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* How to optimize WHERE column_a IS NOT NULL OR column_b = 'value'
@ 2014-08-11 16:01 Andreas Joseph Krogh <andreas@visena.com>
2014-08-11 18:38 ` Re: How to optimize WHERE column_a IS NOT NULL OR column_b = 'value' Igor Neyman <ineyman@perceptron.com>
2014-08-11 19:34 ` Re: How to optimize WHERE column_a IS NOT NULL OR column_b = 'value' Pavel Stehule <pavel.stehule@gmail.com>
0 siblings, 2 replies; 7+ messages in thread
From: Andreas Joseph Krogh @ 2014-08-11 16:01 UTC (permalink / raw)
To: pgsql-sql
Hi folks, I have the following schema (simplified for this example). create
table folder(id integer primary key, name varchar not null); create table
document(id serial primary key, name varchar not null, owner_id integer not
null, folder_id integer references folder(id)); create index document_owner_idx
ON document(owner_id); create index document_folder_idx ON document(folder_id);
insert into folder(id, name) values(1, 'Folder A'); insert into folder(id,
name) values(2, 'Folder B'); insert into document(name, owner_id, folder_id)
values('Document A', 1, 1); insert into document(name, owner_id, folder_id)
values('Document B', 1, NULL); insert into document(name, owner_id, folder_id)
values('Document C', 2, 2); insert into document(name, owner_id, folder_id)
values('Document D', 2, NULL); select f.id, f.name, doc.id, doc.owner_id,
doc.name FROM document doc left outer join folder f ON doc.folder_id = f.id
WHERE doc.folder_id is not null OR doc.owner_id = 1;
QUERY PLAN
-----------------------------------------------------------------------------------------------------------------------------
Nested Loop Left Join (cost=0.15..13.77 rows=4 width=76) (actual
time=0.031..0.045 rows=3 loops=1)
-> Seq Scan on document doc (cost=0.00..1.05 rows=4 width=44) (actual
time=0.012..0.018 rows=3 loops=1)
Filter: ((folder_id IS NOT NULL) OR (owner_id = 1))
Rows Removed by Filter: 1
-> Index Scan using folder_pkey on folder f (cost=0.15..3.17 rows=1
width=36) (actual time=0.005..0.006 rows=1 loops=3)
Index Cond: (doc.folder_id = id)
Planning time: 0.267 ms
Execution time: 0.094 ms
(8 rows) Is the a way to write a query which uses an index efficiently
for such a schema? I'd like to eliminate the Filter: ((folder_id IS NOT NULL)
OR (owner_id = 1)) and rather have "index cond" insted, is that possible? --
Andreas Joseph Krogh CTO / Partner - Visena AS Mobile: +47 909 56 963
andreas@visena.com <mailto:andreas@visena.com> www.visena.com
<https://www.visena.com; <https://www.visena.com;
^ permalink raw reply [nested|flat] 7+ messages in thread
* Re: How to optimize WHERE column_a IS NOT NULL OR column_b = 'value'
2014-08-11 16:01 How to optimize WHERE column_a IS NOT NULL OR column_b = 'value' Andreas Joseph Krogh <andreas@visena.com>
@ 2014-08-11 18:38 ` Igor Neyman <ineyman@perceptron.com>
1 sibling, 0 replies; 7+ messages in thread
From: Igor Neyman @ 2014-08-11 18:38 UTC (permalink / raw)
To: Andreas Joseph Krogh <andreas@visena.com>; pgsql-sql
From: pgsql-sql-owner@postgresql.org [mailto:pgsql-sql-owner@postgresql.org] On Behalf Of Andreas Joseph Krogh
Sent: Monday, August 11, 2014 12:01 PM
To: pgsql-sql@postgresql.org
Subject: [SQL] How to optimize WHERE column_a IS NOT NULL OR column_b = 'value'
Hi folks,
I have the following schema (simplified for this example).
create table folder(id integer primary key, name varchar not null);
create table document(id serial primary key, name varchar not null, owner_id integer not null, folder_id integer references folder(id));
create index document_owner_idx ON document(owner_id);
create index document_folder_idx ON document(folder_id);
insert into folder(id, name) values(1, 'Folder A');
insert into folder(id, name) values(2, 'Folder B');
insert into document(name, owner_id, folder_id) values('Document A', 1, 1);
insert into document(name, owner_id, folder_id) values('Document B', 1, NULL);
insert into document(name, owner_id, folder_id) values('Document C', 2, 2);
insert into document(name, owner_id, folder_id) values('Document D', 2, NULL);
select f.id, f.name, doc.id, doc.owner_id, doc.name
FROM document doc left outer join folder f ON doc.folder_id = f.id
WHERE doc.folder_id is not null OR doc.owner_id = 1;
QUERY PLAN
-----------------------------------------------------------------------------------------------------------------------------
Nested Loop Left Join (cost=0.15..13.77 rows=4 width=76) (actual time=0.031..0.045 rows=3 loops=1)
-> Seq Scan on document doc (cost=0.00..1.05 rows=4 width=44) (actual time=0.012..0.018 rows=3 loops=1)
Filter: ((folder_id IS NOT NULL) OR (owner_id = 1))
Rows Removed by Filter: 1
-> Index Scan using folder_pkey on folder f (cost=0.15..3.17 rows=1 width=36) (actual time=0.005..0.006 rows=1 loops=3)
Index Cond: (doc.folder_id = id)
Planning time: 0.267 ms
Execution time: 0.094 ms
(8 rows)
Is the a way to write a query which uses an index efficiently for such a schema?
I'd like to eliminate the Filter: ((folder_id IS NOT NULL) OR (owner_id = 1)) and rather have "index cond" insted, is that possible?
--
Andreas Joseph Krogh
CTO / Partner - Visena AS
Mobile: +47 909 56 963
andreas@visena.com<mailto:andreas@visena.com>
www.visena.com<https://www.visena.com;
[cid:image001.png@01CFB571.E24DB8B0]<https://www.visena.com;
You could try partial index on (column_b) where column_a IS NULL.
