Re: Planner question - "bit" data types

Bruce Momjian wrote:

Alvaro Herrera wrote: 

Karl Denninger escribi?:
   

The individual boolean fields don't kill me and in terms of some of the
application issues they're actually rather easy to code for.

The problem with re-coding for them is extensibility (by those who
install and administer the package); a mask leaves open lots of extra
bits for "site-specific" use, where hard-coding booleans does not, and
since the executable is a binary it instantly becomes a huge problem for
everyone but me.     

Did you try hiding the bitmask operations inside a function as Tom
suggested?   

Yes.  In addition, functions that are part of expression indexes do get
their own optimizer statistics, so it does allow you to get optimizer
stats for your test without having to use booleans.

I see this documented in the 8.0 release notes:
    * "ANALYZE" now collects statistics for expression indexes (Tom)      Expression indexes (also called functional indexes) allow users      to index not just columns but the results of expressions and      function calls. With this release, the optimizer can gather and      use statistics about the contents of expression indexes. This will      greatly improve the quality of planning for queries in which an      expression index is relevant.

Is this in our main documentation somewhere?
 

Interesting... declaring this:

create function ispermitted(text, integer) returns boolean as $$
select permission & $2 = permission from forum where forum.name=$1;
$$ Language SQL STABLE;

then calling it with "ispermitted(post.forum, '4')" as one of the terms causes the query optimizer to treat it as a FILTER instead of a nested loop, and it works as expected.

However, I don't think I can index that - right - since there are two variables involved which are not part of the table being indexed.....

-- Karl