On 2013-02-07 11:15:46 -0800, Jeff Janes wrote:
> On Thu, Feb 7, 2013 at 10:09 AM, Pavan Deolasee
> <[email protected]> wrote:
> >
> > Right. I don't have the database handy at this moment, but earlier in
> > the day I ran some queries against it and found that most of the
> > duplicates which are not accessible via indexes have xmin very close
> > to 2100345903. In fact, many of them are from a consecutive range.
>
> Does anyone have suggestions on how to hack the system to make it
> fast-forward the current transaction id? It would certainly make
> testing this kind of thing faster if I could make transaction id
> increment by 100 each time a new one is generated. Then wrap-around
> could be approached in minutes rather than hours.
I had various plpgsql functions to do that, but those still took quite
some time. As I needed it before I just spent some minutes hacking up a
contrib module to do the job.
I doubt it really think it makes sense as a contrib module on its own
though?
postgres=# select * FROM burnxids(500000);select * FROM
burnxids(500000);
burnxids
----------
5380767
(1 row)
Time: 859.807 ms
burnxids
----------
5880767
(1 row)
Time: 717.700 ms
It doesn't really work in a nice way:
if (GetTopTransactionIdIfAny() != InvalidTransactionId)
elog(ERROR, "can't burn xids in a transaction with xid");
for (i = 0; i < nxids; i++)
{
last = GetNewTransactionId(false);
}
/* don't keep xid as assigned */
MyPgXact->xid = InvalidTransactionId;
but it seems to work ;)
Greetings,
Andres Freund
--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
diff --git a/contrib/Makefile b/contrib/Makefile
index 36e6bfe..aca12a7 100644
--- a/contrib/Makefile
+++ b/contrib/Makefile
@@ -54,7 +54,8 @@ SUBDIRS = \
tsearch2 \
unaccent \
vacuumlo \
- worker_spi
+ worker_spi \
+ xidfuncs
ifeq ($(with_openssl),yes)
SUBDIRS += sslinfo
diff --git a/contrib/xidfuncs/Makefile b/contrib/xidfuncs/Makefile
new file mode 100644
index 0000000..6977a3b
--- /dev/null
+++ b/contrib/xidfuncs/Makefile
@@ -0,0 +1,18 @@
+# contrib/xidfuncs/Makefile
+
+MODULE_big = xidfuncs
+OBJS = xidfuncs.o
+
+EXTENSION = xidfuncs
+DATA = xidfuncs--1.0.sql
+
+ifdef USE_PGXS
+PG_CONFIG = pg_config
+PGXS := $(shell $(PG_CONFIG) --pgxs)
+include $(PGXS)
+else
+subdir = contrib/xidfuncs
+top_builddir = ../..
+include $(top_builddir)/src/Makefile.global
+include $(top_srcdir)/contrib/contrib-global.mk
+endif
diff --git a/contrib/xidfuncs/xidfuncs.c b/contrib/xidfuncs/xidfuncs.c
new file mode 100644
index 0000000..e11b4fb
--- /dev/null
+++ b/contrib/xidfuncs/xidfuncs.c
@@ -0,0 +1,50 @@
+/*-------------------------------------------------------------------------
+ * contrib/xidfuncs/xidfuncs.c
+ *
+ * Copyright (c) 2013, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ * contrib/xidfuncs/xidfuncs.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/transam.h"
+#include "access/xact.h"
+#include "funcapi.h"
+#include "storage/proc.h"
+
+PG_MODULE_MAGIC;
+
+PG_FUNCTION_INFO_V1(burnxids);
+
+extern Datum burnxids(PG_FUNCTION_ARGS);
+
+Datum
+burnxids(PG_FUNCTION_ARGS)
+{
+ int nxids = PG_GETARG_INT32(0);
+ int i;
+ TransactionId last;
+
+ if (nxids <= 1)
+ elog(ERROR, "can't burn a negative amount of xids");
+
+ if (nxids > 500000)
+ elog(ERROR, "burning too many xids is dangerous");
+
+ if (GetTopTransactionIdIfAny() != InvalidTransactionId)
+ elog(ERROR, "can't burn xids in a transaction with xid");
+
+ for (i = 0; i < nxids; i++)
+ {
+ last = GetNewTransactionId(false);
+ }
+
+ /* don't keep xid as assigned */
+ MyPgXact->xid = InvalidTransactionId;
+
+ return Int64GetDatum((int64)last);
+}
diff --git a/contrib/xidfuncs/xidfuncs.control b/contrib/xidfuncs/xidfuncs.control
new file mode 100644
index 0000000..bca7194
--- /dev/null
+++ b/contrib/xidfuncs/xidfuncs.control
@@ -0,0 +1,5 @@
+# xidfuncs extension
+comment = 'xid debugging functions'
+default_version = '1.0'
+module_pathname = '$libdir/xidfuncs'
+relocatable = true
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