Regards,
Igor Neyman
Attachments:
[image/png] image001.png (1.9K, ../../A76B25F2823E954C9E45E32FA49D70EC919DE754@mail.corp.perceptron.com/3-image001.png)
download | view image
^ permalink raw reply [nested|flat] 7+ messages in thread
* Re: How to optimize WHERE column_a IS NOT NULL OR column_b = 'value'
2014-08-11 16:01 How to optimize WHERE column_a IS NOT NULL OR column_b = 'value' Andreas Joseph Krogh <andreas@visena.com>
@ 2014-08-11 19:34 ` Pavel Stehule <pavel.stehule@gmail.com>
2014-08-11 19:49 ` Re: How to optimize WHERE column_a IS NOT NULL OR column_b = 'value' SENADIN <senadin2006@yahoo.fr>
2014-08-11 20:19 ` Re: How to optimize WHERE column_a IS NOT NULL OR column_b = 'value' Andreas Joseph Krogh <andreas@visena.com>
1 sibling, 2 replies; 7+ messages in thread
From: Pavel Stehule @ 2014-08-11 19:34 UTC (permalink / raw)
To: Andreas Joseph Krogh <andreas@visena.com>; +Cc: pgsql-sql
Hi
2014-08-11 18:01 GMT+02:00 Andreas Joseph Krogh <andreas@visena.com>:
> Hi folks,
>
> I have the following schema (simplified for this example).
>
> create table folder(id integer primary key, name varchar not null);
>
> create table document(id serial primary key, name varchar not null,
> owner_id integer not null, folder_id integer references folder(id));
> create index document_owner_idx ON document(owner_id);
> create index document_folder_idx ON document(folder_id);
>
> insert into folder(id, name) values(1, 'Folder A');
> insert into folder(id, name) values(2, 'Folder B');
> insert into document(name, owner_id, folder_id) values('Document A', 1,
> 1);
> insert into document(name, owner_id, folder_id) values('Document B', 1,
> NULL);
> insert into document(name, owner_id, folder_id) values('Document C', 2,
> 2);
> insert into document(name, owner_id, folder_id) values('Document D', 2,
> NULL);
>
> select f.id, f.name, doc.id, doc.owner_id, doc.name
> FROM document doc left outer join folder f ON doc.folder_id = f.id
> WHERE doc.folder_id is not null OR doc.owner_id = 1;
>
> QUERY PLAN
>
> -----------------------------------------------------------------------------------------------------------------------------
> Nested Loop Left Join (cost=0.15..13.77 rows=4 width=76) (actual
> time=0.031..0.045 rows=3 loops=1)
> -> Seq Scan on document doc (cost=0.00..1.05 rows=4 width=44) (actual
> time=0.012..0.018 rows=3 loops=1)
> Filter: ((folder_id IS NOT NULL) OR (owner_id = 1))
> Rows Removed by Filter: 1
> -> Index Scan using folder_pkey on folder f (cost=0.15..3.17 rows=1
> width=36) (actual time=0.005..0.006 rows=1 loops=3)
> Index Cond: (doc.folder_id = id)
> Planning time: 0.267 ms
> Execution time: 0.094 ms
> (8 rows)
>
>
> Is the a way to write a query which uses an index efficiently for such a
> schema?
>
> I'd like to eliminate the Filter: ((folder_id IS NOT NULL) OR (owner_id =
> 1)) and rather have "index cond" insted, is that possible?
>
your example is partially broken - ANALYZE and hashjoin and seqscan
penalization are missing - index scan is not used due too small table sizes
I tested 9.5, probably same as 9.4 and there indexes are used
postgres=# set enable_hashjoin to off;
SET
Time: 0.473 ms
postgres=# set enable_seqscan to off;
SET
Time: 0.904 ms
postgres=# explain select f.id, f.name, doc.id, doc.owner_id, doc.name
FROM document doc left outer join folder f ON doc.folder_id = f.id
WHERE doc.folder_id is not null OR doc.owner_id = 1;
QUERY
PLAN
────────────────────────────────────────────────────────────────────────────────────────────────
Merge Left Join (cost=0.26..24.38 rows=3 width=32)
Merge Cond: (doc.folder_id = f.id)
-> Index Scan using document_folder_idx on document doc
(cost=0.13..12.20 rows=3 width=23)
Filter: ((folder_id IS NOT NULL) OR (owner_id = 1))
-> Index Scan using folder_pkey on folder f (cost=0.13..12.16 rows=2
width=13)
Planning time: 0.663 ms
(6 rows)
default 9.2, 9.3, ...
postgres=# explain select f.id, f.name, doc.id, doc.owner_id, doc.name
FROM document doc left outer join folder f ON doc.folder_id = f.id
WHERE doc.folder_id is not null OR doc.owner_id = 1;
QUERY PLAN
─────────────────────────────────────────────────────────────────────
Hash Left Join (cost=1.04..2.12 rows=3 width=32)
Hash Cond: (doc.folder_id = f.id)
-> Seq Scan on document doc (cost=0.00..1.05 rows=3 width=23)
Filter: ((folder_id IS NOT NULL) OR (owner_id = 1))
-> Hash (cost=1.02..1.02 rows=2 width=13)
-> Seq Scan on folder f (cost=0.00..1.02 rows=2 width=13)
(6 rows)
and 9.2 after hashjoin and indexscan penalization
postgres=# explain select f.id, f.name, doc.id, doc.owner_id, doc.name
FROM document doc left outer join folder f ON doc.folder_id = f.id
WHERE doc.folder_id is not null OR doc.owner_id = 1;
QUERY
PLAN
────────────────────────────────────────────────────────────────────────────────────────────────
Merge Left Join (cost=0.00..24.62 rows=3 width=32)
Merge Cond: (doc.folder_id = f.id)
-> Index Scan using document_folder_idx on document doc
(cost=0.00..12.32 rows=3 width=23)
Filter: ((folder_id IS NOT NULL) OR (owner_id = 1))
-> Index Scan using folder_pkey on folder f (cost=0.00..12.28 rows=2
width=13)
(5 rows)
Time: 2.258 ms
What is your PostgreSQL?
