Add backendType to PGPROC, replacing isRegularBackend

We can immediately make use of it in pg_signal_backend(), which
previously fetched the process type from the backend status array with
pgstat_get_backend_type_by_proc_number(). That was correct but felt a
little questionable to me: backend status should be for observability
purposes only, not for permission checks.

Reviewed-by: Nathan Bossart <nathandbossart@gmail.com>
Reviewed-by: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Discussion: https://www.postgresql.org/message-id/b77e4962-a64a-43db-81a1-580444b3e8f5@iki.fi

diff --git a/src/backend/access/transam/twophase.c b/src/backend/access/transam/twophase.c
index 601ce3faa64b3475f892e21154ace11926140051..eabc4d48208f320eba4b9c08e817df0610233e5d 100644 (file)
--- a/src/backend/access/transam/twophase.c
+++ b/src/backend/access/transam/twophase.c
@@ -470,7 +470,7 @@ MarkAsPreparingGuts(GlobalTransaction gxact, FullTransactionId fxid,
        proc->databaseId = databaseid;
        proc->roleId = owner;
        proc->tempNamespaceId = InvalidOid;
-       proc->isRegularBackend = false;
+       proc->backendType = B_INVALID;
        proc->lwWaiting = LW_WS_NOT_WAITING;
        proc->lwWaitMode = 0;
        proc->waitLock = NULL;

diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c
index 748c06b51cba96dbed304c2a81f8e5832af5a800..301f54fb5a8a345429321e8c0a6c6c635942f07c 100644 (file)
--- a/src/backend/storage/ipc/procarray.c
+++ b/src/backend/storage/ipc/procarray.c
@@ -3589,7 +3589,7 @@ CountDBConnections(Oid databaseid)
 
                if (proc->pid == 0)
                        continue;                       /* do not count prepared xacts */
-               if (!proc->isRegularBackend)
+               if (proc->backendType != B_BACKEND)
                        continue;                       /* count only regular backend processes */
                if (!OidIsValid(databaseid) ||
                        proc->databaseId == databaseid)
@@ -3660,7 +3660,7 @@ CountUserBackends(Oid roleid)
 
                if (proc->pid == 0)
                        continue;                       /* do not count prepared xacts */
-               if (!proc->isRegularBackend)
+               if (proc->backendType != B_BACKEND)
                        continue;                       /* count only regular backend processes */
                if (proc->roleId == roleid)
                        count++;

diff --git a/src/backend/storage/ipc/signalfuncs.c b/src/backend/storage/ipc/signalfuncs.c
index 6f7759cd720cea1a17e6b809ae976c757d382b92..d48b4fe37997454ca3808b736c95972e4aeeabb5 100644 (file)
--- a/src/backend/storage/ipc/signalfuncs.c
+++ b/src/backend/storage/ipc/signalfuncs.c
@@ -87,10 +87,7 @@ pg_signal_backend(int pid, int sig)
         */
        if (!OidIsValid(proc->roleId) || superuser_arg(proc->roleId))
        {
-               ProcNumber      procNumber = GetNumberFromPGProc(proc);
-               BackendType backendType = pgstat_get_backend_type_by_proc_number(procNumber);
-
-               if (backendType == B_AUTOVAC_WORKER)
+               if (proc->backendType == B_AUTOVAC_WORKER)
                {
                        if (!has_privs_of_role(GetUserId(), ROLE_PG_SIGNAL_AUTOVACUUM_WORKER))
                                return SIGNAL_BACKEND_NOAUTOVAC;

diff --git a/src/backend/storage/lmgr/proc.c b/src/backend/storage/lmgr/proc.c
index fdeed0f3953480bd6da84f9c4d7341589e5e597d..c7a001b3b795d1ca33c894d80be98c640f180f0e 100644 (file)
--- a/src/backend/storage/lmgr/proc.c
+++ b/src/backend/storage/lmgr/proc.c
@@ -486,7 +486,7 @@ InitProcess(void)
        MyProc->databaseId = InvalidOid;
        MyProc->roleId = InvalidOid;
        MyProc->tempNamespaceId = InvalidOid;
-       MyProc->isRegularBackend = AmRegularBackendProcess();
+       MyProc->backendType = MyBackendType;
        MyProc->delayChkptFlags = 0;
        MyProc->statusFlags = 0;
        /* NB -- autovac launcher intentionally does not set IS_AUTOVACUUM */
@@ -684,7 +684,7 @@ InitAuxiliaryProcess(void)
        MyProc->databaseId = InvalidOid;
        MyProc->roleId = InvalidOid;
        MyProc->tempNamespaceId = InvalidOid;
-       MyProc->isRegularBackend = false;
+       MyProc->backendType = MyBackendType;
        MyProc->delayChkptFlags = 0;
        MyProc->statusFlags = 0;
        MyProc->lwWaiting = LW_WS_NOT_WAITING;

