If you are using PostgreSQL for hosting
your Drupal sites, you might have noticed a lot of
warnings in your logs like these:

Aug  8 18:41:05 s002 postgres[90076]: [5-1] WARNING:  nonstandard use of \\ in a string literal at character 32Aug  8 18:41:05 s002 postgres[90076]: [5-2] HINT:  Use the escape string syntax for backslashes, e.g., E'\\'.Aug  8 18:41:05 s002 postgres[90076]: [6-1] WARNING:  nonstandard use of \\ in a string literal at character 122Aug  8 18:41:05 s002 postgres[90076]: [6-2] HINT:  Use the escape string syntax for backslashes, e.g., E'\\'.

The immediate cause for this is
bug #426008 in Drupal core, but the
issue stems from the fact that PostgreSQL does not conform exactly to
the SQL standard with regards to backslashes in strings. The reasoning
behind this and why its going away (as a default setting) in PostgreSQL
9.1 can be read in this excellent blog post by Bruce Momjian.

But how do I fix it?

The good news is that this behavior is configurable. You can set
standard_conforming_strings = on in your postgresql.conf and be done
with it. This will be the default setting from PostgreSQL 9.1, and
hopefully the other applications using your database do not depend on
the legacy behavior (if they do, they need fixing).

If that’s not suitable for your setup, there is a few other suggestions
in this forum thread.