Regards
Pavel
P.S. ten years ago I had a similar issue - "OR" predikates can be replaced
by UNION
you can try:
SELECT * FROM
(SELECT * FROM doc
WHERE folder_id IS NOT NULL
UNION
SELECT * FROM doc
WHERE owner_id = 1) s
LEFT JOIN folder ON s.folder_id = folder.id
or some similar magic
select f.id, f.name, doc.id, doc.owner_id, doc.name
FROM document doc left outer join folder f ON doc.folder_id = f.id
WHERE doc.folder_id is not null OR doc.owner_id = 1;
>
> --
> *Andreas Joseph Krogh*
> CTO / Partner - Visena AS
> Mobile: +47 909 56 963
> andreas@visena.com
> www.visena.com
> <https://www.visena.com;
>
^ permalink raw reply [nested|flat] 7+ messages in thread
* Re: How to optimize WHERE column_a IS NOT NULL OR column_b = 'value'
2014-08-11 16:01 How to optimize WHERE column_a IS NOT NULL OR column_b = 'value' Andreas Joseph Krogh <andreas@visena.com>
2014-08-11 19:34 ` Re: How to optimize WHERE column_a IS NOT NULL OR column_b = 'value' Pavel Stehule <pavel.stehule@gmail.com>
@ 2014-08-11 19:49 ` SENADIN <senadin2006@yahoo.fr>
2014-08-11 20:08 ` Re: How to optimize WHERE column_a IS NOT NULL OR column_b = 'value' Andreas Joseph Krogh <andreas@visena.com>
1 sibling, 1 reply; 7+ messages in thread
From: SENADIN @ 2014-08-11 19:49 UTC (permalink / raw)
To: Pavel Stehule <pavel.stehule@gmail.com>; Andreas Joseph Krogh <andreas@visena.com>; +Cc: pgsql-sql
Hello
I am looking for a funtion to calculate the size of a record in a table in a database. Thank you
Anned
Le Lundi 11 août 2014 14h37, Pavel Stehule <pavel.stehule@gmail.com> a écrit :
Hi
2014-08-11 18:01 GMT+02:00 Andreas Joseph Krogh <andreas@visena.com>:
Hi folks,
>
>I have the following schema (simplified for this example).
>
>create table folder(id integer primary key, name varchar not null);
>
>create table document(id serial primary key, name varchar not null, owner_id integer not null, folder_id integer references folder(id));
>create index document_owner_idx ON document(owner_id);
>create index document_folder_idx ON document(folder_id);
>
>insert into folder(id, name) values(1, 'Folder A');
>insert into folder(id, name) values(2, 'Folder B');
>insert into document(name, owner_id, folder_id) values('Document A', 1, 1);
>insert into document(name, owner_id, folder_id) values('Document B', 1, NULL);
>insert into document(name, owner_id, folder_id) values('Document C', 2, 2);
>insert into document(name, owner_id, folder_id) values('Document D', 2, NULL);
>
>select f.id, f.name, doc.id, doc.owner_id, doc.name
>FROM document doc left outer join folder f ON doc.folder_id = f.id
>WHERE doc.folder_id is not null OR doc.owner_id = 1;
>
> QUERY PLAN
>-----------------------------------------------------------------------------------------------------------------------------
> Nested Loop Left Join (cost=0.15..13.77 rows=4 width=76) (actual time=0.031..0.045 rows=3 loops=1)
> -> Seq Scan on document doc (cost=0.00..1.05 rows=4 width=44) (actual time=0.012..0.018 rows=3 loops=1)
> Filter: ((folder_id IS NOT NULL) OR (owner_id = 1))
> Rows Removed by Filter: 1
> -> Index Scan using folder_pkey on folder f (cost=0.15..3.17 rows=1 width=36) (actual time=0.005..0.006 rows=1 loops=3)
> Index Cond: (doc.folder_id = id)
> Planning time: 0.267 ms
> Execution time: 0.094 ms
>(8 rows)
>
>
>Is the a way to write a query which uses an index efficiently for such a schema?
>
>I'd like to eliminate the Filter: ((folder_id IS NOT NULL) OR (owner_id = 1)) and rather have "index cond" insted, is that possible?
your example is partially broken - ANALYZE and hashjoin and seqscan penalization are missing - index scan is not used due too small table sizes
I tested 9.5, probably same as 9.4 and there indexes are used
postgres=# set enable_hashjoin to off;
SET
Time: 0.473 ms
postgres=# set enable_seqscan to off;
SET
Time: 0.904 ms
postgres=# explain select f.id, f.name, doc.id, doc.owner_id, doc.name
FROM document doc left outer join folder f ON doc.folder_id = f.id
WHERE doc.folder_id is not null OR doc.owner_id = 1;
QUERY PLAN
────────────────────────────────────────────────────────────────────────────────────────────────
Merge Left Join (cost=0.26..24.38 rows=3 width=32)
Merge Cond: (doc.folder_id = f.id)
-> Index Scan using document_folder_idx on document doc (cost=0.13..12.20 rows=3 width=23)
Filter: ((folder_id IS NOT NULL) OR (owner_id = 1))
-> Index Scan using folder_pkey on folder f (cost=0.13..12.16 rows=2 width=13)
Planning time: 0.663 ms
(6 rows)
default 9.2, 9.3, ...
postgres=# explain select f.id, f.name, doc.id, doc.owner_id, doc.name
FROM document doc left outer join folder f ON doc.folder_id = f.id
WHERE doc.folder_id is not null OR doc.owner_id = 1;
QUERY PLAN
─────────────────────────────────────────────────────────────────────
Hash Left Join (cost=1.04..2.12 rows=3 width=32)
Hash Cond: (doc.folder_id = f.id)
-> Seq Scan on document doc (cost=0.00..1.05 rows=3 width=23)
Filter: ((folder_id IS NOT NULL) OR (owner_id = 1))
-> Hash (cost=1.02..1.02 rows=2 width=13)
-> Seq Scan on folder f (cost=0.00..1.02 rows=2 width=13)
(6 rows)
and 9.2 after hashjoin and indexscan penalization
postgres=# explain select f.id, f.name, doc.id, doc.owner_id, doc.name
FROM document doc left outer join folder f ON doc.folder_id = f.id
WHERE doc.folder_id is not null OR doc.owner_id = 1;
QUERY PLAN
────────────────────────────────────────────────────────────────────────────────────────────────
Merge Left Join (cost=0.00..24.62 rows=3 width=32)
Merge Cond: (doc.folder_id = f.id)
-> Index Scan using document_folder_idx on document doc (cost=0.00..12.32 rows=3 width=23)
Filter: ((folder_id IS NOT NULL) OR (owner_id = 1))
-> Index Scan using folder_pkey on folder f (cost=0.00..12.28 rows=2 width=13)
(5 rows)
Time: 2.258 ms
What is your PostgreSQL?
