Alvaro Herrera napsal(a):
Zdenek Kotala wrote:
Alvaro Herrera napsal(a):
Simon Riggs wrote:
But perhaps writing a single WAL record if you scan whole page and set
all bits at once. Then it makes sense in some cases.
So this is what I ended up doing; attached.
Please, DO NOT MOVE position of page version in PageHeader structure!
Hmm. The only way I see we could do that is to modify the checksum
struct member to a predefined value before calculating the page's
checksum.
Ah, actually there's another alternative -- leave the checksum on its
current position (start of struct) and move other members below
pg_pagesize_version (leaning towards pd_tli and pd_flags). That'd leave
the page version in the same position.
(Hmm, maybe it's better to move pd_lower and pd_upper?)
No, please, keep pd_lower and pd_upper on same position. They are accessed more
often than pd_tli and pd_flags. It is better for optimization.
By the way, do you need CRC as a first page member? Is it for future development
like CLOG integration into buffers? Why not put it on the end as and mark it as
a special? It will reduce space requirement when CRC is not enabled.
Zdenek
--
Zdenek Kotala Sun Microsystems
Prague, Czech Republic http://sun.com/postgresql
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