Merge branch 'apache:main' into main

Author: reshke

doc/src/sgml/func.sgml

@@ -15446,6 +15446,10 @@ table2-mapping
        <para>
         <literal>json_array_length('[1,2,3,{"f1":1,"f2":[5,6]},4]')</literal>
         <returnvalue>5</returnvalue>
+       </para>
+       <para>
+        <literal>jsonb_array_length('[]')</literal>
+        <returnvalue>0</returnvalue>
        </para></entry>
       </row>
 
@@ -17887,10 +17891,19 @@ SELECT NULLIF(value, '(none)') ...
        </para>
        <para>
         Returns the length of the requested array dimension.
+        (Produces NULL instead of 0 for empty or missing array dimensions.)
        </para>
        <para>
         <literal>array_length(array[1,2,3], 1)</literal>
         <returnvalue>3</returnvalue>
+       </para>
+       <para>
+        <literal>array_length(array[]::int[], 1)</literal>
+        <returnvalue>NULL</returnvalue>
+       </para>
+       <para>
+        <literal>array_length(array['text'], 2)</literal>
+        <returnvalue>NULL</returnvalue>
        </para></entry>
       </row>
 

doc/src/sgml/json.sgml

@@ -701,10 +701,10 @@ UPDATE table_name SET jsonb_field[2] = '2';
    assigned value can be placed.
 
 <programlisting>
--- Where jsonb_field was {}, it is now {'a': [{'b': 1}]}
+-- Where jsonb_field was {}, it is now {"a": [{"b": 1}]}
 UPDATE table_name SET jsonb_field['a'][0]['b'] = '1';
 
--- Where jsonb_field was [], it is now [null, {'a': 1}]
+-- Where jsonb_field was [], it is now [null, {"a": 1}]
 UPDATE table_name SET jsonb_field[1]['a'] = '1';
 </programlisting>
 

src/backend/access/transam/transam.c

@@ -249,10 +249,15 @@ TransactionIdDidAbortForReader(TransactionId transactionId)
  *
  * This does NOT look into pg_xact but merely probes our local cache
  * (and so it's not named TransactionIdDidComplete, which would be the
- * appropriate name for a function that worked that way).  The intended
- * use is just to short-circuit TransactionIdIsInProgress calls when doing
- * repeated heapam_visibility.c checks for the same XID.  If this isn't
- * extremely fast then it will be counterproductive.
+ * appropriate name for a function that worked that way).
+ *
+ * NB: This is unused, and will be removed in v15. This was used to
+ * short-circuit TransactionIdIsInProgress, but that was wrong for a
+ * transaction that was known to be marked as committed in CLOG but not
+ * yet removed from the proc array. This is kept in backbranches just in
+ * case it is still used by extensions.  However, extensions doing
+ * something similar to tuple visibility checks should also be careful to
+ * check the proc array first!
  *
  * Note:
  *		Assumes transaction identifier is valid.

src/backend/storage/ipc/latch.c

@@ -72,7 +72,7 @@
 #if defined(WAIT_USE_EPOLL) || defined(WAIT_USE_POLL) || \
 	defined(WAIT_USE_KQUEUE) || defined(WAIT_USE_WIN32)
 /* don't overwrite manual choice */
-#elif defined(HAVE_SYS_EPOLL_H) && defined(HAVE_SYS_SIGNALFD_H)
+#elif defined(HAVE_SYS_EPOLL_H)
 #define WAIT_USE_EPOLL
 #elif defined(HAVE_KQUEUE)
 #define WAIT_USE_KQUEUE
@@ -84,6 +84,22 @@
 #error "no wait set implementation available"
 #endif
 
+/*
+ * By default, we use a self-pipe with poll() and a signalfd with epoll(), if
+ * available.  We avoid signalfd on illumos for now based on problem reports.
+ * For testing the choice can also be manually specified.
+ */
+#if defined(WAIT_USE_POLL) || defined(WAIT_USE_EPOLL)
+#if defined(WAIT_USE_SELF_PIPE) || defined(WAIT_USE_SIGNALFD)
+/* don't overwrite manual choice */
+#elif defined(WAIT_USE_EPOLL) && defined(HAVE_SYS_SIGNALFD_H) && \
+	!defined(__illumos__)
+#define WAIT_USE_SIGNALFD
+#else
+#define WAIT_USE_SELF_PIPE
+#endif
+#endif
+
 /* typedef in latch.h */
 struct WaitEventSet
 {
@@ -146,12 +162,12 @@ static WaitEventSet *LatchWaitSet;
 static volatile sig_atomic_t waiting = false;
 #endif
 