Regards
Pavel
P.S. ten years ago I had a similar issue - "OR" predikates can be replaced by UNION
you can try:
SELECT * FROM
(SELECT * FROM doc
WHERE folder_id IS NOT NULL
UNION
SELECT * FROM doc
WHERE owner_id = 1) s
LEFT JOIN folder ON s.folder_id = folder.id
or some similar magic
select f.id, f.name, doc.id, doc.owner_id, doc.name
FROM document doc left outer join folder f ON doc.folder_id = f.id
WHERE doc.folder_id is not null OR doc.owner_id = 1;
>--
>Andreas Joseph Krogh
>CTO / Partner - Visena AS
>Mobile: +47 909 56 963
>andreas@visena.com
>www.visena.com
^ permalink raw reply [nested|flat] 7+ messages in thread
* Re: How to optimize WHERE column_a IS NOT NULL OR column_b = 'value'
2014-08-11 16:01 How to optimize WHERE column_a IS NOT NULL OR column_b = 'value' Andreas Joseph Krogh <andreas@visena.com>
2014-08-11 19:34 ` Re: How to optimize WHERE column_a IS NOT NULL OR column_b = 'value' Pavel Stehule <pavel.stehule@gmail.com>
2014-08-11 19:49 ` Re: How to optimize WHERE column_a IS NOT NULL OR column_b = 'value' SENADIN <senadin2006@yahoo.fr>
@ 2014-08-11 20:08 ` Andreas Joseph Krogh <andreas@visena.com>
0 siblings, 0 replies; 7+ messages in thread
From: Andreas Joseph Krogh @ 2014-08-11 20:08 UTC (permalink / raw)
To: pgsql-sql
Start a new thread På mandag 11. august 2014 kl. 21:49:32, skrev SENADIN <
senadin2006@yahoo.fr <mailto:senadin2006@yahoo.fr>>: Hello I am looking for a
funtion to calculate the size of a record in a table in a database. Thank you
Anned
Le Lundi 11 août 2014 14h37, Pavel Stehule <pavel.stehule@gmail.com> a
écrit : Hi 2014-08-11 18:01 GMT+02:00 Andreas Joseph Krogh <
andreas@visena.com <mailto:andreas@visena.com>>: Hi folks, I have the
following schema (simplified for this example). create table folder(id
integer primary key, name varchar not null); create table document(id serial
primary key, name varchar not null, owner_id integer not null, folder_id
integer references folder(id)); create index document_owner_idx ON
document(owner_id); create index document_folder_idx ON document(folder_id);
insert into folder(id, name) values(1, 'Folder A'); insert into folder(id,
name) values(2, 'Folder B'); insert into document(name, owner_id, folder_id)
values('Document A', 1, 1); insert into document(name, owner_id, folder_id)
values('Document B', 1, NULL); insert into document(name, owner_id, folder_id)
values('Document C', 2, 2); insert into document(name, owner_id, folder_id)
values('Document D', 2, NULL); select f.id <http://f.id/;, f.name
<http://f.name/;, doc.id <http://doc.id/;, doc.owner_id, doc.name
<http://doc.name/; FROM document doc left outer join folder f ON doc.folder_id =
f.id <http://f.id/; WHERE doc.folder_id is not null OR doc.owner_id = 1;
QUERY PLAN
-----------------------------------------------------------------------------------------------------------------------------
Nested Loop Left Join (cost=0.15..13.77 rows=4 width=76) (actual
time=0.031..0.045 rows=3 loops=1)
-> Seq Scan on document doc (cost=0.00..1.05 rows=4 width=44) (actual
time=0.012..0.018 rows=3 loops=1)
Filter: ((folder_id IS NOT NULL) OR (owner_id = 1))
Rows Removed by Filter: 1
-> Index Scan using folder_pkey on folder f (cost=0.15..3.17 rows=1
width=36) (actual time=0.005..0.006 rows=1 loops=3)
Index Cond: (doc.folder_id = id)
Planning time: 0.267 ms
Execution time: 0.094 ms
(8 rows) Is the a way to write a query which uses an index efficiently
for such a schema? I'd like to eliminate the Filter: ((folder_id IS NOT NULL)
OR (owner_id = 1)) and rather have "index cond" insted, is that possible?
your example is partially broken - ANALYZE and hashjoin and seqscan
penalization are missing - index scan is not used due too small table sizes
I tested 9.5, probably same as 9.4 and there indexes are used
postgres=# set enable_hashjoin to off;
SET
Time: 0.473 ms
postgres=# set enable_seqscan to off;
SET
Time: 0.904 ms
postgres=# explain select f.id <http://f.id/;, f.name <http://f.name/;, doc.id
<http://doc.id/;, doc.owner_id, doc.name <http://doc.name/;
FROM document doc left outer join folder f ON doc.folder_id = f.id
<http://f.id/;
WHERE doc.folder_id is not null OR doc.owner_id = 1;
QUERY
PLAN
────────────────────────────────────────────────────────────────────────────────────────────────
Merge Left Join (cost=0.26..24.38 rows=3 width=32)
Merge Cond: (doc.folder_id = f.id <http://f.id/;)
-> Index Scan using document_folder_idx on document doc
(cost=0.13..12.20 rows=3 width=23)
Filter: ((folder_id IS NOT NULL) OR (owner_id = 1))
-> Index Scan using folder_pkey on folder f (cost=0.13..12.16 rows=2
width=13)
Planning time: 0.663 ms
(6 rows)
default 9.2, 9.3, ...
postgres=# explain select f.id <http://f.id/;, f.name <http://f.name/;, doc.id
<http://doc.id/;, doc.owner_id, doc.name <http://doc.name/;
FROM document doc left outer join folder f ON doc.folder_id = f.id
<http://f.id/;
WHERE doc.folder_id is not null OR doc.owner_id = 1;
QUERY PLAN
─────────────────────────────────────────────────────────────────────
Hash Left Join (cost=1.04..2.12 rows=3 width=32)
Hash Cond: (doc.folder_id = f.id <http://f.id/;)
-> Seq Scan on document doc (cost=0.00..1.05 rows=3 width=23)
Filter: ((folder_id IS NOT NULL) OR (owner_id = 1))
-> Hash (cost=1.02..1.02 rows=2 width=13)
-> Seq Scan on folder f (cost=0.00..1.02 rows=2 width=13)
(6 rows)
and 9.2 after hashjoin and indexscan penalization
postgres=# explain select f.id <http://f.id/;, f.name <http://f.name/;, doc.id
<http://doc.id/;, doc.owner_id, doc.name <http://doc.name/;
FROM document doc left outer join folder f ON doc.folder_id = f.id
<http://f.id/;
WHERE doc.folder_id is not null OR doc.owner_id = 1;
QUERY
PLAN
────────────────────────────────────────────────────────────────────────────────────────────────
Merge Left Join (cost=0.00..24.62 rows=3 width=32)
Merge Cond: (doc.folder_id = f.id <http://f.id/;)
-> Index Scan using document_folder_idx on document doc
(cost=0.00..12.32 rows=3 width=23)
Filter: ((folder_id IS NOT NULL) OR (owner_id = 1))
-> Index Scan using folder_pkey on folder f (cost=0.00..12.28 rows=2
width=13)
(5 rows)
Time: 2.258 ms
What is your PostgreSQL?
