Re: Cache last known per-tuple offsets to speed long tuple

I remaked patch for "Cache last known per-tuple offsets to speed
long tuple access" that is in TODO list.

The point of this patch is as follows:
(1)Add fields to TupleTableSlot and TupleTableData.
This fields are for holding the tuple disassembly information.

(2)Add the codes which initializes/cleans new  fields.
These codes are added to execTuples.c.

(3)Add two functions to execQual.c.
This function name is slot_deformtuple and this is
just like heap_deformtuple. This function can be resumed
from the previous execution using the information
encapsulated in the TupleTableSlot.

Another function is just like heap_getattr and fast_getattr.
This function name is slot_getattr. This is just like
heap_getattr and fast_getattr macro, except it is given a
TupleTableSlot, and this function uses slot_deformtuple
insetead of nocachegetattr.

(4)ExecEvalVar uses new function slot_getattr instead of
heap_getattr.

I executed the test below.
-------------------
Table has 16,384tuples, 200columns. All data type is text.
Table name is aaa. Column name is t001...t200.
Executed SQL is,
select t100, t110, t120, t130, t140, t150,
       t160, t170, t180, t190, t200
from aaa;

The profile result of original code is as follows.
-------------------
Each sample counts as 0.01 seconds.
  %   cumulative   self              self     total
 time   seconds   seconds    calls   s/call   s/call  name
 74.19      1.38     1.38   163846     0.00     0.00  nocachegetattr
  4.30      1.46     0.08   163840     0.00     0.00  FunctionCall3
  1.61      1.49     0.03   397750     0.00     0.00  AllocSetFreeIndex
  1.61      1.52     0.03    16384     0.00     0.00  ExecTargetList
  1.08      1.54     0.02   344152     0.00     0.00  appendBinaryStringInfo

The profile result after the patch applying is as follows.
-------------------
Each sample counts as 0.01 seconds.
  %   cumulative   self              self     total
 time   seconds   seconds    calls  ms/call  ms/call  name
 30.38      0.24     0.24   163840     0.00     0.00  slot_deformtuple
 10.13      0.32     0.08   163840     0.00     0.00  FunctionCall3
  5.06      0.36     0.04   163840     0.00     0.00  slot_getattr
  5.06      0.40     0.04    16384     0.00     0.00  heap_deformtuple
  3.80      0.43     0.03    49159     0.00     0.00  ExecClearTuple

regards,

--- Atsushi Ogawa
a_ogawa@hi-ho.ne.jp