-#ifdef WAIT_USE_EPOLL
+#ifdef WAIT_USE_SIGNALFD
 /* On Linux, we'll receive SIGURG via a signalfd file descriptor. */
 static int	signal_fd = -1;
 #endif
 
-#if defined(WAIT_USE_POLL)
+#ifdef WAIT_USE_SELF_PIPE
 /* Read and write ends of the self-pipe */
 static int	selfpipe_readfd = -1;
 static int	selfpipe_writefd = -1;
@@ -164,7 +180,7 @@ static void latch_sigurg_handler(SIGNAL_ARGS);
 static void sendSelfPipeByte(void);
 #endif
 
-#if defined(WAIT_USE_POLL) || defined(WAIT_USE_EPOLL)
+#if defined(WAIT_USE_SELF_PIPE) || defined(WAIT_USE_SIGNALFD)
 static void drain(void);
 #endif
 
@@ -190,7 +206,7 @@ static inline int WaitEventSetWaitBlock(WaitEventSet *set, int cur_timeout,
 void
 InitializeLatchSupport(void)
 {
-#if defined(WAIT_USE_POLL)
+#if defined(WAIT_USE_SELF_PIPE)
 	int			pipefd[2];
 
 	if (IsUnderPostmaster)
@@ -264,7 +280,7 @@ InitializeLatchSupport(void)
 	pqsignal(SIGURG, latch_sigurg_handler);
 #endif
 
-#ifdef WAIT_USE_EPOLL
+#ifdef WAIT_USE_SIGNALFD
 	sigset_t	signalfd_mask;
 
 	/* Block SIGURG, because we'll receive it through a signalfd. */
@@ -316,15 +332,15 @@ ShutdownLatchSupport(void)
 		LatchWaitSet = NULL;
 	}
 
-#if defined(WAIT_USE_POLL)
+#if defined(WAIT_USE_SELF_PIPE)
 	close(selfpipe_readfd);
 	close(selfpipe_writefd);
 	selfpipe_readfd = -1;
 	selfpipe_writefd = -1;
 	selfpipe_owner_pid = InvalidPid;
 #endif
 
-#if defined(WAIT_USE_EPOLL)
+#if defined(WAIT_USE_SIGNALFD)
 	close(signal_fd);
 	signal_fd = -1;
 #endif
@@ -341,9 +357,12 @@ InitLatch(Latch *latch)
 	latch->owner_pid = MyProcPid;
 	latch->is_shared = false;
 
-#if defined(WAIT_USE_POLL)
+#if defined(WAIT_USE_SELF_PIPE)
 	/* Assert InitializeLatchSupport has been called in this process */
 	Assert(selfpipe_readfd >= 0 && selfpipe_owner_pid == MyProcPid);
+#elif defined(WAIT_USE_SIGNALFD)
+	/* Assert InitializeLatchSupport has been called in this process */
+	Assert(signal_fd >= 0);
 #elif defined(WAIT_USE_WIN32)
 	latch->event = CreateEvent(NULL, TRUE, FALSE, NULL);
 	if (latch->event == NULL)
@@ -405,9 +424,12 @@ OwnLatch(Latch *latch)
 	/* Sanity checks */
 	Assert(latch->is_shared);
 
