On 11/14/2014 10:31 AM, Michael Paquier wrote:
> 5) Here why not using the 2nd block instead of the 3rd (@_bt_getroot)?
> + XLogBeginInsert();
> + XLogRegisterBuffer(0, rootbuf, REGBUF_WILL_INIT);
> + XLogRegisterBuffer(2, metabuf, REGBUF_WILL_INIT);
See the comment of the xl_btree_newroot struct. It explains the record
format of the BTREE_NEWROOT record type:
> * Backup Blk 0: new root page (2 tuples as payload, if splitting old root)
> * Backup Blk 1: left child (if splitting an old root)
> * Backup Blk 2: metapage
When _bt_getroot creates a new root, there is no old root, but the same
record type is used in _bt_newroot, which uses block ID 1 to refer to
the old root page.
(Thanks for the comments, again! I'll post a new version soon)
- Heikki