Subject: Re: Querry correction required
To: pgsql-sql@lists.postgresql.org
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 <CALg-PKCfZOKE1NWnmsartgPvPjypvOb5B+HZ-6q=H0QrFCZmJQ@mail.gmail.com>
From: Thomas Kellerer <shammat@gmx.net>
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Date: Wed, 18 Nov 2020 18:49:23 +0100
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Sachin Kumar schrieb am 18.11.2020 um 18:43:
> Hi Expert,
>
> While running the below mention query on 2 million cards it is taking to=
o much time, say 420 min. is there any way I can reduce the=C2=A0timing..
>
> Please find=C2=A0my query.
>
> UPDATE hk_card_master_test m
> SET "ACCOUNT_NUMBER" =3D v."v_account_number", "ISSUANCE_NUMBER" =3D v."=
v_issuance_number","cron"=3D1
> FROM (
> SELECT h."id",h."CARD_SEQUENCE_NUMBER" ,h."ACCOUNT_NUMBER" ,h."ISSUANCE_=
NUMBER",c."ACCOUNT_NUMBER" v_account_number,c."ISSUANCE_NUMBER" v_issuance=
_number
> FROM
> hk_card_master_test h
> JOIN
> vdaccount_card_bank c
> ON SUBSTR(c."ACCOUNT_NUMBER", 1, 10) =3D h."CARD_SEQUENCE_NUMBER"
> ORDER BY h."id"
> ) AS v
> WHERE m."CARD_SEQUENCE_NUMBER" =3D v."CARD_SEQUENCE_NUMBER";

I also answered that over at the Admin list

I don't think you need the derived table to begin with (which creates an i=
mplicit self-join of the target table):

As far as I can tell, the following would do the same thing:

     UPDATE hk_card_master_test m
       SET "ACCOUNT_NUMBER" =3D v."v_account_number",
           "ISSUANCE_NUMBER" =3D v."v_issuance_number",
           "cron"=3D1
     FROM vdaccount_card_bank v
     WHERE SUBSTR(v."ACCOUNT_NUMBER", 1, 10) =3D m."CARD_SEQUENCE_NUMBER"

You probably want those indexes:

    create index on vdaccount_card_bank ( (SUBSTR("ACCOUNT_NUMBER", 1, 10)=
 );
    create index on hk_card_master_test ("CARD_SEQUENCE_NUMBER");

Unrelated to your question, but using quoted/uppercase identifiers is gene=
rally discouraged in Postgres:

   https://wiki.postgresql.org/wiki/Don't_Do_This#Don.27t_use_upper_case_t=
able_or_column_names

you probably will have a lot less trouble if you get rid of those.

Thomas