Obtain table locks as soon as practical during pg_dump.

For some reason, when we (I) added table lock acquisition to pg_dump,
we didn't think about making it happen as soon as possible after the
start of the transaction.  What with subsequent additions, there was
actually quite a lot going on before we got around to that; which sort
of defeats the purpose.  Rearrange the order of calls in dumpSchema()
to close the risk window as much as we easily can.  Back-patch to all
supported branches.

diff --git a/src/bin/pg_dump/common.c b/src/bin/pg_dump/common.c
index 070036ec054fc2e5f93aacf51ab4e2ac7f7781ee..7ea98b396fa6e5891c55686c84508eeb77e0252f 100644 (file)
--- a/src/bin/pg_dump/common.c
+++ b/src/bin/pg_dump/common.c
@@ -91,6 +91,16 @@ getSchemaData(int *numTablesPtr)
                write_msg(NULL, "reading schemas\n");
        nsinfo = getNamespaces(&numNamespaces);
 
+       /*
+        * getTables should be done as soon as possible, so as to minimize the
+        * window between starting our transaction and acquiring per-table locks.
+        * However, we have to do getNamespaces first because the tables get
+        * linked to their containing namespaces during getTables.
+        */
+       if (g_verbose)
+               write_msg(NULL, "reading user-defined tables\n");
+       tblinfo = getTables(&numTables);
+
        if (g_verbose)
                write_msg(NULL, "reading user-defined functions\n");
        funinfo = getFuncs(&numFuncs);
@@ -121,10 +131,6 @@ getSchemaData(int *numTablesPtr)
                write_msg(NULL, "reading user-defined conversions\n");
        convinfo = getConversions(&numConversions);
 
-       if (g_verbose)
-               write_msg(NULL, "reading user-defined tables\n");
-       tblinfo = getTables(&numTables);
-
        if (g_verbose)
                write_msg(NULL, "reading table inheritance information\n");
        inhinfo = getInherits(&numInherits);