Stripping white-space in SELECT statments

Hello,

I've encountered a strange behavior in postgres 7.2.1 regarding how psql
handles strings ending with space characters.

If I want to search for records where the first column (artnrgrpmtrln_1)
begins with
'201901 ', our system that uses the database creates the following SQL
statement:

select artnrgrpmtrln_1 from sr where (artnrgrpmtrln_1>='201901 ' and
artnrgrpmtrln_1<='201901 ÿ'

The execution of this statement gives the following resultset, which I
didn't expect. What I wanted was the first 8 records only.

artnrgrpmtrln_1
--------------------------
201901 00R18000 0035C2
201901 00R18005 0035C3
201901 00R18707 007593
201901 00R28541 0030D6
201901 00R40055 0030D8
201901 00R40277T 0030D7
201901 00S00406 0030D9
201901 00SA0200 003662
201901-D00R18000 0035C2
201901-D00R18005 0035C3
201901-D00R18702 008439
201901-D00R18707 007593
201901-D00R28541 0030D6
201901-D00R40055 0030D8
201901-D00R40277T 0030D7
201901-D00S00406 0030D9
201901-D00SA0200 003662
201901JW00R18000 0035C2
201901JW00R18005 0035C3
201901JW00R18707 007593

The Table description is below.

Table "sr"
Column | Type | Modifiers
-----------------+---------------+-----------
artnrgrpmtrln_1 | character(24) |
mangd_2 | character(8) |
enhet_3 | character(1) |
text_4 | character(15) |
start_5 | character(3) |
lageruppd_6 | character(1) |
materialnr_7 | character(8) |
opfoljd_8 | character(3) |
lgst_9 | character(3) |
Indexes: sr_materialnr_7
Unique keys: sr_artnrgrpmtrln_1

This behaviour seems to have changed since postgreSQL v. 7.2, since it works
there. The reason that we don't use 'LIKE 201901 %' is that it don't use
the index sr_artnrgrpmtrln_1 when doing the lookup.

Is there anyone who can explain this behaviour? Could it be that the parser
strips of the whitespaces in '201901 '?

Best Regards,
Tobbe