Thread: fetch_search_path() and elog.c
Hi,
I need to have in the log_line_prefix the search_path where the query
has run.
So last week I've started to read elog.c and I was thinking about a
small patch there using a new "%S" option.
First I've introduced a small code: case 'S': { List *search_path = fetch_search_path(false);
if (search_path != NIL) { ListCell *l; foreach(l, search_path) {
char *nspname;
nspname = get_namespace_name(lfirst_oid(l)); if (nspname)
/*watch out for
deleted namespace */ { appendStringInfo(buf, "%s ", nspname);
pfree(nspname); } }
list_free(search_path); } break; }
but in this way postgres was starting with a core dump writing on log.
Then I've add some code, and now it starts but it kills the postgres
process as soon as a query has sent to log:
$ diff -u elog.c elog_new.c
--- elog.c Sat Mar 12 02:55:15 2005
+++ elog_new.c Sun Jul 10 10:16:35 2005
@@ -67,7 +67,8 @@#include "tcop/tcopprot.h"#include "utils/memutils.h"#include "utils/guc.h"
-
+#include "catalog/namespace.h"
+#include "catalog/pg_type.h"
/* Global variables */ErrorContextCallback *error_context_stack = NULL;
@@ -1444,6 +1445,32 @@ case '%': appendStringInfoChar(buf, '%');
break;
+ /* */
+ case 'S':
+ /* estrae il search_path */
+ if (MyProcPort && (MyProcPort->commandTag !=
NULL)) {
+ char *cmd=MyProcPort->commandTag;
+ if ((strcasecmp(cmd,"SELECT")== 0) ||
(strcasecmp(cmd,"INSERT")== 0) || (strcasecmp(cmd,"UPDATE")== 0) ||
(strcasecmp(cmd,"DELETE")== 0)) {
+
+ }
+ }
+ break;
+List *search_path = fetch_search_path(false);
+ if (search_path != NIL) {
+ ListCell *l;
+ foreach(l, search_path)
+ {
+ char *nspname;
+
+ nspname =
get_namespace_name(lfirst_oid(l));
+ if (nspname) /*
watch out for deleted namespace */
+ {
+ appendStringInfo(buf, "%s ",
nspname);
+ pfree(nspname);
+ }
+ }
+ list_free(search_path);
+ } default: /* format error - ignore
it*/ break;
And here there is the client output:
bash-2.05a$ psql prova -U pgsql
Welcome to psql 8.0.3, the PostgreSQL interactive terminal.
Type: \copyright for distribution terms \h for help with SQL commands \? for help with psql commands \g
orterminate with semicolon to execute query \q to quit
prova=# select * from prova;
server closed the connection unexpectedly This probably means the server terminated abnormally before or
whileprocessing the request.
The connection to the server was lost. Attempting reset: Failed.
!>
Where can I start to understand which checks I've missed and how to gain
the output I need?
Thank you in advance, \ferz
---
NonSoLoSoft - http://www.nonsolosoft.com/
Ferruccio Zamuner <nonsolosoft@diff.org> writes:
> I need to have in the log_line_prefix the search_path where the query
> has run.
> So last week I've started to read elog.c and I was thinking about a
> small patch there using a new "%S" option.
There's no chance of that code working when not inside a transaction;
which means that in most of the scenarios where you really want a log
entry to be made, it will fail.
regards, tom lane
Tom Lane wrote: >Ferruccio Zamuner <nonsolosoft@diff.org> writes: > > >>I need to have in the log_line_prefix the search_path where the query >>has run. >>So last week I've started to read elog.c and I was thinking about a >>small patch there using a new "%S" option. >> >> > >There's no chance of that code working when not inside a transaction; >which means that in most of the scenarios where you really want a log >entry to be made, it will fail. > > regards, tom lane > > Now I've found a simpler solution: case 'S': /* estrae il search_path */ if (namespace_search_path != NULL) appendStringInfo(buf,"%s ", namespace_search_path); break; It seems to work. But I would like to understand why previous code was wrong.
On Mon, Jul 11, 2005 at 06:22:26PM +0200, Ferruccio Zamuner wrote: > Now I've found a simpler solution: > > case 'S': > /* estrae il search_path */ > if (namespace_search_path != NULL) > appendStringInfo(buf, "%s ", namespace_search_path); > break; > > It seems to work. > > But I would like to understand why previous code was wrong. I think it was because you were doing catalog lookups (the get_namespace_name() function, etc), and these don't work outside a transaction. -- Alvaro Herrera (<alvherre[a]alvh.no-ip.org>) "¿Cómo puedes confiar en algo que pagas y que no ves, y no confiar en algo que te dan y te lo muestran?" (Germán Poo)