-#if defined(WAIT_USE_POLL)
+#if defined(WAIT_USE_SELF_PIPE)
 	/* Assert InitializeLatchSupport has been called in this process */
 	Assert(selfpipe_readfd >= 0 && selfpipe_owner_pid == MyProcPid);
+#elif defined(WAIT_USE_SIGNALFD)
+	/* Assert InitializeLatchSupport has been called in this process */
+	Assert(signal_fd >= 0);
 #endif
 
 	if (latch->owner_pid != 0)
@@ -618,7 +640,7 @@ SetLatch(Latch *latch)
 		return;
 	else if (owner_pid == MyProcPid)
 	{
-#if defined(WAIT_USE_POLL)
+#if defined(WAIT_USE_SELF_PIPE)
 		if (waiting)
 			sendSelfPipeByte();
 #else
@@ -983,9 +1005,9 @@ AddWaitEventToSet(WaitEventSet *set, uint32 events, pgsocket fd, Latch *latch,
 	{
 		set->latch = latch;
 		set->latch_pos = event->pos;
-#if defined(WAIT_USE_POLL)
+#if defined(WAIT_USE_SELF_PIPE)
 		event->fd = selfpipe_readfd;
-#elif defined(WAIT_USE_EPOLL)
+#elif defined(WAIT_USE_SIGNALFD)
 		event->fd = signal_fd;
 #else
 		event->fd = PGINVALID_SOCKET;
@@ -2102,7 +2124,7 @@ GetNumRegisteredWaitEvents(WaitEventSet *set)
 	return set->nevents;
 }
 
-#if defined(WAIT_USE_POLL)
+#if defined(WAIT_USE_SELF_PIPE)
 
 /*
  * SetLatch uses SIGURG to wake up the process waiting on the latch.
@@ -2153,7 +2175,7 @@ sendSelfPipeByte(void)
 
 #endif
 
-#if defined(WAIT_USE_POLL) || defined(WAIT_USE_EPOLL)
+#if defined(WAIT_USE_SELF_PIPE) || defined(WAIT_USE_SIGNALFD)
 
 /*
  * Read all available data from self-pipe or signalfd.
@@ -2169,7 +2191,7 @@ drain(void)
 	int			rc;
 	int			fd;
 
-#ifdef WAIT_USE_POLL
+#ifdef WAIT_USE_SELF_PIPE
 	fd = selfpipe_readfd;
 #else
 	fd = signal_fd;
@@ -2187,7 +2209,7 @@ drain(void)
 			else
 			{
 				waiting = false;
-#ifdef WAIT_USE_POLL
+#ifdef WAIT_USE_SELF_PIPE
 				elog(ERROR, "read() on self-pipe failed: %m");
 #else
 				elog(ERROR, "read() on signalfd failed: %m");
@@ -2197,7 +2219,7 @@ drain(void)
 		else if (rc == 0)
 		{
 			waiting = false;
-#ifdef WAIT_USE_POLL
+#ifdef WAIT_USE_SELF_PIPE
 			elog(ERROR, "unexpected EOF on self-pipe");
 #else
 			elog(ERROR, "unexpected EOF on signalfd");

src/backend/storage/ipc/procarray.c

@@ -277,6 +277,11 @@ static ProcArrayStruct *procArray;
 static PGPROC *allProcs;
 static TMGXACT *allTmGxact;
 
+/*
+ * Cache to reduce overhead of repeated calls to TransactionIdIsInProgress()
+ */
+static TransactionId cachedXidIsNotInProgress = InvalidTransactionId;
+
 /*
  * Bookkeeping for tracking emulated transactions in recovery
  */
@@ -1486,7 +1491,7 @@ TransactionIdIsInProgress(TransactionId xid)
 	 * already known to be completed, we can fall out without any access to
 	 * shared memory.
 	 */
-	if (TransactionIdIsKnownCompleted(xid))
+	if (TransactionIdEquals(cachedXidIsNotInProgress, xid))
 	{
 		xc_by_known_xact_inc();
 		return false;
@@ -1644,6 +1649,7 @@ TransactionIdIsInProgress(TransactionId xid)
 	if (nxids == 0)
 	{
 		xc_no_overflow_inc();
+		cachedXidIsNotInProgress = xid;
 		return false;
 	}
 
@@ -1658,7 +1664,10 @@ TransactionIdIsInProgress(TransactionId xid)
 	xc_slow_answer_inc();
 
 	if (TransactionIdDidAbort(xid))
+	{
+		cachedXidIsNotInProgress = xid;
 		return false;
+	}
 
 	/*
 	 * It isn't aborted, so check whether the transaction tree it belongs to
@@ -1676,6 +1685,7 @@ TransactionIdIsInProgress(TransactionId xid)
 		}
 	}
 