Regards
Pavel
P.S. ten years ago I had a similar issue - "OR" predikates can be replaced
by UNION
you can try:
SELECT * FROM (SELECT * FROM doc
WHERE folder_id IS NOT NULL UNION SELECT * FROM doc WHERE owner_id = 1)
s LEFT JOIN folder ON s.folder_id = folder.id <http://folder.id/;
or some similar magic select f.id <http://f.id/;, f.name
<http://f.name/;, doc.id <http://doc.id/;, doc.owner_id, doc.name
<http://doc.name/; FROM document doc left outer join folder f ON doc.folder_id =
f.id <http://f.id/; WHERE doc.folder_id is not null OR doc.owner_id = 1;
--Andreas Joseph Krogh CTO / Partner - Visena AS Mobile: +47 909 56 963 <>
andreas@visena.com <mailto:andreas@visena.com> www.visena.com
<https://www.visena.com/; <https://www.visena.com/;
-- Andreas Joseph Krogh CTO / Partner - Visena AS Mobile: +47 909 56
963 andreas@visena.com <mailto:andreas@visena.com> www.visena.com
<https://www.visena.com; <https://www.visena.com;
^ permalink raw reply [nested|flat] 7+ messages in thread
* Re: How to optimize WHERE column_a IS NOT NULL OR column_b = 'value'
2014-08-11 16:01 How to optimize WHERE column_a IS NOT NULL OR column_b = 'value' Andreas Joseph Krogh <andreas@visena.com>
2014-08-11 19:34 ` Re: How to optimize WHERE column_a IS NOT NULL OR column_b = 'value' Pavel Stehule <pavel.stehule@gmail.com>
@ 2014-08-11 20:19 ` Andreas Joseph Krogh <andreas@visena.com>
2014-08-11 20:29 ` Re: How to optimize WHERE column_a IS NOT NULL OR column_b = 'value' Pavel Stehule <pavel.stehule@gmail.com>
1 sibling, 1 reply; 7+ messages in thread
From: Andreas Joseph Krogh @ 2014-08-11 20:19 UTC (permalink / raw)
To: pgsql-sql
På mandag 11. august 2014 kl. 21:34:57, skrev Pavel Stehule <
pavel.stehule@gmail.com <mailto:pavel.stehule@gmail.com>>: Hi 2014-08-11
18:01 GMT+02:00 Andreas Joseph Krogh<andreas@visena.com
<mailto:andreas@visena.com>>: Hi folks, I have the following schema
(simplified for this example). create table folder(id integer primary key,
name varchar not null); create table document(id serial primary key, name
varchar not null, owner_id integer not null, folder_id integer references
folder(id)); create index document_owner_idx ON document(owner_id); create
index document_folder_idx ON document(folder_id); insert into folder(id,
name) values(1, 'Folder A'); insert into folder(id, name) values(2, 'Folder B');
insert into document(name, owner_id, folder_id) values('Document A', 1, 1);
insert into document(name, owner_id, folder_id) values('Document B', 1, NULL);
insert into document(name, owner_id, folder_id) values('Document C', 2, 2);
insert into document(name, owner_id, folder_id) values('Document D', 2, NULL);
select f.id <http://f.id;, f.name <http://f.name;, doc.id <http://doc.id;,
doc.owner_id,doc.name <http://doc.name; FROM document doc left outer join
folder f ON doc.folder_id =f.id <http://f.id; WHERE doc.folder_id is not null
OR doc.owner_id = 1;
QUERY PLAN
-----------------------------------------------------------------------------------------------------------------------------
Nested Loop Left Join (cost=0.15..13.77 rows=4 width=76) (actual
time=0.031..0.045 rows=3 loops=1)
-> Seq Scan on document doc (cost=0.00..1.05 rows=4 width=44) (actual
time=0.012..0.018 rows=3 loops=1)
Filter: ((folder_id IS NOT NULL) OR (owner_id = 1))
Rows Removed by Filter: 1
-> Index Scan using folder_pkey on folder f (cost=0.15..3.17 rows=1
width=36) (actual time=0.005..0.006 rows=1 loops=3)
Index Cond: (doc.folder_id = id)
Planning time: 0.267 ms
Execution time: 0.094 ms
(8 rows) Is the a way to write a query which uses an index efficiently
for such a schema? I'd like to eliminate the Filter: ((folder_id IS NOT NULL)
OR (owner_id = 1)) and rather have "index cond" insted, is that possible?
your example is partially broken - ANALYZE and hashjoin and seqscan
penalization are missing - index scan is not used due too small table sizes
I tested 9.5, probably same as 9.4 and there indexes are used
postgres=# set enable_hashjoin to off;
SET
Time: 0.473 ms
postgres=# set enable_seqscan to off;
SET
Time: 0.904 ms
postgres=# explain select f.id <http://f.id;, f.name <http://f.name;, doc.id
<http://doc.id;, doc.owner_id, doc.name <http://doc.name;
FROM document doc left outer join folder f ON doc.folder_id = f.id
<http://f.id;
WHERE doc.folder_id is not null OR doc.owner_id = 1;
QUERY
PLAN
────────────────────────────────────────────────────────────────────────────────────────────────
Merge Left Join (cost=0.26..24.38 rows=3 width=32)
Merge Cond: (doc.folder_id = f.id <http://f.id;)
-> Index Scan using document_folder_idx on document doc
(cost=0.13..12.20 rows=3 width=23)
Filter: ((folder_id IS NOT NULL) OR (owner_id = 1))
-> Index Scan using folder_pkey on folder f (cost=0.13..12.16 rows=2
width=13)
Planning time: 0.663 ms
(6 rows)
default 9.2, 9.3, ...
