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Add hooks for session start and session end

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These hooks can be used in loadable modules. A simple test module is
included.

Discussion:  https://postgr.es/m/20170720204733.40f2b7eb.nagata@sraoss.co.jp

Fabrízio de Royes Mello  and Yugo Nagata
Reviewed by Michael Paquier and Aleksandr Parfenov
This commit is contained in:
Andrew Dunstan
2017-11-15 10:16:34 -05:00
parent ebc189e122
commit cd8ce3a22c
13 changed files with 233 additions and 0 deletions
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134
src/test/modules/test_session_hooks/test_session_hooks.c Normal file
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/* -------------------------------------------------------------------------
*
* test_session_hooks.c
* Code for testing SESSION hooks.
*
* Copyright (c) 2010-2017, PostgreSQL Global Development Group
*
* IDENTIFICATION
* src/test/modules/test_session_hooks/test_session_hooks.c
*
* -------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/xact.h"
#include "commands/dbcommands.h"
#include "executor/spi.h"
#include "lib/stringinfo.h"
#include "miscadmin.h"
#include "tcop/tcopprot.h"
#include "utils/snapmgr.h"
#include "utils/builtins.h"
PG_MODULE_MAGIC;
/* Entry point of library loading/unloading */
void _PG_init(void);
void _PG_fini(void);
/* GUC variables */
static char *session_hook_username = "postgres";
/* Original Hook */
static session_start_hook_type prev_session_start_hook = NULL;
static session_end_hook_type prev_session_end_hook = NULL;
static void
register_session_hook(const char *hook_at)
{
const char *username;
StartTransactionCommand();
SPI_connect();
PushActiveSnapshot(GetTransactionSnapshot());
username = GetUserNameFromId(GetUserId(), false);
/* Register log just for configured username */
if (!strcmp(username, session_hook_username))
{
const char *dbname;
int ret;
StringInfoData buf;
dbname = get_database_name(MyDatabaseId);
initStringInfo(&buf);
appendStringInfo(&buf, "INSERT INTO session_hook_log (dbname, username, hook_at) ");
appendStringInfo(&buf, "VALUES ('%s', '%s', '%s');",
dbname, username, hook_at);
ret = SPI_exec(buf.data, 0);
if (ret != SPI_OK_INSERT)
elog(ERROR, "SPI_execute failed: error code %d", ret);
}
SPI_finish();
PopActiveSnapshot();
CommitTransactionCommand();
}
/* sample session start hook function */
static void
sample_session_start_hook()
{
/* Hook just normal backends */
if (MyBackendId != InvalidBackendId)
{
(void) register_session_hook("START");
if (prev_session_start_hook)
prev_session_start_hook();
}
}
/* sample session end hook function */
static void
sample_session_end_hook()
{
/* Hook just normal backends */
if (MyBackendId != InvalidBackendId)
{
if (prev_session_end_hook)
prev_session_end_hook();
(void) register_session_hook("END");
}
}
/*
* Module Load Callback
*/
void
_PG_init(void)
{
/* Save Hooks for Unload */
prev_session_start_hook = session_start_hook;
prev_session_end_hook = session_end_hook;
/* Set New Hooks */
session_start_hook = sample_session_start_hook;
session_end_hook = sample_session_end_hook;
/* Load GUCs */
DefineCustomStringVariable("test_session_hooks.username",
"Username to register log on session start or end",
NULL,
&session_hook_username,
"postgres",
PGC_SIGHUP,
0, NULL, NULL, NULL);
}
/*
* Module Unload Callback
*/
void
_PG_fini(void)
{
/* Uninstall Hooks */
session_start_hook = prev_session_start_hook;
session_end_hook = prev_session_end_hook;
}