On Sun, Dec 26, 2021, at 1:09 PM, Alvaro Herrera wrote: > On 2021-Dec-26, Euler Taveira wrote: > > > On Sat, Dec 25, 2021, at 1:20 AM, Amit Kapila wrote: > > > On Fri, Dec 24, 2021 at 11:04 AM Peter Smith <smithpb2...@gmail.com> > > > wrote: > > > > > > > > So, IMO the PG docs wording for this part should be relaxed a bit. > > > > > > > > e.g. > > > > BEFORE: > > > > + A nullable column in the <literal>WHERE</literal> clause could > > > > cause the > > > > + expression to evaluate to false; avoid using columns without > > > > not-null > > > > + constraints in the <literal>WHERE</literal> clause. > > > > AFTER: > > > > + A nullable column in the <literal>WHERE</literal> clause could > > > > cause the > > > > + expression to evaluate to false. To avoid unexpected results, any > > > > possible > > > > + null values should be accounted for. > > Is this actually correct? I think a null value would cause the > expression to evaluate to null, not false; the issue is that the filter > considers a null value as not matching (right?). Maybe it's better to > spell that out explicitly; both these wordings seem distracting. [Reading it again...] I think it is referring to the pgoutput_row_filter_exec_expr() return. That's not accurate because it is talking about the expression and the expression returns true, false and null. However, the referred function returns only true or false. I agree that we should explictily mention that a null return means the row won't be published.
> You have this elsewhere: > > + If the optional <literal>WHERE</literal> clause is specified, only rows > + that satisfy the <replaceable > class="parameter">expression</replaceable> > + will be published. Note that parentheses are required around the > + expression. It has no effect on <literal>TRUNCATE</literal> commands. > > Maybe this whole thing is clearer if you just say "If the optional WHERE > clause is specified, rows for which the expression returns false or null > will not be published." With that it should be fairly clear what > happens if you have NULL values in the columns used in the expression, > and you can just delete that phrase you're discussing. Your proposal sounds good to me. -- Euler Taveira EDB https://www.enterprisedb.com/
