FWIW there's a stupid bug in 0002, which is fixed here. I'm writing a
simple test for it.
--
Álvaro Herrera 48°01'N 7°57'E — https://www.EnterpriseDB.com/
"Now I have my system running, not a byte was off the shelf;
It rarely breaks and when it does I fix the code myself.
It's stable, clean and elegant, and lightning fast as well,
And it doesn't cost a nickel, so Bill Gates can go to hell."
>From ecf613092a3cbc4c5112d30af7eea55b668decec Mon Sep 17 00:00:00 2001
From: Alvaro Herrera <alvhe...@alvh.no-ip.org>
Date: Mon, 4 Mar 2024 11:49:01 +0100
Subject: [PATCH v3] Rework redundant loop in subtrans.c
---
src/backend/access/transam/subtrans.c | 29 +++++++--------------------
1 file changed, 7 insertions(+), 22 deletions(-)
diff --git a/src/backend/access/transam/subtrans.c b/src/backend/access/transam/subtrans.c
index dc9566fb51..50bb1d8cfc 100644
--- a/src/backend/access/transam/subtrans.c
+++ b/src/backend/access/transam/subtrans.c
@@ -311,7 +311,7 @@ StartupSUBTRANS(TransactionId oldestActiveXID)
FullTransactionId nextXid;
int64 startPage;
int64 endPage;
- LWLock *prevlock;
+ LWLock *prevlock = NULL;
LWLock *lock;
/*
@@ -324,42 +324,27 @@ StartupSUBTRANS(TransactionId oldestActiveXID)
nextXid = TransamVariables->nextXid;
endPage = TransactionIdToPage(XidFromFullTransactionId(nextXid));
- prevlock = SimpleLruGetBankLock(SubTransCtl, startPage);
- LWLockAcquire(prevlock, LW_EXCLUSIVE);
- while (startPage != endPage)
+ for (;;)
{
lock = SimpleLruGetBankLock(SubTransCtl, startPage);
-
- /*
- * Check if we need to acquire the lock on the new bank then release
- * the lock on the old bank and acquire on the new bank.
- */
if (prevlock != lock)
{
- LWLockRelease(prevlock);
+ if (prevlock)
+ LWLockRelease(prevlock);
LWLockAcquire(lock, LW_EXCLUSIVE);
prevlock = lock;
}
(void) ZeroSUBTRANSPage(startPage);
+ if (startPage == endPage)
+ break;
+
startPage++;
/* must account for wraparound */
if (startPage > TransactionIdToPage(MaxTransactionId))
startPage = 0;
}
- lock = SimpleLruGetBankLock(SubTransCtl, startPage);
-
- /*
- * Check if we need to acquire the lock on the new bank then release the
- * lock on the old bank and acquire on the new bank.
- */
- if (prevlock != lock)
- {
- LWLockRelease(prevlock);
- LWLockAcquire(lock, LW_EXCLUSIVE);
- }
- (void) ZeroSUBTRANSPage(startPage);
LWLockRelease(lock);
}
--
2.39.2
