Re: does update of column with no relation imply a relation check of other column? - Mailing list pgsql-performance

From Tom Lane
Subject Re: does update of column with no relation imply a relation check of other column?
Date
Msg-id 7564.1320090935@sss.pgh.pa.us
Whole thread Raw
In response to Re: does update of column with no relation imply a relation check of other column?  (Robert Haas <robertmhaas@gmail.com>)
List pgsql-performance
Robert Haas <robertmhaas@gmail.com> writes:
> On Wed, Oct 19, 2011 at 12:42 PM, Greg Jaskiewicz <gryzman@gmail.com> wrote:
>> When I do an insert on table B, the database check if value for column
>> �table_a_id� exists in table A
>> But, if I do an update of column �address� of table B, does the database
>> check again?

> I just tested this, and it seems not.

It will not, unless you update the same row more than once in a single
transaction.  If you do that, it no longer has enough information to be
sure the referencing value hasn't changed in that transaction, so it
will do a check.

            regards, tom lane

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