[sqlite] temp files

[Dmytro Bogovych]

Greetings.
I'm trying to run simple update on the following table
CREATE TABLE tree
(
  parent INTEGER,
  child INTEGER,
  number INTEGER,
  children INTEGER
)
The query itself:
update TREE set number = number + 1 where child = ? and parent = ? and  
number > ?

During execution of this query the following func is called:
static int sqlite3pager_opentemp(char *zFile, OsFile *fd)
from pager.c and temporary file is created in my temp directory.
Is it expected behaviour?
May I to use any SQLite's caching to avoid too often creating of temporary  
files?

I'm already using
PRAGMA synchronous = NORMAL
PRAGMA cache_size = 1000
PRAGMA temp_store = MEMORY
--
With best regards,
Dmytro Bogovych