On 15.01.2012 06:49, Alvaro Herrera wrote:
--- 164,178 ---- #define HEAP_HASVARWIDTH 0x0002 /* has variable-width attribute(s) */ #define HEAP_HASEXTERNAL 0x0004 /* has external stored attribute(s) */ #define HEAP_HASOID 0x0008 /* has an object-id field */ ! #define HEAP_XMAX_KEYSHR_LOCK 0x0010 /* xmax is a key-shared locker */ #define HEAP_COMBOCID 0x0020 /* t_cid is a combo cid */ #define HEAP_XMAX_EXCL_LOCK 0x0040 /* xmax is exclusive locker */ ! #define HEAP_XMAX_IS_NOT_UPDATE 0x0080 /* xmax, if valid, is only a locker. ! * Note this is not set unless ! * XMAX_IS_MULTI is also set. */ ! ! #define HEAP_LOCK_BITS (HEAP_XMAX_EXCL_LOCK | HEAP_XMAX_IS_NOT_UPDATE | \ ! HEAP_XMAX_KEYSHR_LOCK) #define HEAP_XMIN_COMMITTED 0x0100 /* t_xmin committed */ #define HEAP_XMIN_INVALID 0x0200 /* t_xmin invalid/aborted */ #define HEAP_XMAX_COMMITTED 0x0400 /* t_xmax committed */
HEAP_XMAX_IS_NOT_UPDATE is a pretty opaque name for that. From the name, I'd say that a DELETE would set that, but the comment says it has to do with locking. After going through all the combinations in my mind, I think I finally understood it: HEAP_XMAX_IS_NOT_UPDATE is set if xmax is a multi-xact, that represent only locking xids, no updates. How about calling it "HEAP_XMAX_LOCK_ONLY", and setting it whenever whether or not xmax is a multi-xid?
- I haven't done anything about exposing FOR KEY UPDATE to the SQL level. There clearly isn't consensus about exposing this; in fact there isn't consensus on exposing FOR KEY SHARE, but I haven't changed that from the previous patch, either.
I think it would be useful to expose it. Not that anyone should be using them in an application (or would it be useful?), but I feel it could make testing significantly easier.
- pg_upgrade bits are missing.
I guess we'll need to rewrite pg_multixact contents in pg_upgrade. Is the page format backwards-compatible?
Why are you renaming HeapTupleHeaderGetXmax() into HeapTupleHeaderGetRawXmax()? Any current callers of HeapTupleHeaderGetXmax() should already check that HEAP_XMAX_IS_MULTI is not set.
-- Heikki Linnakangas EnterpriseDB http://www.enterprisedb.com -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
