Thread

1. maybe incorrect regexp_replace behavior in v8.3.4 ?

   Gauthier, Dave <dave.gauthier@intel.com> — 2012-05-16T13:54:23Z

   Hi:
   
   bi_hsx_a0_latest=# select regexp_replace('xxx','^xxx$','abc');
   regexp_replace
   ----------------
   abc
   (1 row)
   expected behavior because there's a match
   
   
   bi_hsx_a0_latest=# select regexp_replace('xxx','^xxxy$','abc');
   regexp_replace
   ----------------
   xxx
   (1 row)
   expected because there is no match (the 'y' in 'xxxy')
   
   
   
   bi_hsx_a0_latest=# select regexp_replace('xxx','^xxxy$',null);
   regexp_replace
   ----------------
   
   (1 row)
   But why did it return null in this case?  I would think no match would leave it 'xxx'.
   
   Thanks in Advance for any help and/or explanation.
   
   
   

2. Re: maybe incorrect regexp_replace behavior in v8.3.4 ?

   Richard Huxton <dev@archonet.com> — 2012-05-16T14:14:06Z

   On 16/05/12 14:54, Gauthier, Dave wrote:
   > bi_hsx_a0_latest=# select regexp_replace('xxx','^xxxy$',null);
   > regexp_replace
   > ----------------
   >
   > (1 row)
   > But why did it return null in this case?  I would think no match would leave it 'xxx'.
   
   If a function is defined as "strict" then any null parameters 
   automatically result in a null result.
   
   And indeed, this:
      SELECT * FROM pg_proc WHERE proname LIKE 'regexp_r%';
   shows pro_isstrict is set to true, as it is for most other function.s
   
   -- 
      Richard Huxton
      Archonet Ltd
   
   

3. Re: maybe incorrect regexp_replace behavior in v8.3.4 ?

   Tom Lane <tgl@sss.pgh.pa.us> — 2012-05-16T14:15:45Z

   "Gauthier, Dave" <dave.gauthier@intel.com> writes:
   > bi_hsx_a0_latest=# select regexp_replace('xxx','^xxxy$',null);
   > regexp_replace
   > ----------------
   >
   > (1 row)
   > But why did it return null in this case?
   
   regexp_replace is strict, so it never even gets called when there's
   a null input.
   
   			regards, tom lane