RE: Parallel copy

Hi Vignesh,

After having a look over the patch,
I have some suggestions for 
0003-Allow-copy-from-command-to-process-data-from-file.patch.

1.

+static uint32
+EstimateCstateSize(ParallelContext *pcxt, CopyState cstate, List *attnamelist,
+                   char **whereClauseStr, char **rangeTableStr,
+                   char **attnameListStr, char **notnullListStr,
+                   char **nullListStr, char **convertListStr)
+{
+    uint32        strsize = MAXALIGN(sizeof(SerializedParallelCopyState));
+
+    strsize += EstimateStringSize(cstate->null_print);
+    strsize += EstimateStringSize(cstate->delim);
+    strsize += EstimateStringSize(cstate->quote);
+    strsize += EstimateStringSize(cstate->escape);


It use function EstimateStringSize to get the strlen of null_print, delim, quote and escape.
But the length of null_print seems has been stored in null_print_len.
And delim/quote/escape must be 1 byte, so I think call strlen again seems unnecessary.

How about  " strsize += sizeof(uint32) + cstate->null_print_len + 1"

2.
+    strsize += EstimateNodeSize(cstate->whereClause, whereClauseStr);

+    copiedsize += CopyStringToSharedMemory(cstate, whereClauseStr,
+                                           shmptr + copiedsize);

Some string length is counted for two times.
The ' whereClauseStr ' has call strlen in EstimateNodeSize once and call strlen in CopyStringToSharedMemory again.
I don't know wheather it's worth to refacor the code to avoid duplicate strlen . what do you think ?

Best regards,
houzj