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From: James Pang <[email protected]>
To: Tom Lane <[email protected]>
Cc: Laurenz Albe <[email protected]>
Cc: [email protected]
Subject: Re: a lot of session wait on lock relation
Date: Thu, 15 May 2025 21:43:17 +0800
Message-ID: <CAHgTRfcnPeozVRQUutFmhUffr0fhM-VnLARfs-iBSfrur+bmjQ@mail.gmail.com> (raw)
In-Reply-To: <CAHgTRffkd2uUKxsRKvC3hU-Vje9S=JHxN134YkVN_WhYOw45-g@mail.gmail.com>
References: <CAHgTRfdEVMi_YVuq3M4R4uARhXQ8ZgkMid3LhxjFbS+Y+Z_8GQ@mail.gmail.com>
	<[email protected]>
	<[email protected]>
	<CAHgTRffkd2uUKxsRKvC3hU-Vje9S=JHxN134YkVN_WhYOw45-g@mail.gmail.com>

Thanks, we are checking the partition maintain job , we have 12 partitions
, each week one partition there is a default partition attached with this
table and huge rows in default partition too , default partition has
primary key that include partition key (time range based) too.  partition
job detach/drop old partition and add/attach new partition each week.
  when add/attach new partition , with default partition to verify that it
contains no records which should be located in the partition being
attached,  it will full scan or use partition key(part of primary key) scan
instead ?  primary key (columa, partitionkey).

Thanks,

James

James Pang <[email protected]> 於 2025年5月15日週四 下午9:32寫道：

> thanks, we are checking  partition   maintain jobs ,that hold access
> exclusive lock.
>
> Tom Lane <[email protected]> 於 2025年5月15日週四 下午9:24寫道：
>
>> Laurenz Albe <[email protected]> writes:
>> > On Thu, 2025-05-15 at 16:27 +0800, James Pang wrote:
>> >> why inserts into partition table cause "relation lock" ?
>>
>> > Something else does; use the pg_blocking_pids() function with the
>> process ID of
>> > a blocked backend to find out who is holding the lock.
>>
>> More specifically: the inserts are only trying to get a shared lock.
>> If they are blocked, it's because some other operation is already
>> holding an exclusive lock on the table and is not letting go.
>> Look for uncommitted DDL changes.
>>
>> More details about that at [1].
>>
>>                         regards, tom lane
>>
>> [1]
>> https://www.postgresql.org/docs/current/explicit-locking.html#LOCKING-TABLES
>>
>>
>>

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