Make sure MaxBackends is always set

Auxiliary and bootstrap processes weren't getting it, causing initdb to
fail completely.

1 files changed, 22 insertions, 0 deletions

diff --git a/src/backend/utils/init/postinit.c b/src/backend/utils/init/postinit.c
index 0fbf65f7340..3948eac039b 100644
--- a/src/backend/utils/init/postinit.c
+++ b/src/backend/utils/init/postinit.c
@@ -421,6 +421,26 @@ pg_split_opts(char **argv, int *argcp, char *optstr)
 	}
 }
 
+/*
+ * Initialize MaxBackends value from config options.
+ *
+ * This must be called after modules have had the chance to register background
+ * workers in shared_preload_libraries, and before shared memory size is
+ * determined.
+ */
+void
+InitializeMaxBackends(void)
+{
+	Assert(MaxBackends == 0);
+
+	/* the extra unit accounts for the autovacuum launcher */
+	MaxBackends = MaxConnections + autovacuum_max_workers + 1 +
+		GetNumShmemAttachedBgworkers();
+
+	/* internal error because the values were all checked previously */
+	if (MaxBackends > MAX_BACKENDS)
+		elog(ERROR, "too many backends configured");
+}
 
 /*
  * Early initialization of a backend (either standalone or under postmaster).
@@ -433,6 +453,8 @@ pg_split_opts(char **argv, int *argcp, char *optstr)
 void
 BaseInit(void)
 {
+	InitializeMaxBackends();
+
 	/*
 	 * Attach to shared memory and semaphores, and initialize our
 	 * input/output/debugging file descriptors.