Re: row filtering for logical replication

On Mon, Jan 24, 2022 at 10:29 AM Greg Nancarrow <gregn4422(at)gmail(dot)com> wrote:
>
> On Mon, Jan 24, 2022 at 2:47 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> >
> > > (3) pgoutput_row_filter_exec_expr
> > > pgoutput_row_filter_exec_expr() returns false if "isnull" is true,
> > > otherwise (if "isnull" is false) returns the value of "ret"
> > > (true/false).
> > > So the following elog needs to be changed (Peter Smith previously
> > > pointed this out, but it didn't get completely changed):
> > >
> > > BEFORE:
> > > + elog(DEBUG3, "row filter evaluates to %s (isnull: %s)",
> > > + DatumGetBool(ret) ? "true" : "false",
> > > + isnull ? "true" : "false");
> > > AFTER:
> > > + elog(DEBUG3, "row filter evaluates to %s (isnull: %s)",
> > > + isnull ? "false" : DatumGetBool(ret) ? "true" : "false",
> > > + isnull ? "true" : "false");
> > >
> >
> > Do you see any problem with the current? I find the current one easy
> > to understand.
> >
>
> Yes, I see a problem.
>

I tried by inserting NULL value in a column having row filter and the
result it shows is:

LOG: row filter evaluates to false (isnull: true)

This is what is expected.

>
> But regression tests fail when that code change is made (indicating
> that there are cases when "isnull" is true but the function returns
> true instead of false).
>

But that is not what I am seeing in Logs with a test case where the
row filter column has NULL values. Could you please try that see what
is printed in LOG?

You can change the code to make the elevel as LOG to get the results
easily. The test case I tried is as follows:
Node-1:
postgres=# create table t1(c1 int, c2 int);
CREATE TABLE
postgres=# create publication pub for table t1 WHERE (c1 > 10);
CREATE PUBLICATION

Node-2:
postgres=# create table t1(c1 int, c2 int);
CREATE TABLE
postgres=# create subscription sub connection 'dbname=postgres' publication pub;
NOTICE: created replication slot "sub" on publisher
CREATE SUBSCRIPTION

After this on publisher-node, I see the LOG as "LOG: row filter
evaluates to false (isnull: true)". I have verified that in the code
as well (in slot_deform_heap_tuple), we set the value as 0 for isnull
which matches above observation.

--
With Regards,
Amit Kapila.