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Robert Haas 568d4138c6 Use an MVCC snapshot, rather than SnapshotNow, for catalog scans. ... SnapshotNow scans have the undesirable property that, in the face of concurrent updates, the scan can fail to see either the old or the new versions of the row. In many cases, we work around this by requiring DDL operations to hold AccessExclusiveLock on the object being modified; in some cases, the existing locking is inadequate and random failures occur as a result. This commit doesn't change anything related to locking, but will hopefully pave the way to allowing lock strength reductions in the future. The major issue has held us back from making this change in the past is that taking an MVCC snapshot is significantly more expensive than using a static special snapshot such as SnapshotNow. However, testing of various worst-case scenarios reveals that this problem is not severe except under fairly extreme workloads. To mitigate those problems, we avoid retaking the MVCC snapshot for each new scan; instead, we take a new snapshot only when invalidation messages have been processed. The catcache machinery already requires that invalidation messages be sent before releasing the related heavyweight lock; else other backends might rely on locally-cached data rather than scanning the catalog at all. Thus, making snapshot reuse dependent on the same guarantees shouldn't break anything that wasn't already subtly broken. Patch by me. Review by Michael Paquier and Andres Freund.		12 years ago
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expected	sepgsql: One more getObjectIdentity in lieu of getObjectDescription.	13 years ago
sql	sepgsql: Enforce db_procedure:{execute} permission.	13 years ago
.gitignore	Minor sepgsql regression test fixes.	15 years ago
Makefile	Take sepgsql regression tests out of the regular regression test mechanism.	14 years ago
database.c	sepgql: Use getObjectIdentity rather than getObjectDescription.	13 years ago
dml.c	sepgql: Use getObjectIdentity rather than getObjectDescription.	13 years ago
hooks.c	pgindent run for release 9.3	12 years ago
label.c	Use an MVCC snapshot, rather than SnapshotNow, for catalog scans.	12 years ago
launcher	Update copyrights for 2013	13 years ago
proc.c	pgindent run for release 9.3	12 years ago
relation.c	pgindent run for release 9.3	12 years ago
schema.c	pgindent run for release 9.3	12 years ago
selinux.c	Allow sepgsql labels to depend on object name.	13 years ago
sepgsql-regtest.te	sepgsql: Enforce db_procedure:{execute} permission.	13 years ago
sepgsql.h	sepgsql: Enforce db_procedure:{execute} permission.	13 years ago
sepgsql.sql.in	sepgsql_setcon().	14 years ago
test_sepgsql	sepgsql: Minor improvement to test script, doc fix.	13 years ago
uavc.c	Allow sepgsql labels to depend on object name.	13 years ago