Re: Performance Improvement by reducing WAL for Update Operation

Hello, I looked into the patch and have some comments.

From the restriction of the time for this rather big patch,
please excuse that these comments are on a part of it. Others
will follow in few days.

==== heaptuple.c

noncachegetattr(_with_len):

- att_getlength should do strlen as worst case or VARSIZE_ANY
which is heavier than doing one comparizon, so I recommend to
add 'if (len)' as the restriction for doing this, and give NULL
as &len to nocachegetattr_with_len in nocachegetattr.

heap_attr_get_length_and_check_equals:

- Size seems to be used conventionary as the type for memory
object length, so it might be better using Size instead of
int32 as the type for *tup[12]_attr_len in parameter.

- This function returns always false for attrnum <= 0 as whole
tuple or some system attrs comparison regardless of the real
result, which is a bit different from the anticipation which
the name gives. If you need to keep this optimization, it
should have the name more specific to the purpose.

haap_delta_encode:

- Some misleading variable names (like match_not_found),
some reatitions of similiar codelets (att_align_pointer, pglz_out_tag),
misleading slight difference of the meanings of variables of
similar names(old_off and new_off and the similar pairs),
and bit tricky use of pglz_out_add and pglz_out_tag with length = 0.

These are welcome to be modified for better readability.

==== heapam.c

fastgetattr_with_len

- Missing left paren in the line 867 ('nocachegetattr_with_len(tup)...')

- Missing enclosing paren in heapam.c:879 (len, only on style)

- Allowing len = NULL will be good for better performance, like
noncachegetattr.

fastgetattr

- I suppose that the coding covension here is that macro and
alternative c-code are expected to be look similar. fastgetattr
looks quite differ to corresponding macro.

...

regards,

--
Kyotaro Horiguchi
NTT Open Source Software Center