUUM was low.
>
> Is that a mistaken belief?
You might want to run VAC
Ron writes:
> On 6/29/21 11:42 AM, Tom Lane wrote:
>> If there's a significant difference in relallvisible fractions, that
>> would point to something different in your VACUUM housekeeping on
>> the two systems.
> Prod is brand new. Loaded on Saturday; we saw this problem on Sunday during
> pre
On 6/29/21 11:42 AM, Tom Lane wrote:
Ron writes:
On 6/29/21 10:41 AM, Michael Lewis wrote:
What's an example query that uses indexes on test and does not on live?
SELECT COUNT(*) FROM sep_info_report_extract;
On prod, there's a list of "Parallel Seq Scan on _partname" records in
the EXPLA
Ron writes:
> On 6/29/21 10:41 AM, Michael Lewis wrote:
>> What's an example query that uses indexes on test and does not on live?
> SELECT COUNT(*) FROM sep_info_report_extract;
> On prod, there's a list of "Parallel Seq Scan on _partname" records in
> the EXPLAIN output, while the test sy
Other than rows being frozen on test (and not on live), I'm not aware of
anything that would push the planner to choose to do an index scan on an
entire table. Maybe someone else will chime in. Or, if you try running
vacuum freeze on live and can verify if that changes the result.
I'm not sure why
On 6/29/21 10:41 AM, Michael Lewis wrote:
Are vacuum and analyze happening regularly on the live system?
Yes. There's a nightly cron job which vacuums those it thinks needs it
(though it's INSERT-heavy), and ditto ANALYZE.
Specifically, I ran ANALYZE on the prod table just before running th
Are vacuum and analyze happening regularly on the live system? What's an
example query that uses indexes on test and does not on live? Does the live
system show poor estimates when executing 'explain analyze select...' and
the test system show semi-accurate row estimates?
50 million seems to be a
Postgresql 12.5
I've got a big (about 50M rows, but 1.4TB because of xml attachments)
partitioned table full of data that we're seeing sequential scans on, even
though there are supporting indices. Will adding CHECK constraints on the
children, which match the partition ranges inf
Thanks Laurenz
This is interesting...b is True
Thanks and regards,
Jitendra
On Wed 11 Nov, 2020, 22:52 Laurenz Albe, wrote:
> On Wed, 2020-11-11 at 11:47 +0100, Tomas Vondra wrote:
> > you may do this, for example:
> >
> > (b it not null and b = true) and (c is not null)
> >
> > Or somethi
On Wed, 2020-11-11 at 11:47 +0100, Tomas Vondra wrote:
> you may do this, for example:
>
> (b it not null and b = true) and (c is not null)
>
> Or something like that.
My (equivalent) suggestion:
b IS TRUE AND c IS NOT NULL
Yours,
Laurenz Albe
--
Cybertec | https://www.cybertec-postgre
Thanks Tomas
Understood... My bad Was just not looking at that aspect
Thanks once again,
Regards,
Jitendra
On Wed, 11 Nov 2020 at 16:17, Tomas Vondra
wrote:
>
> On 11/11/20 10:06 AM, Jitendra Loyal wrote:
> > Thanks Nikolay
> >
> > I read that but is there a way to meet the above requ
On 11/11/20 10:06 AM, Jitendra Loyal wrote:
> Thanks Nikolay
>
> I read that but is there a way to meet the above requirement. And I will
> like to add that IS NULL and IS NOT NULL should evaluate to true/false.
> These operators are made for this and should not be returning NULL.
>
This has n
true), (null, false);
>>
>> This behavior is described in the docs
>> https://www.postgresql.org/docs/current/ddl-constraints.html#DDL-CONSTRAINTS-CHECK-CONSTRAINTS:
>>
>> > It should be noted that a check constraint is satisfied if the check
>> > expression evalu
ps://www.postgresql.org/docs/current/ddl-constraints.html#DDL-CONSTRAINTS-CHECK-CONSTRAINTS
> :
>
> > It should be noted that a check constraint is satisfied if the check
> expression evaluates to true or the null value. Since most expressions will
> evaluate to the null valu
rrent/ddl-constraints.html#DDL-CONSTRAINTS-CHECK-CONSTRAINTS
:
> It should be noted that a check constraint is satisfied if the check
expression evaluates to true or the null value. Since most expressions will
evaluate to the null value if any operand is null, they will not prevent
null values in the constra
st 11. 11. 2020 v 9:38 odesílatel Chris Sterritt
napsal:
>
> On 11/11/2020 06:44, Jitendra Loyal wrote:
>
> Consider this table definition:
> create table t ( i serial, b bool, c bool,
> constraint b_c check ( (b = true and c is
> not null ) or (b is disti
On 11/11/2020 06:44, Jitendra Loyal wrote:
Consider this table definition:
create table t ( i serial, b bool, c bool,
constraint b_c check ( (b = true and c is not
null ) or (b is distinct
from true and c is null) )
constraint b_c check ( (b = true
Consider this table definition:
create table t ( i serial, b bool, c bool,
constraint b_c check ( (b = true and c is
not null ) or (b is distinct
from true and c is null) )
constraint b_c check ( (b = true and c is
not null )
Dinko Papak writes:
> Here are 3 interesting (to me) numbers:
> 1. creating index on expression (func(timestamp)) takes 5 seconds
> 2. creating check constraint on the same expression takes 10 seconds
> 3. adding partition table based on the same expression without check
> expression takes 20 sec
Here are 3 interesting (to me) numbers:
1. creating index on expression (func(timestamp)) takes 5 seconds
2. creating check constraint on the same expression takes 10 seconds
3. adding partition table based on the same expression without check expression
takes 20 seconds (this has been resolved
On 27/03/18 15:44, Paul Jungwirth wrote:
> SELECT c.conname,
> ...
This just does a variation on select * from
information_schema.check_constraints, and has the same issue, that is the the
returned value for the constraint is not what I give when I create it - but
some 'normalised' vers
On 03/27/2018 04:23 AM, Steve Rogerson wrote:
I am trying to add/change a constraint programmatically, but not if it
already exists, and is the same as before.
...
Is there a way of getting the "normalised" version of constraint so decide if
I need to update the constraint if one already exists?
williamI am trying to add/change a constraint programmatically, but not if it
already exists, and is the same as before.
I can so something like (may not be precise ...)
select check_clause from information_schema.check_constraints where
constraint_name = 'my-name'
but this returns that clause
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