diff --git a/src/backend/utils/activity/backend_status.c b/src/backend/utils/activity/backend_status.c
index c84e65365807eb67f19c5fb7335ae1a92e0e8c8f..cd08712946911c88db5c70bf909c005f0696205f 100644 (file)
--- a/src/backend/utils/activity/backend_status.c
+++ b/src/backend/utils/activity/backend_status.c
@@ -1164,31 +1164,6 @@ pgstat_get_my_plan_id(void)
        return MyBEEntry->st_plan_id;
 }
 
-/* ----------
- * pgstat_get_backend_type_by_proc_number() -
- *
- *     Return the type of the backend with the specified ProcNumber.  This looks
- *     directly at the BackendStatusArray, so the return value may be out of date.
- *     The only current use of this function is in pg_signal_backend(), which is
- *     inherently racy, so we don't worry too much about this.
- *
- *     It is the caller's responsibility to use this wisely; at minimum, callers
- *     should ensure that procNumber is valid and perform the required permissions
- *     checks.
- * ----------
- */
-BackendType
-pgstat_get_backend_type_by_proc_number(ProcNumber procNumber)
-{
-       volatile PgBackendStatus *status = &BackendStatusArray[procNumber];
-
-       /*
-        * We bypass the changecount mechanism since fetching and storing an int
-        * is almost certainly atomic.
-        */
-       return status->st_backendType;
-}
-
 /* ----------
  * cmp_lbestatus
  *

diff --git a/src/include/storage/proc.h b/src/include/storage/proc.h
index 81f1960a635a28bc40aa3e0004675d1e0a5b5949..679f0624f928f888210ea5d31e56fb78000b1ca8 100644 (file)
--- a/src/include/storage/proc.h
+++ b/src/include/storage/proc.h
@@ -17,6 +17,7 @@
 #include "access/clog.h"
 #include "access/xlogdefs.h"
 #include "lib/ilist.h"
+#include "miscadmin.h"
 #include "storage/latch.h"
 #include "storage/lock.h"
 #include "storage/pg_sema.h"
@@ -166,7 +167,7 @@ typedef enum
  * but its myProcLocks[] lists are valid.
  *
  * We allow many fields of this struct to be accessed without locks, such as
- * delayChkptFlags and isRegularBackend. However, keep in mind that writing
+ * delayChkptFlags and backendType. However, keep in mind that writing
  * mirrored ones (see below) requires holding ProcArrayLock or XidGenLock in
  * at least shared mode, so that pgxactoff does not change concurrently.
  *
@@ -233,7 +234,7 @@ struct PGPROC
        Oid                     tempNamespaceId;        /* OID of temp schema this backend is
                                                                         * using */
 
-       bool            isRegularBackend;       /* true if it's a regular backend. */
+       BackendType backendType;        /* what kind of process is this? */
 
        /*
         * Info about LWLock the process is currently waiting for, if any.

diff --git a/src/include/utils/backend_status.h b/src/include/utils/backend_status.h
index 781e48c0c1069bd269efe4d2746ed43410340635..ddd06304e975ed70237ff86e04c7512ccc32c0ad 100644 (file)
--- a/src/include/utils/backend_status.h
+++ b/src/include/utils/backend_status.h
@@ -331,7 +331,6 @@ extern const char *pgstat_get_crashed_backend_activity(int pid, char *buffer,
                                                                                                           int buflen);
 extern int64 pgstat_get_my_query_id(void);
 extern int64 pgstat_get_my_plan_id(void);
-extern BackendType pgstat_get_backend_type_by_proc_number(ProcNumber procNumber);
 
 
 /* ----------