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Use callbacks in SlruScanDirectory for the actual action

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Previously, the code assumed that the only possible action to take was
to delete files behind a certain cutoff point.  The async notify code
was already a crock: it used a different "pagePrecedes" function for
truncation than for regular operation.  By allowing it to pass a
callback to SlruScanDirectory it can do cleanly exactly what it needs to
do.

The clog.c code also had its own use for SlruScanDirectory, which is
made a bit simpler with this.
This commit is contained in:
Alvaro Herrera
2011-09-28 11:32:38 -03:00
parent 1a00c0ef53
commit 09e196e453
4 changed files with 95 additions and 60 deletions
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36
src/backend/commands/async.c
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@ -194,7 +194,7 @@ typedef struct QueuePosition
/* choose logically smaller QueuePosition */
#define QUEUE_POS_MIN(x,y) \
(asyncQueuePagePrecedesLogically((x).page, (y).page) ? (x) : \
(asyncQueuePagePrecedes((x).page, (y).page) ? (x) : \
(x).page != (y).page ? (y) : \
(x).offset < (y).offset ? (x) : (y))
@ -360,8 +360,7 @@ static bool backendHasExecutedInitialListen = false;
bool Trace_notify = false;
/* local function prototypes */
static bool asyncQueuePagePrecedesPhysically(int p, int q);
static bool asyncQueuePagePrecedesLogically(int p, int q);
static bool asyncQueuePagePrecedes(int p, int q);
static void queue_listen(ListenActionKind action, const char *channel);
static void Async_UnlistenOnExit(int code, Datum arg);
static void Exec_ListenPreCommit(void);
@ -388,25 +387,11 @@ static void NotifyMyFrontEnd(const char *channel,
static bool AsyncExistsPendingNotify(const char *channel, const char *payload);
static void ClearPendingActionsAndNotifies(void);
/*
* We will work on the page range of 0..QUEUE_MAX_PAGE.
*
* asyncQueuePagePrecedesPhysically just checks numerically without any magic
* if one page precedes another one. This is wrong for normal operation but
* is helpful when clearing pg_notify/ during startup.
*
* asyncQueuePagePrecedesLogically compares using wraparound logic, as is
* required by slru.c.
*/
static bool
asyncQueuePagePrecedesPhysically(int p, int q)
{
return p < q;
}
static bool
asyncQueuePagePrecedesLogically(int p, int q)
asyncQueuePagePrecedes(int p, int q)
{
int diff;
@ -484,7 +469,7 @@ AsyncShmemInit(void)
/*
* Set up SLRU management of the pg_notify data.
*/
AsyncCtl->PagePrecedes = asyncQueuePagePrecedesLogically;
AsyncCtl->PagePrecedes = asyncQueuePagePrecedes;
SimpleLruInit(AsyncCtl, "Async Ctl", NUM_ASYNC_BUFFERS, 0,
AsyncCtlLock, "pg_notify");
/* Override default assumption that writes should be fsync'd */
@ -494,15 +479,8 @@ AsyncShmemInit(void)
{
/*
* During start or reboot, clean out the pg_notify directory.
*
* Since we want to remove every file, we temporarily use
* asyncQueuePagePrecedesPhysically() and pass INT_MAX as the
* comparison value; every file in the directory should therefore
* appear to be less than that.
*/
AsyncCtl->PagePrecedes = asyncQueuePagePrecedesPhysically;
(void) SlruScanDirectory(AsyncCtl, INT_MAX, true);
AsyncCtl->PagePrecedes = asyncQueuePagePrecedesLogically;
(void) SlruScanDirectory(AsyncCtl, SlruScanDirCbDeleteAll, NULL);
/* Now initialize page zero to empty */
LWLockAcquire(AsyncCtlLock, LW_EXCLUSIVE);
@ -1223,7 +1201,7 @@ asyncQueueIsFull(void)
nexthead = 0; /* wrap around */
boundary = QUEUE_POS_PAGE(QUEUE_TAIL);
boundary -= boundary % SLRU_PAGES_PER_SEGMENT;
return asyncQueuePagePrecedesLogically(nexthead, boundary);
return asyncQueuePagePrecedes(nexthead, boundary);
}
/*
@ -2074,7 +2052,7 @@ asyncQueueAdvanceTail(void)
*/
newtailpage = QUEUE_POS_PAGE(min);
boundary = newtailpage - (newtailpage % SLRU_PAGES_PER_SEGMENT);
if (asyncQueuePagePrecedesLogically(oldtailpage, boundary))
if (asyncQueuePagePrecedes(oldtailpage, boundary))
{
/*
* SimpleLruTruncate() will ask for AsyncCtlLock but will also release