First of all: thanks a lot for your kind response. Here is the create script for my schema:
CREATE TABLE "app"."archetype_data" (
"id" BIGINT NOT NULL,
"context_id" VARCHAR(1000),
"archetype_name" VARCHAR(1000),
"archetype_path" VARCHAR(1000),
"name" VARCHAR(1000),
"value_string" VARCHAR(1000),
"value_int" BIGINT,
"value_double" DOUBLE PRECISION,
"session_id" VARCHAR(1000),
"instance_index" INTEGER,
CONSTRAINT "archetype_data_pkey" PRIMARY KEY("id")
) WITHOUT OIDS;
Now, regarding your feedback, here are the points, hoping that you can give me feedback, and bring me up to speed in the topic, for I've been in the upper layers of the software world for so long :) Please forgive me for further questions:
Are you telling me that due to name resolution process, my use of variable and column names for context_id and session_id are causing problems? I'll change variable names into names which would be obviously different from column names.
I used the temp table to speed up the following selects, since the actual table has more than 9 million rows. after creating the temp table, I am selecting from 50K rows. Am I wrong about the performance gain here? What would you suggest instead?
Temp tables forced me to use execute, after hitting a known problem, also expressed in the faq, is this what you're talking about?
I will be investing serious time into postgresql from now on, and I hope you can give me couple of useful hints, to ease my way forward :) Looking at the schema, can you think of a better way to send this result set to a java based app?
Many thanks again
Kind regards
Seref
2009/4/22 Filip Rembiałkowski <plk.zuber@xxxxxxxxx>
2009/4/22 sarikan <serefarikan@xxxxxxxxxxxxxxxxxxxxx>
Dear members of the list,
I have a function which returns a custom type, that has only two fields,
each of them being varchar arrays.
The reason that I have written this function is that I have a table
basically with the following structure (with simplified column names)
name_col1 name_col2 sessionId
value1 value3 id1
value2 value2 id1
value4 value4 id1
value7 value4 id2
value2 value2 id2
value4 value4 id2
value1 value5 id3
Why not post your REAL schema? It would make life easier, both for you and for people trying to help.
So mutliple rows are bound together with sessionIds, and I need to get back
all rows with a query, grouped by sessionID. However, group by sql statement
does not solve my problem, since I get back a lot of rows, which I have to
group into objects again in my application. What I need is a way to return
all rows having the same sessionId as a single row. Of course this is not
possible with this table, so I've created a custom type, which has array
type columns. The following function gets all rows that belongs to a
patient, and for each session id, it inserts rows with that session id into
array fields of the custom type.
The problem is, it is very slow! Getting back all the rows with a select
takes 360 ms, while getting back the results of this function takes 50
seconds! Is there any way I can make the following function faster, or any
other methods you can recommend to do what I'm trying to do? I am trying to
avoid hundreds of calls to db, or grouping query results in my middleware
application. Here comes the function, and your help will be much
appreciated.
Best Regards
Seref
(below code edited to be more readable; logic unchanged)
CREATE or REPLACE FUNCTION getNodeContainers( context_Id varchar) RETURNS
setof NodesContainer AS
$$
DECLARE
archetype_data_row app.archetype_data;
archetype_data_row_main app.archetype_data;
nodescontainervar NodesContainer;
session_Id varchar;
indexVar integer := 0;
BEGIN
CREATE TEMP TABLE all_rows_of_patient AS select * from app.archetype_data
WHERE context_id = context_Id;
FOR session_Id IN
SELECT distinct session_id from all_rows_of_patient
LOOP -- do the following for each session_ID
indexVar := 0;
FOR archetype_data_row IN --select rows that belong to this session ID
SELECT * from all_rows_of_patient
WHERE session_id = session_Id and context_id = context_Id
LOOP
nodescontainervar.name[indexVar] := archetype_data_row.name;
nodescontainervar.context_Id[indexVar] := archetype_data_row.context_Id;
indexVar := indexVar + 1;
END LOOP;
return NEXT nodescontainervar;
END LOOP;
drop table all_rows_of_patient;
return;
END;
$$ LANGUAGE 'plpgsql';
please read above code - thats what postgres actually executes. column names have precedence before variable names in name resolution.
conditions like
WHERE context_id = context_Id;
WHERE session_id = session_Id and context_id = context_Id
are obviously no-op conditions, not what you really want.
I hope now it's clear now why this function has long execution time :)
some other remarks:
1) you use temp tables inside a function, which is rather bad (search archives for explanation). try to avoid it.
2) usage of indexvar is not needed - there are array operators and functions
3) if you get rid of temp table, this function could be marked as STABLE,which will prevent penalty in some strange situations
4) mark your function as STRICT, which will save some CPU cycles when someone calls it on null input
HTH.
--
Filip Rembiałkowski
JID,mailto:filip.rembialkowski@xxxxxxxxx
http://filip.rembialkowski.net/