+	cachedXidIsNotInProgress = xid;
 	return false;
 }
 

src/backend/storage/ipc/signalfuncs.c

@@ -52,7 +52,6 @@ static int
 pg_signal_backend(int pid, int sig, char *msg)
 {
 	PGPROC	   *proc = BackendPidGetProc(pid);
-	LocalPgBackendStatus *local_beentry;
 
 	/*
 	 * BackendPidGetProc returns NULL if the pid isn't valid; but by the time
@@ -73,34 +72,14 @@ pg_signal_backend(int pid, int sig, char *msg)
 		return SIGNAL_BACKEND_ERROR;
 	}
 
-	local_beentry = pgstat_fetch_stat_local_beentry_by_pid(pid);
-
-	/* Only allow superusers to signal superuser-owned backends. */
-	if (superuser_arg(proc->roleId) && !superuser())
-	{
-		Oid role;
-		char * appname;
-
-		if (local_beentry == NULL) {
-			return SIGNAL_BACKEND_NOSUPERUSER;
-		}
-
-		role = get_role_oid("mdb_admin", true /*if nodoby created mdb_admin role in this database*/);
-		appname = local_beentry->backendStatus.st_appname;
-
-		// only allow mdb_admin to kill su queries
-		if (!is_member_of_role(GetUserId(), role)) {
-			return SIGNAL_BACKEND_NOSUPERUSER;
-		}
-
-		if (local_beentry->backendStatus.st_backendType == B_AUTOVAC_WORKER) {
-			// ok
-		} else if (appname != NULL && strcmp(appname, "MDB") == 0) {
-			// ok
-		} else {
-			return SIGNAL_BACKEND_NOSUPERUSER;
-		}
-	}
+	/*
+	 * Only allow superusers to signal superuser-owned backends.  Any process
+	 * not advertising a role might have the importance of a superuser-owned
+	 * backend, so treat it that way.
+	 */
+	if ((!OidIsValid(proc->roleId) || superuser_arg(proc->roleId)) &&
+		!superuser())
+		return SIGNAL_BACKEND_NOSUPERUSER;
 
 	/* Users can signal backends they have role membership in. */
 	if (!has_privs_of_role(GetUserId(), proc->roleId) &&

src/backend/utils/adt/xid8funcs.c

@@ -36,6 +36,7 @@
 #include "miscadmin.h"
 #include "postmaster/postmaster.h"
 #include "storage/lwlock.h"
+#include "storage/procarray.h"
 #include "utils/builtins.h"
 #include "utils/memutils.h"
 #include "utils/snapmgr.h"
@@ -810,29 +811,22 @@ pg_xact_status(PG_FUNCTION_ARGS)
 	{
 		Assert(TransactionIdIsValid(xid));
 
-		if (TransactionIdIsCurrentTransactionId(xid))
+		/*
+		 * Like when doing visiblity checks on a row, check whether the
+		 * transaction is still in progress before looking into the CLOG.
+		 * Otherwise we would incorrectly return "committed" for a transaction
+		 * that is committing and has already updated the CLOG, but hasn't
+		 * removed its XID from the proc array yet. (See comment on that race
+		 * condition at the top of heapam_visibility.c)
+		 */
+		if (TransactionIdIsInProgress(xid))
 			status = "in progress";
 		else if (TransactionIdDidCommit(xid))
 			status = "committed";
-		else if (TransactionIdDidAbort(xid))
-			status = "aborted";
 		else
 		{
-			/*
-			 * The xact is not marked as either committed or aborted in clog.
-			 *
-			 * It could be a transaction that ended without updating clog or
-			 * writing an abort record due to a crash. We can safely assume
-			 * it's aborted if it isn't committed and is older than our
-			 * snapshot xmin.
-			 *
-			 * Otherwise it must be in-progress (or have been at the time we
-			 * checked commit/abort status).
-			 */
-			if (TransactionIdPrecedes(xid, GetActiveSnapshot()->xmin))
-				status = "aborted";
-			else
-				status = "in progress";
+			/* it must have aborted or crashed */
+			status = "aborted";
 		}
 	}
 	else