Re: [HACKERS] Minor DROP TABLESPACE issue
Tom Lane wrote: Although DROP TABLESPACE can detect tables existing in the target tablespace, it doesn't have any way to detect schemas that reference that tablespace as their default tablespace. Thus you can get implementation-level failures like this one: $ mkdir /tmp/junk regression=# create tablespace junk location '/tmp/junk'; CREATE TABLESPACE regression=# create schema junk tablespace junk; CREATE SCHEMA regression=# drop tablespace junk; DROP TABLESPACE Why this doesn't fail? The junk schema depend on tablespace junk, is there no dependencies between these two objects. G. ---(end of broadcast)--- TIP 9: the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match
Re: [HACKERS] Minor DROP TABLESPACE issue
Gaetano Mendola [EMAIL PROTECTED] writes: is there no dependencies between these two objects. No, and there's little point in adding one, since it wouldn't prevent the problem from happening if you issue the DROP TABLESPACE from a different database. regards, tom lane ---(end of broadcast)--- TIP 9: the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match
[HACKERS] Minor DROP TABLESPACE issue
Although DROP TABLESPACE can detect tables existing in the target tablespace, it doesn't have any way to detect schemas that reference that tablespace as their default tablespace. Thus you can get implementation-level failures like this one: $ mkdir /tmp/junk regression=# create tablespace junk location '/tmp/junk'; CREATE TABLESPACE regression=# create schema junk tablespace junk; CREATE SCHEMA regression=# drop tablespace junk; DROP TABLESPACE regression=# create table junk.foo(f1 text); ERROR: could not create directory /u/pg_data/pg_tablespaces/292909/155056: No such file or directory regression=# The fact that it fails isn't a big problem, but the error message is pretty unclear if you're unfamiliar with the implementation. The same problem would exist with respect to a database's default tablespace, except that a database will always have its system catalogs stored there and so the file-level check prevents dropping the tablespace. I don't think we can directly prevent the DROP TABLESPACE, since we can't see what's in pg_namespace of other databases. I thought about creating a placeholder file associated with every schema that has a nondefault tablespace, thereby allowing the file-level check to detect the problem. But that looks very ugly, not least because namespaces don't have relfilenode values. What might be the most appropriate solution is just to issue a specialized error message in TablespaceCreateDbspace(): if mkdir fails with ENOENT, we could say something like ERROR: tablespace 292909 has been deleted after making an appropriate stat() test to verify that the symlink is indeed gone. It's not great that we'd have to use the OID in this message, but since the pg_tablespace row is (presumably) gone I don't see any way to get the actual name of the tablespace. Anyone see other alternatives? regards, tom lane ---(end of broadcast)--- TIP 1: subscribe and unsubscribe commands go to [EMAIL PROTECTED]
Re: [HACKERS] Minor DROP TABLESPACE issue
On Fri, 18 Jun 2004, Tom Lane wrote: Although DROP TABLESPACE can detect tables existing in the target tablespace, it doesn't have any way to detect schemas that reference that tablespace as their default tablespace. Thus you can get implementation-level failures like this one: Of course. Never thought of that one. The fact that it fails isn't a big problem, but the error message is pretty unclear if you're unfamiliar with the implementation. The same problem would exist with respect to a database's default tablespace, except that a database will always have its system catalogs stored there and so the file-level check prevents dropping the tablespace. Is it really that bad? NamespaceCreate() could just touch a file at pg_tablespaces/tablespaceoid/MyDatabaseId/namespace oid and RemoveSchema() could remove it. Is there anything ugly that I've missed? Gavin ---(end of broadcast)--- TIP 8: explain analyze is your friend
Re: [HACKERS] Minor DROP TABLESPACE issue
On Fri, 18 Jun 2004, Tom Lane wrote: Gavin Sherry [EMAIL PROTECTED] writes: Is it really that bad? NamespaceCreate() could just touch a file at pg_tablespaces/tablespaceoid/MyDatabaseId/namespace oid and RemoveSchema() could remove it. No, because that wouldn't be rollback-safe. You'd have to make the placeholder file act enough like a real relation that the smgr delete-at-commit-or-abort mechanisms could handle it. So then you have to buy into not having its name actually collide with any real relations, which is where I started feeling like I didn't want to pursue that solution. This is certainly doable in theory, it just seems like much more complexity than the problem is worth ... Oh yeah... I forgot about OID wrap around issues and integration into WAL, etc, wouldn't be great fun. If we just wanted to make the error message more user friendly, perhaps we could *gulp* store the tablespace name in PG_VERSION. Then again, all of this can probably be handled better in the manual. Gavin ---(end of broadcast)--- TIP 5: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faqs/FAQ.html
Re: [HACKERS] Minor DROP TABLESPACE issue
On Fri, 18 Jun 2004, Tom Lane wrote: Gavin Sherry [EMAIL PROTECTED] writes: If we just wanted to make the error message more user friendly, perhaps we could *gulp* store the tablespace name in PG_VERSION. That's actually not a bad idea from a debugging standpoint. But I don't see that it helps any for this particular problem. The PG_VERSION file will be gone when we need the info. Duh. I best get some coffee into me. Gavin ---(end of broadcast)--- TIP 3: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly
Re: [HACKERS] Minor DROP TABLESPACE issue
ERROR: tablespace 292909 has been deleted How about schema default tablespace 292909 has been deleted? Chris ---(end of broadcast)--- TIP 3: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly
Re: [HACKERS] Minor DROP TABLESPACE issue
Christopher Kings-Lynne [EMAIL PROTECTED] writes: ERROR: tablespace 292909 has been deleted How about schema default tablespace 292909 has been deleted? Yeah, I was wondering if we could finger the specific schema that was causing the problem, but the place that would detect the error couldn't really know that. Perhaps we could add a HINT advising to look in pg_namespace for the relevant entry. regards, tom lane ---(end of broadcast)--- TIP 4: Don't 'kill -9' the postmaster
