Port Bug Report: Wild memory use for badly written SQL

============================================================================
                        POSTGRESQL BUG REPORT TEMPLATE
============================================================================


Your name               : Urban Widmark
Your email address      : urban@svenskatest.se

Category                : runtime: back-end: SQL
Severity                : serious

Summary: Wild memory use for badly written SQL

System Configuration
--------------------
  Operating System   : Linux 2.2.x & 2.3.x

  PostgreSQL version : 6.5beta and 6.4.2 (I think)

  Compiler used      : gcc 2.7.2.3

Hardware:
---------
Linux tux.svenskatest.se 2.2.7 #1 Sun May 2 12:04:13 CEST 1999 i586 unknown
Upgraded RedHat 5.0
Pentium, 32M RAM, IDE, eepro 10/100 pci

Versions of other tools:
------------------------
GNU tools (make, flex, ...)

--------------------------------------------------------------------------

Problem Description:
--------------------
Memory usage for the postmaster process is huge (more than
the ~300M virtually available) for a certain SQL statement,
even with empty data tables.

I find it unlikely that it should need that much space to
handle the statement on an empty table.

This is especially bad on systems where the kernel kills a
random process when running out of memory (eg Linux 2.2/2.3).


--------------------------------------------------------------------------

Test Case:
----------
JDBC access to the following table:

Table    = ts_syllabus
|              Field               |              Type                | Length|
+----------------------------------+----------------------------------+-------+
| ts_lang                          | varchar() not null               |    50 |
| ts_key                           | varchar() not null               |    50 |
| ts_val                           | varchar()                        |  2000 |

select * from ts_syllabus where
  (ts_key like '1%' and ts_lang='swe') or
  (ts_key like '2%' and ts_lang='swe') or
  (ts_key like '3%' and ts_lang='swe') or
  (ts_key like '4%' and ts_lang='swe') or
  (ts_key like '5%' and ts_lang='swe') or
  (ts_key like '6%' and ts_lang='swe') or
  (ts_key like '7%' and ts_lang='swe') or
  (ts_key like '8%' and ts_lang='swe') or
  (ts_key like '9%' and ts_lang='swe')


--------------------------------------------------------------------------

Solution:
---------


--------------------------------------------------------------------------