patch-3 (3-allow-wal-record-header-to-be-split.patch)WAL Format Changes

<div style="direction: ltr;font-family: Tahoma;color: #000000;font-size: 10pt;"><p>While reading patch-3
(3-allow-wal-record-header-to-be-split.patch)of<br /> WAL Format<br /> Changes(<a
href="http://archives.postgresql.org/message-id/4FDA5136.6080206@enterprisedb.com">http://archives.postgresql.org/message-id/4FDA5136.6080206@enterprisedb.com</a>),
Ihad few observations which are summarized below:<br /><br /> 1.<br /> ReadRecord(XLogRecPtr *RecPtr, int emode, bool
fetching_ckpt)<br/> + /*<br /> +  * If we got the whole header already, validate it immediately. Otherwise<br /> +  *
wevalidate it after reading the rest of the header from the next page.<br /> +  */<br /> + if (targetRecOff <=
XLOG_BLCKSZ- SizeOfXLogRecord)<br /> + {<br /> +  if (!ValidXLogRecordHeader(RecPtr, record, emode, randAccess))<br />
+   gotonext_record_is_invalid;<br /> +  gotheader = true;<br /> + }<br /> + else<br /> +  gotheader = false;<br />
+<p>Shouldn'tthe record header validation be done before the check for allocating a bigger record buffer based <br />
ontotal length. Otherwise it may lead to allocation of bigger buffer which may not be required if record header is
invalid.<br/> In cases where record header is not split, validation can be done before otherwise it can be done
later.<p> <p><br/> 3. General observation, not related to your changes <br /> XLogInsert(RmgrId rmid, uint8 info,
XLogRecData*rdata) <br /> . <br /> . <br />         if (freespace == 0) <br />          { <br />                 
updrqst= AdvanceXLInsertBuffer(false); <p><br /> In the code, AdvanceXLInsertBuffer(false); is called after starting
criticalsection and acquiring <br /> WALInsertLock, now if any error occurs inside  AdvanceXLInsertBuffer() <br /> (in
oneof the paths it calls XLogWrite(), from which it can call XLogFileInit() where error can occur); <br /> how will it
releaseWALInsertLock or end critical section. <p> <p> <p>With Regards,<p>Amit Kapila.</div>