Re: [HACKERS] Restrict concurrent update/delete with UPDATE ofpartition key - Mailing list pgsql-hackers

From Amit Kapila
Subject Re: [HACKERS] Restrict concurrent update/delete with UPDATE ofpartition key
Date
Msg-id CAA4eK1LB0bAv4rADwoQSvb7u8evAvVNnume4dqjk_6C5YNajTw@mail.gmail.com
Whole thread Raw
In response to Re: [HACKERS] Restrict concurrent update/delete with UPDATE ofpartition key  (amul sul <sulamul@gmail.com>)
Responses Re: [HACKERS] Restrict concurrent update/delete with UPDATE ofpartition key  (amul sul <sulamul@gmail.com>)
List pgsql-hackers
On Tue, Nov 28, 2017 at 5:58 PM, amul sul <sulamul@gmail.com> wrote:
> On Sat, Nov 25, 2017 at 11:39 AM, Amit Kapila <amit.kapila16@gmail.com> wrote:
>> On Thu, Nov 23, 2017 at 5:18 PM, amul sul <sulamul@gmail.com> wrote:
>>> On Sat, Nov 11, 2017 at 1:05 AM, Robert Haas <robertmhaas@gmail.com> wrote:
>>>> On Wed, Sep 27, 2017 at 7:07 AM, amul sul <sulamul@gmail.com> wrote:
>>>>>
> [...]
>> Few comments:
>>
> Thanks for looking at the patch, please find my comments inline:
>
>> 1.
>> @@ -1480,6 +1493,10 @@ ExecOnConflictUpdate(ModifyTableState *mtstate,
>>   ereport(ERROR,
>>   (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
>>   errmsg("could not serialize access due to concurrent update")));
>> + if (!BlockNumberIsValid(BlockIdGetBlockNumber(&((hufd.ctid).ip_blkid))))
>> + ereport(ERROR,
>> + (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
>> + errmsg("tuple to be updated was already moved to an another
>> partition due to concurrent update")));
>>
>> Why do you think we need this check in the OnConflictUpdate path?  I
>> think we don't it here because we are going to relinquish this version
>> of the tuple and will start again and might fetch some other row
>> version.  Also, we don't support Insert .. On Conflict Update with
>> partitioned tables, see[1], which is also an indication that at the
>> very least we don't need it now.
>>
> Agreed, even though this case will never going to be anytime soon
> shouldn't we have a check for invalid block id? IMHO, we should have
> this check and error report or assert, thoughts?
>

I feel adding code which can't be hit (even if it is error handling)
is not a good idea.  I think having an Assert should be okay, but
please write comments to explain the reason for adding an Assert.

-- 
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com


pgsql-hackers by date:

Previous
From: Michael Paquier
Date:
Subject: Re: [HACKERS] logical decoding of two-phase transactions
Next
From: Michael Paquier
Date:
Subject: Re: [HACKERS] Add Roman numeral conversion to to_number