473,372 Members | 1,236 Online
Bytes | Software Development & Data Engineering Community
Post Job

Home Posts Topics Members FAQ

Join Bytes to post your question to a community of 473,372 software developers and data experts.

bytea, index and like operator

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Hi,

the following I posted already on pgsql-bugs -- perhaps someone has a good
workaround or fix or can say me that I'm wrong?

There seems to be a bug in handling bytea columns with index and the
like-operator.

When an index scan on a bytea column is active, a query with "like" and "%"
in the search doesn't give the correct result: it finds always 0 rows.

At least in 7.3.4. When the FreeBSD Port for 7.4 is ready (yes, why isn't
it ready?), I'll test this again ... ;-)
Look the test here:
select version();
version
---------------------------------------------------------------------
PostgreSQL 7.3.4 on i386-portbld-freebsd4.8, compiled by GCC 2.95.4
begin;
create table test (b bytea);
create index tst_idx on test(b);
insert into test values ('\001abc\006');
insert into test values ('\001xabc\006');
insert into test values ('\001\002abc\006');
insert into test values ('\000\001\002abc\006');
insert into test values ('\002\003abc\006');

select * from test where b like '\001%';
Result:

b
---
(0 Zeilen) [0 rows]
explain analyze select * from test where b like '\001%';
QUERY PLAN
------------------------------------------------------------------------
Index Scan using tst_idx on test (cost=0.00..17.07 rows=5 width=32)
(actual time=0.04..0.04 rows=0 loops=1)
Index Cond: (b = '0'::bytea)
Filter: (b ~~ '\\001%'::bytea)
Total runtime: 0.14 msec
But with seq scan (after vacuuming, creating index later, dropping the
index...) it works as expected:

drop index tst_idx;
online_demo=> select * from test where b like '\001%';
b
-----------------
\001abc\006
\001xabc\006
\001\002abc\006
(3 Zeilen)
explain analyze select * from test where b like '\001%';
QUERY PLAN
------------------------------------------------------------------------
Seq Scan on test (cost=0.00..22.50 rows=5 width=32) (actual
time=0.05..0.08 rows=3 loops=1)
Filter: (b ~~ '\\001%'::bytea)
Total runtime: 0.16 msec
hmmm ...

It seems, that bytea is no good idea for production use?
Ciao
Alvar

- --
** Alvar C.H. Freude -- http://alvar.a-blast.org/
** Berufsverbot? http://odem.org/aktuelles/staatsanwalt.de.html
** ODEM.org-Tour: http://tour.odem.org/
** Informationsgesellschaft: http://www.wsis-koordinierungskreis.de/

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.2.3 (FreeBSD)

iD8DBQE/zkjvOndlH63J86wRAiNGAKCM/PQL1HxJj55WI0ZaUnk/wFazXgCggdIK
N1CiyG/+HtFT4lp4pZpfSD4=
=fa7q
-----END PGP SIGNATURE-----
---------------------------(end of broadcast)---------------------------
TIP 5: Have you checked our extensive FAQ?

http://www.postgresql.org/docs/faqs/FAQ.html

Nov 12 '05 #1
0 2331

This thread has been closed and replies have been disabled. Please start a new discussion.

Similar topics

48
by: Edwin Quijada | last post by:
Hi !! Everybody I am developing app using Delphi and I have a question: I have to save pictures into my database. Each picture has 20 o 30k aprox. What is the way more optimus? That 's table will...
0
by: Jonathan Bartlett | last post by:
Is there an equivalent function for bytea columns that works like lo_import? Alternatively, is there a way to copy from a large object to a bytea column from SQL? Or maybe someone has another...
1
by: Baldur Norddahl | last post by:
Hi, I need to do something like this: select * from sms where message ilike 'foo%'; Message is a bytea field with UTF-8 content. The charset is actually not important for me, it would be...
2
by: Alvar Freude | last post by:
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hi, I want to change a column from text to bytea; since it seems that alter table can't change the column type, i have to add a temporary column...
32
by: David Garamond | last post by:
Are there any drawbacks of using BYTEA for PK compared to using a primitive/atomic data types like INT/SERIAL? (like significant performance hit, peculiar FK behaviour, etc). I plan to use BYTEA...
4
by: David Garamond | last post by:
May I request that connectby() supports BYTEA keys too? My keys are GUID (16-byte stored in BYTEA). In this case, branch_delim does not make sense because the keys should be fixed-length anyway,...
7
by: Dennis Gearon | last post by:
when bytea, text, and varchar(no limit entered) columns are used, do they ALWAYS use an extra table/file? Or do they only do it after a certain size of input? Also, if I wanted to put a *.pdf...
6
by: Egyd Csaba | last post by:
Hi All, I'd like to dump out my database using plain text format. Everything is ok, but the bytea filds. Restoring the dump file (using <<psql -f LO_TRY_INSERT_BYTEA.sql tmp7>>) it sends an...
4
by: Jerry LeVan | last post by:
Hi, I am adding image and large object support in my Cocoa postgresql browser. Are there going to be any enhanced bytea support functions coming along? It seems sorta silly to have to write...
1
by: CloudSolutions | last post by:
Introduction: For many beginners and individual users, requiring a credit card and email registration may pose a barrier when starting to use cloud servers. However, some cloud server providers now...
0
isladogs
by: isladogs | last post by:
The next Access Europe User Group meeting will be on Wednesday 3 Apr 2024 starting at 18:00 UK time (6PM UTC+1) and finishing by 19:30 (7.30PM). In this session, we are pleased to welcome former...
0
by: ryjfgjl | last post by:
In our work, we often need to import Excel data into databases (such as MySQL, SQL Server, Oracle) for data analysis and processing. Usually, we use database tools like Navicat or the Excel import...
0
by: taylorcarr | last post by:
A Canon printer is a smart device known for being advanced, efficient, and reliable. It is designed for home, office, and hybrid workspace use and can also be used for a variety of purposes. However,...
0
by: Charles Arthur | last post by:
How do i turn on java script on a villaon, callus and itel keypad mobile phone
0
by: aa123db | last post by:
Variable and constants Use var or let for variables and const fror constants. Var foo ='bar'; Let foo ='bar';const baz ='bar'; Functions function $name$ ($parameters$) { } ...
0
by: ryjfgjl | last post by:
If we have dozens or hundreds of excel to import into the database, if we use the excel import function provided by database editors such as navicat, it will be extremely tedious and time-consuming...
0
by: ryjfgjl | last post by:
In our work, we often receive Excel tables with data in the same format. If we want to analyze these data, it can be difficult to analyze them because the data is spread across multiple Excel files...
0
BarryA
by: BarryA | last post by:
What are the essential steps and strategies outlined in the Data Structures and Algorithms (DSA) roadmap for aspiring data scientists? How can individuals effectively utilize this roadmap to progress...

By using Bytes.com and it's services, you agree to our Privacy Policy and Terms of Use.

To disable or enable advertisements and analytics tracking please visit the manage ads & tracking page.