Used optimized linear search in more code paths

This commit updates two code paths to use pg_lfind32() introduced by
b6ef167 with TransactionId arrays:
- At the end of TransactionIdIsInProgress(), when checking for the case
of still running but overflowed subxids.
- XidIsConcurrent(), when checking for a serializable conflict.

These cases are less impactful than 37a6e5d, but a bit of
micro-benchmarking of this API shows that linear search speeds up by
~20% depending on the number of items involved (x86_64 and amd64 looked
at here).

Author: Nathan Bossart
Reviewed-by: Richard Guo, Michael Paquier
Discussion: https://postgr.es/m/20220901185153.GA783106@nathanxps13

diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c
index 382f4cfb736e4240d00919d97f065e4dae151465..207c4b27fdf8b9d34e64e704f4e8496d4ba70926 100644 (file)
--- a/src/backend/storage/ipc/procarray.c
+++ b/src/backend/storage/ipc/procarray.c
@@ -58,6 +58,7 @@
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
 #include "pgstat.h"
+#include "port/pg_lfind.h"
 #include "storage/proc.h"
 #include "storage/procarray.h"
 #include "storage/spin.h"
@@ -1586,14 +1587,9 @@ TransactionIdIsInProgress(TransactionId xid)
     */
    topxid = SubTransGetTopmostTransaction(xid);
    Assert(TransactionIdIsValid(topxid));
-   if (!TransactionIdEquals(topxid, xid))
-   {
-       for (int i = 0; i < nxids; i++)
-       {
-           if (TransactionIdEquals(xids[i], topxid))
-               return true;
-       }
-   }
+   if (!TransactionIdEquals(topxid, xid) &&
+       pg_lfind32(topxid, xids, nxids))
+       return true;
 
    cachedXidIsNotInProgress = xid;
    return false;

diff --git a/src/backend/storage/lmgr/predicate.c b/src/backend/storage/lmgr/predicate.c
index 5f2a4805d82d07ebe1e36686f81265652fbc74fb..e8120174d61b22e47af0202ce848bfca3686de04 100644 (file)
--- a/src/backend/storage/lmgr/predicate.c
+++ b/src/backend/storage/lmgr/predicate.c
@@ -202,6 +202,7 @@
 #include "access/xlog.h"
 #include "miscadmin.h"
 #include "pgstat.h"
+#include "port/pg_lfind.h"
 #include "storage/bufmgr.h"
 #include "storage/predicate.h"
 #include "storage/predicate_internals.h"
@@ -4065,7 +4066,6 @@ static bool
 XidIsConcurrent(TransactionId xid)
 {
    Snapshot    snap;
-   uint32      i;
 
    Assert(TransactionIdIsValid(xid));
    Assert(!TransactionIdEquals(xid, GetTopTransactionIdIfAny()));
@@ -4078,13 +4078,7 @@ XidIsConcurrent(TransactionId xid)
    if (TransactionIdFollowsOrEquals(xid, snap->xmax))
        return true;
 
-   for (i = 0; i < snap->xcnt; i++)
-   {
-       if (xid == snap->xip[i])
-           return true;
-   }
-
-   return false;
+   return pg_lfind32(xid, snap->xip, snap->xcnt);
 }
 
 bool