postgres=# explain select f.id <http://f.id;, f.name <http://f.name;, doc.id
<http://doc.id;, doc.owner_id, doc.name <http://doc.name;
FROM document doc left outer join folder f ON doc.folder_id = f.id
<http://f.id;
WHERE doc.folder_id is not null OR doc.owner_id = 1;
QUERY PLAN
─────────────────────────────────────────────────────────────────────
Hash Left Join (cost=1.04..2.12 rows=3 width=32)
Hash Cond: (doc.folder_id = f.id <http://f.id;)
-> Seq Scan on document doc (cost=0.00..1.05 rows=3 width=23)
Filter: ((folder_id IS NOT NULL) OR (owner_id = 1))
-> Hash (cost=1.02..1.02 rows=2 width=13)
-> Seq Scan on folder f (cost=0.00..1.02 rows=2 width=13)
(6 rows)
and 9.2 after hashjoin and indexscan penalization
postgres=# explain select f.id <http://f.id;, f.name <http://f.name;, doc.id
<http://doc.id;, doc.owner_id, doc.name <http://doc.name;
FROM document doc left outer join folder f ON doc.folder_id = f.id
<http://f.id;
WHERE doc.folder_id is not null OR doc.owner_id = 1;
QUERY
PLAN
────────────────────────────────────────────────────────────────────────────────────────────────
Merge Left Join (cost=0.00..24.62 rows=3 width=32)
Merge Cond: (doc.folder_id = f.id <http://f.id;)
-> Index Scan using document_folder_idx on document doc
(cost=0.00..12.32 rows=3 width=23)
Filter: ((folder_id IS NOT NULL) OR (owner_id = 1))
-> Index Scan using folder_pkey on folder f (cost=0.00..12.28 rows=2
width=13)
(5 rows)
Time: 2.258 ms
What is your PostgreSQL?
Regards
Pavel
P.S. ten years ago I had a similar issue - "OR" predikates can be replaced
by UNION
you can try:
SELECT * FROM (SELECT * FROM doc
WHERE folder_id IS NOT NULL UNION SELECT * FROM doc WHERE owner_id = 1)
s LEFT JOIN folder ON s.folder_id = folder.id <http://folder.id;
or some similar magic select f.id <http://f.id;, f.name <http://f.name;,
doc.id <http://doc.id;, doc.owner_id, doc.name <http://doc.name; FROM document
doc left outer join folder f ON doc.folder_id =f.id <http://f.id; WHERE
doc.folder_id is not null OR doc.owner_id = 1; I see turning enable_seqscan
to off results in BitmapOr in 9.3: loff=# select version();
version
-------------------------------------------------------------------------------------------------------------
PostgreSQL 9.3.2 on x86_64-unknown-linux-gnu, compiled by gcc (Ubuntu/Linaro
4.8.1-10ubuntu9) 4.8.1, 64-bit
(1 row) loff=# show enable_seqscan ;
enable_seqscan
----------------
off
(1 row) loff=# explain analyze select f.id, f.name, doc.id, doc.owner_id,
doc.name
FROM document doc left outer join folder f ON doc.folder_id = f.id
WHERE doc.folder_id is not null OR doc.owner_id = 1;
QUERY PLAN
--------------------------------------------------------------------------------------------------------------------------------------------
Hash Left Join (cost=103.08..141.89 rows=1095 width=76) (actual
time=0.052..0.057 rows=3 loops=1)
Hash Cond: (doc.folder_id = f.id)
-> Bitmap Heap Scan on document doc (cost=21.10..44.85 rows=1095
width=44) (actual time=0.027..0.028 rows=3 loops=1)
Recheck Cond: ((folder_id IS NOT NULL) OR (owner_id = 1))
-> BitmapOr (cost=21.10..21.10 rows=1100 width=0) (actual
time=0.018..0.018 rows=0 loops=1)
-> Bitmap Index Scan on document_folder_idx
(cost=0.00..16.36 rows=1094 width=0) (actual time=0.012..0.012 rows=2 loops=1)
Index Cond: (folder_id IS NOT NULL)
-> Bitmap Index Scan on document_owner_idx (cost=0.00..4.20
rows=6 width=0) (actual time=0.005..0.005 rows=2 loops=1)
Index Cond: (owner_id = 1)
-> Hash (cost=66.60..66.60 rows=1230 width=36) (actual time=0.011..0.011
rows=2 loops=1)
Buckets: 1024 Batches: 1 Memory Usage: 1kB
-> Index Scan using folder_pkey on folder f (cost=0.15..66.60
rows=1230 width=36) (actual time=0.005..0.006 rows=2 loops=1)
Total runtime: 0.125 ms
(13 rows) In 9.4-beta2 it results in an index-scan with a filter:
andreak=# select version();
version
---------------------------------------------------------------------------------------------------------
PostgreSQL 9.4beta2 on x86_64-unknown-linux-gnu, compiled by gcc (Ubuntu
4.8.2-19ubuntu1) 4.8.2, 64-bit
(1 row) andreak=# show enable_seqscan ;
enable_seqscan
----------------
off
(1 row) andreak=# explain analyze select f.id, f.name, doc.id, doc.owner_id,
doc.name
FROM document doc left outer join folder f ON doc.folder_id = f.id
WHERE doc.folder_id is not null OR doc.owner_id = 1;
QUERY PLAN
-----------------------------------------------------------------------------------------------------------------------------------------
Nested Loop Left Join (cost=0.28..18.92 rows=4 width=76) (actual
time=0.032..0.044 rows=3 loops=1)
-> Index Scan using document_folder_idx on document doc (cost=0.13..6.20
rows=4 width=44) (actual time=0.018..0.024 rows=3 loops=1)
Filter: ((folder_id IS NOT NULL) OR (owner_id = 1))
Rows Removed by Filter: 1
-> Index Scan using folder_pkey on folder f (cost=0.15..3.17 rows=1
width=36) (actual time=0.003..0.004 rows=1 loops=3)
Index Cond: (doc.folder_id = id)
Planning time: 0.260 ms
Execution time: 0.094 ms
(8 rows) I have quite large dataset (and some additional joins) in my
prod-data and hoped that I could solve this with one index-scan on an index on
document-table to avoid 2 index-scans and OR-ing the results. Thanks for help!
