Hi,
I found a mysterious behavior when we use LIKE operator on char(n) data type.
postgres=# select 'abcd'::char(20) LIKE 'ab%cd';?column?
----------f
(1 row)
postgres=# select 'abcd'::char(4) LIKE 'ab%cd';?column?
----------t
(1 row)
LIKE operator (that is eventually processed by textlike) considers the
padding space of char(n) data type as a part of string.
On the other hands, equal operator ignores the padding space when it
compares two strings.
postgres=# select 'abcd'::char(20) = 'abcd';?column?
----------t
(1 row)
postgres=# select 'abcd'::char(4) = 'abcd';?column?
----------t
(1 row)
The LIKE operator on char(n) data type is implemented by textlike().
at pg_proc.h:
DATA(insert OID = 1631 ( bpcharlike PGNSP PGUID 12 1 0 0 0 f f
f f t f i s 2 0 16 "1042 25" _null_ _null_ _null_ _null_ _null_
textlike _null_ _null_ _null_ ));
It calls GenericMatchText() with length of the target string,
calculated by VARSIZE_ANY_EXHDR, however, it includes the padding
space.
It seems to me bcTruelen() gives the correct length for char(n) data
types, instead of this macro.
Is this behavior as expected? or, bug?
Thanks,
--
KaiGai Kohei <kaigai@kaigai.gr.jp>
