Robert Haas wrote:
On Sun, Aug 2, 2009 at 7:57 PM, Tom Lane<t...@sss.pgh.pa.us> wrote:
Robert Haas <robertmh...@gmail.com> writes:
The reason for this regression is that Tom asked me to change
ExplainStmt to just carry a list of nodes and to do all the parsing in
ExplainQuery. Unfortunately, the TupleDesc is constructed by
ExplainResultDesc() which can't trivially be changed to take an
ExplainState, because UtilityTupleDescriptor() also wants to call it.
We could possibly fix this by a hack similar to the one we already
added to GetCommandLogLevel(), but I haven't done that here.
I don't see anything particularly wrong with having ExplainResultDesc
do the same kind of thing GetCommandLogLevel is doing.
After I did this, I thought it would be useful to add a regression
test to make sure that it is doing the right thing. So I came up with
this:
CREATE OR REPLACE FUNCTION test_explain_format(text) RETURNS text AS $$
DECLARE
x RECORD;
BEGIN
EXECUTE 'explain (format ' || $1 || ') select 1' INTO x;
RETURN pg_typeof(x."QUERY PLAN");
END
$$ LANGUAGE plpgsql;
This works the first time you run it in a particular session, but then
if change $1 so as to get a different answer, it fails:
rhaas=# select test_explain_format('text');
test_explain_format
---------------------
text
(1 row)
rhaas=# select test_explain_format('xml');
ERROR: type of "x.QUERY PLAN" does not match that when preparing the plan
CONTEXT: PL/pgSQL function "test_explain_format" line 5 at RETURN
rhaas=# discard
ALL PLANS TEMP
rhaas=# discard plans;
DISCARD PLANS
rhaas=# select test_explain_format('xml');
ERROR: type of "x.QUERY PLAN" does not match that when preparing the plan
CONTEXT: PL/pgSQL function "test_explain_format" line 5 at RETURN
rhaas=# discard all;
DISCARD ALL
rhaas=# select test_explain_format('xml');
ERROR: type of "x.QUERY PLAN" does not match that when preparing the plan
CONTEXT: PL/pgSQL function "test_explain_format" line 5 at RETURN
rhaas=#
If I quit psql and start back up again, then it works:
rhaas=# select test_explain_format('xml');
test_explain_format
---------------------
xml
(1 row)
So I guess that leads me to -
(1) How do I make this work?
(2) Is it worth making this work?
You could have the function create an inner function which it then runs
and drops. I have had to perform such gymnastics in the past to get
around similar problems. And yes, it's ugly as hell.
cheers
andrew
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