Support worker_spi to execute the function dynamically.

[Masahiro Ikeda]

Hi,

While I'm working on the thread[1], I found that the function of
worker_spi module fails if 'shared_preload_libraries' doesn't have
worker_spi.
The reason is that the database name is NULL because the database name
is initialized only when process_shared_preload_libraries_in_progress
is true.

```
psql=# SELECT worker_spi_launch(1) ;
2023-07-20 11:00:56.491 JST [1179891] LOG:  worker_spi worker 1 
initialized with schema1.counted
2023-07-20 11:00:56.491 JST [1179891] FATAL:  cannot read pg_class 
without having selected a database at character 22
2023-07-20 11:00:56.491 JST [1179891] QUERY:  select count(*) from 
pg_namespace where nspname = 'schema1'
2023-07-20 11:00:56.491 JST [1179891] STATEMENT:  select count(*) from 
pg_namespace where nspname = 'schema1'
2023-07-20 11:00:56.492 JST [1179095] LOG:  background worker 
"worker_spi" (PID 1179891) exited with exit code 1
```

In my understanding, the restriction is not required. So, I think it's
better to change the behavior.
(v1-0001-Support-worker_spi-to-execute-the-function-dynamical.patch)

What do you think?

[1] Support to define custom wait events for extensions
https://www.postgresql.org/message-id/flat/b9f5411acda0cf15c8fbb767702ff43e%40oss.nttdata.com

Regards,
--
Masahiro Ikeda
NTT DATA CORPORATIONFrom c6e60c66c4066b4a01981ffae5a168901e7283eb Mon Sep 17 00:00:00 2001
From: Masahiro Ikeda <masahiro.ikeda...@hco.ntt.co.jp>
Date: Thu, 20 Jul 2023 10:34:50 +0900
Subject: [PATCH] Support worker_spi to execute the function dynamically.

Currently, the database name to connect is initialized only
when process_shared_preload_libraries_in_progress is true.
It means that worker_spi_launch() fails if shared_preload_libraries
is empty because the database to connect is NULL.

The patch changes that the database name is always initilized
when called _PG_init(). We can call worker_spi_launch() and
launch SPI workers dynamically.
---
 src/test/modules/worker_spi/worker_spi.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/src/test/modules/worker_spi/worker_spi.c b/src/test/modules/worker_spi/worker_spi.c
index 7227cfaa45..ccc38a36d3 100644
--- a/src/test/modules/worker_spi/worker_spi.c
+++ b/src/test/modules/worker_spi/worker_spi.c
@@ -296,6 +296,15 @@ _PG_init(void)
 							NULL,
 							NULL);
 
+	DefineCustomStringVariable("worker_spi.database",
+							   "Database to connect to.",
+							   NULL,
+							   &worker_spi_database,
+							   "postgres",
+							   PGC_SIGHUP,
+							   0,
+							   NULL, NULL, NULL);
+
 	if (!process_shared_preload_libraries_in_progress)
 		return;
 
@@ -312,15 +321,6 @@ _PG_init(void)
 							NULL,
 							NULL);
 
-	DefineCustomStringVariable("worker_spi.database",
-							   "Database to connect to.",
-							   NULL,
-							   &worker_spi_database,
-							   "postgres",
-							   PGC_POSTMASTER,
-							   0,
-							   NULL, NULL, NULL);
-
 	MarkGUCPrefixReserved("worker_spi");
 
 	/* set up common data for all our workers */
-- 
2.25.1