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postgres_fdw: Allow postgres_fdw.application_name to include escape sequences.

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application_name that used when postgres_fdw establishes a connection to
a foreign server can be specified in either or both a connection parameter
of a server object and GUC postgres_fdw.application_name. This commit
allows those parameters to include escape sequences that begins with
% character. Then postgres_fdw replaces those escape sequences with
status information. For example, %d and %u are replaced with user name
and database name in local server, respectively. This feature enables us
to add information more easily to track remote transactions or queries,
into application_name of a remote connection.

Author: Hayato Kuroda
Reviewed-by: Kyotaro Horiguchi, Masahiro Ikeda, Hou Zhijie, Fujii Masao
Discussion: https://postgr.es/m/TYAPR01MB5866FAE71C66547C64616584F5EB9@TYAPR01MB5866.jpnprd01.prod.outlook.com
Discussion: https://postgr.es/m/TYCPR01MB5870D1E8B949DAF6D3B84E02F5F29@TYCPR01MB5870.jpnprd01.prod.outlook.com
This commit is contained in:
Fujii Masao
2021-12-24 16:55:11 +09:00
parent 94226d4506
commit 6e0cb3dec1
6 changed files with 218 additions and 1 deletions
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36
contrib/postgres_fdw/connection.c
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@ -348,6 +348,7 @@ connect_pg_server(ForeignServer *server, UserMapping *user)
{
const char **keywords;
const char **values;
char *appname = NULL;
int n;
/*
@ -383,6 +384,39 @@ connect_pg_server(ForeignServer *server, UserMapping *user)
n++;
}
/*
* Search the parameter arrays to find application_name setting, and
* replace escape sequences in it with status information if found.
* The arrays are searched backwards because the last value is used if
* application_name is repeatedly set.
*/
for (int i = n - 1; i >= 0; i--)
{
if (strcmp(keywords[i], "application_name") == 0 &&
*(values[i]) != '\0')
{
/*
* Use this application_name setting if it's not empty string
* even after any escape sequences in it are replaced.
*/
appname = process_pgfdw_appname(values[i]);
if (appname[0] != '\0')
{
values[i] = appname;
break;
}
/*
* This empty application_name is not used, so we set
* values[i] to NULL and keep searching the array to find the
* next one.
*/
values[i] = NULL;
pfree(appname);
appname = NULL;
}
}
/* Use "postgres_fdw" as fallback_application_name */
keywords[n] = "fallback_application_name";
values[n] = "postgres_fdw";
@ -452,6 +486,8 @@ connect_pg_server(ForeignServer *server, UserMapping *user)
/* Prepare new session for use */
configure_remote_session(conn);
if (appname != NULL)
pfree(appname);
pfree(keywords);
pfree(values);
}