-- Andreas Joseph Krogh CTO / Partner - Visena AS Mobile: +47 909 56 963
andreas@visena.com <mailto:andreas@visena.com> www.visena.com
<https://www.visena.com; <https://www.visena.com;
^ permalink raw reply [nested|flat] 7+ messages in thread
* Re: How to optimize WHERE column_a IS NOT NULL OR column_b = 'value'
2014-08-11 16:01 How to optimize WHERE column_a IS NOT NULL OR column_b = 'value' Andreas Joseph Krogh <andreas@visena.com>
2014-08-11 19:34 ` Re: How to optimize WHERE column_a IS NOT NULL OR column_b = 'value' Pavel Stehule <pavel.stehule@gmail.com>
2014-08-11 20:19 ` Re: How to optimize WHERE column_a IS NOT NULL OR column_b = 'value' Andreas Joseph Krogh <andreas@visena.com>
@ 2014-08-11 20:29 ` Pavel Stehule <pavel.stehule@gmail.com>
0 siblings, 0 replies; 7+ messages in thread
From: Pavel Stehule @ 2014-08-11 20:29 UTC (permalink / raw)
To: Andreas Joseph Krogh <andreas@visena.com>; +Cc: pgsql-sql
2014-08-11 22:19 GMT+02:00 Andreas Joseph Krogh <andreas@visena.com>:
> På mandag 11. august 2014 kl. 21:34:57, skrev Pavel Stehule <
> pavel.stehule@gmail.com>:
>
> Hi
>
> 2014-08-11 18:01 GMT+02:00 Andreas Joseph Krogh <andreas@visena.com>:
>>
>> Hi folks,
>>
>> I have the following schema (simplified for this example).
>>
>> create table folder(id integer primary key, name varchar not null);
>>
>> create table document(id serial primary key, name varchar not null,
>> owner_id integer not null, folder_id integer references folder(id));
>> create index document_owner_idx ON document(owner_id);
>> create index document_folder_idx ON document(folder_id);
>>
>> insert into folder(id, name) values(1, 'Folder A');
>> insert into folder(id, name) values(2, 'Folder B');
>> insert into document(name, owner_id, folder_id) values('Document A', 1,
>> 1);
>> insert into document(name, owner_id, folder_id) values('Document B', 1,
>> NULL);
>> insert into document(name, owner_id, folder_id) values('Document C', 2,
>> 2);
>> insert into document(name, owner_id, folder_id) values('Document D', 2,
>> NULL);
>>
>> select f.id, f.name, doc.id, doc.owner_id, doc.name
>> FROM document doc left outer join folder f ON doc.folder_id = f.id
>> WHERE doc.folder_id is not null OR doc.owner_id = 1;
>>
>> QUERY PLAN
>>
>> -----------------------------------------------------------------------------------------------------------------------------
>> Nested Loop Left Join (cost=0.15..13.77 rows=4 width=76) (actual
>> time=0.031..0.045 rows=3 loops=1)
>> -> Seq Scan on document doc (cost=0.00..1.05 rows=4 width=44)
>> (actual time=0.012..0.018 rows=3 loops=1)
>> Filter: ((folder_id IS NOT NULL) OR (owner_id = 1))
>> Rows Removed by Filter: 1
>> -> Index Scan using folder_pkey on folder f (cost=0.15..3.17 rows=1
>> width=36) (actual time=0.005..0.006 rows=1 loops=3)
>> Index Cond: (doc.folder_id = id)
>> Planning time: 0.267 ms
>> Execution time: 0.094 ms
>> (8 rows)
>>
>>
>> Is the a way to write a query which uses an index efficiently for such a
>> schema?
>>
>> I'd like to eliminate the Filter: ((folder_id IS NOT NULL) OR (owner_id =
>> 1)) and rather have "index cond" insted, is that possible?
>>
>
> your example is partially broken - ANALYZE and hashjoin and seqscan
> penalization are missing - index scan is not used due too small table sizes
>
> I tested 9.5, probably same as 9.4 and there indexes are used
>
> postgres=# set enable_hashjoin to off;
> SET
> Time: 0.473 ms
> postgres=# set enable_seqscan to off;
> SET
> Time: 0.904 ms
> postgres=# explain select f.id, f.name, doc.id, doc.owner_id, doc.name
> FROM document doc left outer join folder f ON doc.folder_id = f.id
> WHERE doc.folder_id is not null OR doc.owner_id = 1;
> QUERY
> PLAN
>
> ────────────────────────────────────────────────────────────────────────────────────────────────
> Merge Left Join (cost=0.26..24.38 rows=3 width=32)
> Merge Cond: (doc.folder_id = f.id)
> -> Index Scan using document_folder_idx on document doc
> (cost=0.13..12.20 rows=3 width=23)
> Filter: ((folder_id IS NOT NULL) OR (owner_id = 1))
> -> Index Scan using folder_pkey on folder f (cost=0.13..12.16 rows=2
> width=13)
> Planning time: 0.663 ms
> (6 rows)
>
> default 9.2, 9.3, ...
>
> postgres=# explain select f.id, f.name, doc.id, doc.owner_id, doc.name
> FROM document doc left outer join folder f ON doc.folder_id = f.id
> WHERE doc.folder_id is not null OR doc.owner_id = 1;
> QUERY PLAN
> ─────────────────────────────────────────────────────────────────────
> Hash Left Join (cost=1.04..2.12 rows=3 width=32)
> Hash Cond: (doc.folder_id = f.id)
> -> Seq Scan on document doc (cost=0.00..1.05 rows=3 width=23)
> Filter: ((folder_id IS NOT NULL) OR (owner_id = 1))
> -> Hash (cost=1.02..1.02 rows=2 width=13)
> -> Seq Scan on folder f (cost=0.00..1.02 rows=2 width=13)
> (6 rows)
>
> and 9.2 after hashjoin and indexscan penalization
>
> postgres=# explain select f.id, f.name, doc.id, doc.owner_id, doc.name
> FROM document doc left outer join folder f ON doc.folder_id = f.id
> WHERE doc.folder_id is not null OR doc.owner_id = 1;
> QUERY
> PLAN
>
> ────────────────────────────────────────────────────────────────────────────────────────────────
> Merge Left Join (cost=0.00..24.62 rows=3 width=32)
> Merge Cond: (doc.folder_id = f.id)
> -> Index Scan using document_folder_idx on document doc
> (cost=0.00..12.32 rows=3 width=23)
> Filter: ((folder_id IS NOT NULL) OR (owner_id = 1))
> -> Index Scan using folder_pkey on folder f (cost=0.00..12.28 rows=2
> width=13)
> (5 rows)
>
> Time: 2.258 ms
>
> What is your PostgreSQL?
