Re: pg_dump LOCK TABLE ONLY question

Please take it as a very naive and basic approach :-)

What could go wrong here?





diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index 36863df..57a50b5 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -5169,9 +5169,9 @@ getTables(Archive *fout, DumpOptions *dopt, int
*numTables)        * Read-lock target tables to make sure they aren't DROPPED or altered        * in schema before we
getaround to dumping them.        *
 
-        * Note that we don't explicitly lock parents of the target tables; we
-        * assume our lock on the child is enough to prevent schema
-        * alterations to parent tables.
+        * Note that we don't explicitly lock neither parents nor children of
+        * the target tables; we assume our lock on the child is enough to
+        * prevent schema alterations to parent tables.        *        * NOTE: it'd be kinda nice to lock other
relationstoo, not only        * plain tables, but the backend doesn't presently allow that.
 
@@ -5179,11 +5179,18 @@ getTables(Archive *fout, DumpOptions *dopt,
int *numTables)       if (tblinfo[i].dobj.dump && tblinfo[i].relkind == RELKIND_RELATION)       {
resetPQExpBuffer(query);
-           appendPQExpBuffer(query,
-                             "LOCK TABLE %s IN ACCESS SHARE MODE",
-                             fmtQualifiedId(fout->remoteVersion,
-                                       tblinfo[i].dobj.namespace->dobj.name,
-                                            tblinfo[i].dobj.name));
+           if (fout->remoteVersion >= 80400)
+               appendPQExpBuffer(query,
+                               "LOCK TABLE ONLY %s IN ACCESS SHARE MODE",
+                               fmtQualifiedId(fout->remoteVersion,
+
tblinfo[i].dobj.namespace->dobj.name,
+                                               tblinfo[i].dobj.name));
+           else
+               appendPQExpBuffer(query,
+                               "LOCK TABLE %s IN ACCESS SHARE MODE",
+                               fmtQualifiedId(fout->remoteVersion,
+
tblinfo[i].dobj.namespace->dobj.name,
+                                               tblinfo[i].dobj.name));           ExecuteSqlStatement(fout,
query->data);      }
 





On Fri, Oct 16, 2015 at 5:06 PM, Robert Haas <robertmhaas@gmail.com> wrote:
> On Thu, Oct 15, 2015 at 9:13 PM, Jim Nasby <Jim.Nasby@bluetreble.com> wrote:
>> OTOH, now that the catalog is MVCC capable, do we even still need to lock
>> the objects for a schema-only dump?
>
> Yes.  The MVCC snapshots used for catalog reads are stable only for
> the duration of one particular catalog read.  We're not using the
> transaction snapshot.
>
> --
> Robert Haas
> EnterpriseDB: http://www.enterprisedb.com
> The Enterprise PostgreSQL Company