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Commit2cb67c4

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Improve a couple of comments relating to large object snapshot management.
1 parent55233c3 commit2cb67c4

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2 files changed

+12
-15
lines changed

2 files changed

+12
-15
lines changed

‎src/backend/catalog/aclchk.c‎

Lines changed: 6 additions & 11 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/catalog/aclchk.c,v 1.160 2010/01/05 21:53:58 rhaas Exp $
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* $PostgreSQL: pgsql/src/backend/catalog/aclchk.c,v 1.161 2010/01/07 02:41:15 rhaas Exp $
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*
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* NOTES
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* See acl.h.
@@ -3515,16 +3515,11 @@ pg_language_aclmask(Oid lang_oid, Oid roleid,
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/*
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* Exported routine for examining a user's privileges for a largeobject
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*
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* The reason why this interface has an argument of snapshot is that
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* we apply a snapshot available on lo_open(), not SnapshotNow, when
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* it is opened as read-only mode.
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* If we could see the metadata and data from inconsistent viewpoint,
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* it will give us much confusion. So, we need to provide an interface
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* which takes an argument of snapshot.
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*
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* If the caller refers a large object with a certain snapshot except
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* for SnapshotNow, its permission checks should be also applied in
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* the same snapshot.
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* When a large object is opened for reading, it is opened relative to the
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* caller's snapshot, but when it is opened for writing, it is always relative
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* to SnapshotNow, as documented in doc/src/sgml/lobj.sgml. This function
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* takes a snapshot argument so that the permissions check can be made relative
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* to the same snapshot that will be used to read the underlying data.
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*/
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AclMode
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pg_largeobject_aclmask_snapshot(Oidlobj_oid,Oidroleid,

‎src/backend/catalog/pg_largeobject.c‎

Lines changed: 6 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/catalog/pg_largeobject.c,v 1.36 2010/01/02 16:57:36 momjian Exp $
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* $PostgreSQL: pgsql/src/backend/catalog/pg_largeobject.c,v 1.37 2010/01/07 02:41:16 rhaas Exp $
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*
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*-------------------------------------------------------------------------
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*/
@@ -251,9 +251,11 @@ LargeObjectAlterOwner(Oid loid, Oid newOwnerId)
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* We don't use the system cache to for large object metadata, for fear of
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* using too much local memory.
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*
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* Note that LargeObjectExists always scans the system catalog
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* with SnapshotNow, so it is unavailable to use to check
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* existence in read-only accesses.
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* This function always scans the system catalog using SnapshotNow, so it
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* should not be used when a large object is opened in read-only mode (because
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* large objects opened in read only mode are supposed to be viewed relative
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* to the caller's snapshot, whereas in read-write mode they are relative to
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* SnapshotNow).
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*/
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bool
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LargeObjectExists(Oidloid)

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