>
> Regards
>
> Pavel
>
> P.S. ten years ago I had a similar issue - "OR" predikates can be replaced
> by UNION
>
> you can try:
>
> SELECT * FROM
> (SELECT * FROM doc
> WHERE folder_id IS NOT NULL
> UNION
> SELECT * FROM doc
> WHERE owner_id = 1) s
> LEFT JOIN folder ON s.folder_id = folder.id
>
> or some similar magic
>
> select f.id, f.name, doc.id, doc.owner_id, doc.name
> FROM document doc left outer join folder f ON doc.folder_id = f.id
> WHERE doc.folder_id is not null OR doc.owner_id = 1;
>
>
> I see turning enable_seqscan to off results in BitmapOr in 9.3:
>
> loff=# select version();
>
> version
>
> -------------------------------------------------------------------------------------------------------------
> PostgreSQL 9.3.2 on x86_64-unknown-linux-gnu, compiled by gcc
> (Ubuntu/Linaro 4.8.1-10ubuntu9) 4.8.1, 64-bit
> (1 row)
> loff=# show enable_seqscan ;
> enable_seqscan
> ----------------
> off
> (1 row)
> loff=# explain analyze select f.id, f.name, doc.id, doc.owner_id,
> doc.name
>
> FROM document doc left outer join folder f ON doc.folder_id = f.id
> WHERE doc.folder_id is not null OR doc.owner_id = 1;
> QUERY PLAN
>
> --------------------------------------------------------------------------------------------------------------------------------------------
> Hash Left Join (cost=103.08..141.89 rows=1095 width=76) (actual
> time=0.052..0.057 rows=3 loops=1)
>
> Hash Cond: (doc.folder_id = f.id)
> -> Bitmap Heap Scan on document doc (cost=21.10..44.85 rows=1095
> width=44) (actual time=0.027..0.028 rows=3 loops=1)
> Recheck Cond: ((folder_id IS NOT NULL) OR (owner_id = 1))
> -> BitmapOr (cost=21.10..21.10 rows=1100 width=0) (actual
> time=0.018..0.018 rows=0 loops=1)
> -> Bitmap Index Scan on document_folder_idx
> (cost=0.00..16.36 rows=1094 width=0) (actual time=0.012..0.012 rows=2
> loops=1)
> Index Cond: (folder_id IS NOT NULL)
> -> Bitmap Index Scan on document_owner_idx
> (cost=0.00..4.20 rows=6 width=0) (actual time=0.005..0.005 rows=2 loops=1)
> Index Cond: (owner_id = 1)
> -> Hash (cost=66.60..66.60 rows=1230 width=36) (actual
> time=0.011..0.011 rows=2 loops=1)
> Buckets: 1024 Batches: 1 Memory Usage: 1kB
> -> Index Scan using folder_pkey on folder f (cost=0.15..66.60
> rows=1230 width=36) (actual time=0.005..0.006 rows=2 loops=1)
> Total runtime: 0.125 ms
> (13 rows)
>
there is very bad estimation, so some in data is strange
-> Bitmap Index Scan on document_folder_idx
(cost=0.00..16.36 rows=1094 width=0) (actual time=0.012..0.012 rows=2
loops=1)
Index Cond: (folder_id IS NOT NULL)
ensure fresh statistics
>
>
>
> In 9.4-beta2 it results in an index-scan with a filter:
>
> andreak=# select version();
> version
>
> ---------------------------------------------------------------------------------------------------------
> PostgreSQL 9.4beta2 on x86_64-unknown-linux-gnu, compiled by gcc (Ubuntu
> 4.8.2-19ubuntu1) 4.8.2, 64-bit
> (1 row)
> andreak=# show enable_seqscan ;
> enable_seqscan
> ----------------
> off
> (1 row)
> andreak=# explain analyze select f.id, f.name, doc.id, doc.owner_id,
> doc.name
>
> FROM document doc left outer join folder f ON doc.folder_id = f.id
> WHERE doc.folder_id is not null OR doc.owner_id = 1;
> QUERY PLAN
>
> -----------------------------------------------------------------------------------------------------------------------------------------
> Nested Loop Left Join (cost=0.28..18.92 rows=4 width=76) (actual
> time=0.032..0.044 rows=3 loops=1)
> -> Index Scan using document_folder_idx on document doc
> (cost=0.13..6.20 rows=4 width=44) (actual time=0.018..0.024 rows=3 loops=1)
>
> Filter: ((folder_id IS NOT NULL) OR (owner_id = 1))
> Rows Removed by Filter: 1
> -> Index Scan using folder_pkey on folder f (cost=0.15..3.17 rows=1
> width=36) (actual time=0.003..0.004 rows=1 loops=3)
>
> Index Cond: (doc.folder_id = id)
> Planning time: 0.260 ms
>
> Execution time: 0.094 ms
> (8 rows)
>
>
> I have quite large dataset (and some additional joins) in my prod-data and
> hoped that I could solve this with one index-scan on an index on
> document-table to avoid 2 index-scans and OR-ing the results.
>
> Thanks for help!
>
> --
> *Andreas Joseph Krogh*
> CTO / Partner - Visena AS
> Mobile: +47 909 56 963
> andreas@visena.com
> www.visena.com
> <https://www.visena.com;
>
>
^ permalink raw reply [nested|flat] 7+ messages in thread
end of thread, other threads:[~2014-08-11 20:29 UTC | newest]
Thread overview: 7+ messages (download: mbox mbox.gz follow: Atom feed)
-- links below jump to the message on this page --
2014-08-11 16:01 How to optimize WHERE column_a IS NOT NULL OR column_b = 'value' Andreas Joseph Krogh <andreas@visena.com>
2014-08-11 18:38 ` Igor Neyman <ineyman@perceptron.com>
2014-08-11 19:34 ` Pavel Stehule <pavel.stehule@gmail.com>
2014-08-11 19:49 ` SENADIN <senadin2006@yahoo.fr>
2014-08-11 20:08 ` Andreas Joseph Krogh <andreas@visena.com>
2014-08-11 20:19 ` Andreas Joseph Krogh <andreas@visena.com>
2014-08-11 20:29 ` Pavel Stehule <pavel.stehule@gmail.com>
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