slru-does-page-exist.patch

gistfile1.diff

diff --git a/src/backend/access/transam/multixact.c b/src/backend/access/transam/multixact.c
index 516a89f..ab85f6f 100644
--- a/src/backend/access/transam/multixact.c
+++ b/src/backend/access/transam/multixact.c
@@ -2734,7 +2734,7 @@ find_multixact_start(MultiXactId multi, MultiXactOffset *result)
 	pageno = MultiXactIdToOffsetPage(multi);
 	entryno = MultiXactIdToOffsetEntry(multi);
 
-	if (!SimpleLruDoesPhysicalPageExist(MultiXactOffsetCtl, pageno))
+	if (!SimpleLruDoesPageExist(MultiXactOffsetCtl, pageno))
 		return false;
 
 	/* lock is acquired by SimpleLruReadPage_ReadOnly */
diff --git a/src/backend/access/transam/slru.c b/src/backend/access/transam/slru.c
index 5fcea11..caf2a82 100644
--- a/src/backend/access/transam/slru.c
+++ b/src/backend/access/transam/slru.c
@@ -564,6 +564,41 @@ SimpleLruWritePage(SlruCtl ctl, int slotno)
 }
 
 /*
+ * Return whether the given page exists in a buffer or on disk.
+ */
+bool
+SimpleLruDoesPageExist(SlruCtl ctl, int pageno)
+{
+	return SimpleLruDoesBufferedPageExist(ctl, pageno) ||
+		SimpleLruDoesPhysicalPageExist(ctl, pageno);
+}
+
+/*
+ * Return whether the given page is currently buffered.
+ */
+bool
+SimpleLruDoesBufferedPageExist(SlruCtl ctl, int pageno)
+{
+	SlruShared	shared = ctl->shared;
+	bool   		result = false;
+	int			slotno;
+
+	LWLockAcquire(shared->ControlLock, LW_SHARED);
+	for (slotno = 0; slotno < shared->num_slots; slotno++)
+	{
+		if (shared->page_number[slotno] == pageno &&
+			shared->page_status[slotno] != SLRU_PAGE_EMPTY)
+		{
+			result = true;
+			break;
+		}
+	}
+	LWLockRelease(shared->ControlLock);
+
+	return result;
+}
+
+/*
  * Return whether the given page exists on disk.
  *
  * A false return means that either the file does not exist, or that it's not
diff --git a/src/include/access/slru.h b/src/include/access/slru.h
index 9c7f019..3907d7d 100644
--- a/src/include/access/slru.h
+++ b/src/include/access/slru.h
@@ -145,6 +145,8 @@ extern int SimpleLruReadPage_ReadOnly(SlruCtl ctl, int pageno,
 extern void SimpleLruWritePage(SlruCtl ctl, int slotno);
 extern void SimpleLruFlush(SlruCtl ctl, bool checkpoint);
 extern void SimpleLruTruncate(SlruCtl ctl, int cutoffPage);
+extern bool SimpleLruDoesPageExist(SlruCtl ctl, int pageno);
+extern bool SimpleLruDoesBufferedPageExist(SlruCtl ctl, int pageno);
 extern bool SimpleLruDoesPhysicalPageExist(SlruCtl ctl, int pageno);
 
 typedef bool (*SlruScanCallback) (SlruCtl ctl, char *filename, int segpage,