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Make identity sequence management more robust

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Some code could get confused when certain catalog state involving both
identity and serial sequences was present, perhaps during an attempt
to upgrade the latter to the former.  Specifically, dropping the
default of a serial column maintains the ownership of the sequence by
the column, and so it would then be possible to afterwards make the
column an identity column that would now own two sequences.  This
causes the code that looks up the identity sequence to error out,
making the new identity column inoperable until the ownership of the
previous sequence is released.

To fix this, make the identity sequence lookup only consider sequences
with the appropriate dependency type for an identity sequence, so it
only ever finds one (unless something else is broken).  In the above
example, the old serial sequence would then be ignored.  Reorganize
the various owned-sequence-lookup functions a bit to make this
clearer.

Reported-by: Laurenz Albe <laurenz.albe@cybertec.at>
Discussion: https://www.postgresql.org/message-id/flat/470c54fc8590be4de0f41b0d295fd6390d5e8a6c.camel@cybertec.at
This commit is contained in:
Peter Eisentraut
2019-07-22 12:05:03 +02:00
parent efdcca55a3
commit 19781729f7
7 changed files with 48 additions and 20 deletions
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33
src/backend/catalog/pg_depend.c
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@@ -705,10 +705,11 @@ sequenceIsOwned(Oid seqId, char deptype, Oid *tableId, int32 *colId)
/*
* Collect a list of OIDs of all sequences owned by the specified relation,
* and column if specified.
* and column if specified. If deptype is not zero, then only find sequences
* with the specified dependency type.
*/
List *
getOwnedSequences(Oid relid, AttrNumber attnum)
static List *
getOwnedSequences_internal(Oid relid, AttrNumber attnum, char deptype)
{
List *result = NIL;
Relation depRel;
@@ -750,7 +751,8 @@ getOwnedSequences(Oid relid, AttrNumber attnum)
(deprec->deptype == DEPENDENCY_AUTO || deprec->deptype == DEPENDENCY_INTERNAL) &&
get_rel_relkind(deprec->objid) == RELKIND_SEQUENCE)
{
result = lappend_oid(result, deprec->objid);
if (!deptype || deprec->deptype == deptype)
result = lappend_oid(result, deprec->objid);
}
}
@@ -762,17 +764,32 @@ getOwnedSequences(Oid relid, AttrNumber attnum)
}
/*
* Get owned sequence, error if not exactly one.
* Collect a list of OIDs of all sequences owned (identity or serial) by the
* specified relation.
*/
List *
getOwnedSequences(Oid relid)
{
return getOwnedSequences_internal(relid, 0, 0);
}
/*
* Get owned identity sequence, error if not exactly one.
*/
Oid
getOwnedSequence(Oid relid, AttrNumber attnum)
getIdentitySequence(Oid relid, AttrNumber attnum, bool missing_ok)
{
List *seqlist = getOwnedSequences(relid, attnum);
List *seqlist = getOwnedSequences_internal(relid, attnum, DEPENDENCY_INTERNAL);
if (list_length(seqlist) > 1)
elog(ERROR, "more than one owned sequence found");
else if (list_length(seqlist) < 1)
elog(ERROR, "no owned sequence found");
{
if (missing_ok)
return InvalidOid;
else
elog(ERROR, "no owned sequence found");
}
return linitial_oid(seqlist);
}