diff options
Diffstat (limited to 'src/backend/access/transam/clog.c')
| -rw-r--r-- | src/backend/access/transam/clog.c | 140 |
1 files changed, 75 insertions, 65 deletions
diff --git a/src/backend/access/transam/clog.c b/src/backend/access/transam/clog.c index cd83da93ea6..1436b32aa16 100644 --- a/src/backend/access/transam/clog.c +++ b/src/backend/access/transam/clog.c @@ -13,7 +13,7 @@ * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * - * $Header: /cvsroot/pgsql/src/backend/access/transam/clog.c,v 1.4 2001/09/29 04:02:21 tgl Exp $ + * $Header: /cvsroot/pgsql/src/backend/access/transam/clog.c,v 1.5 2001/10/25 05:49:22 momjian Exp $ * *------------------------------------------------------------------------- */ @@ -33,7 +33,7 @@ /* * Defines for CLOG page and segment sizes. A page is the same BLCKSZ - * as is used everywhere else in Postgres. The CLOG segment size can be + * as is used everywhere else in Postgres. The CLOG segment size can be * chosen somewhat arbitrarily; we make it 1 million transactions by default, * or 256Kb. * @@ -48,15 +48,15 @@ /* We need two bits per xact, so four xacts fit in a byte */ #define CLOG_BITS_PER_XACT 2 -#define CLOG_XACTS_PER_BYTE 4 -#define CLOG_XACTS_PER_PAGE (CLOG_BLCKSZ * CLOG_XACTS_PER_BYTE) +#define CLOG_XACTS_PER_BYTE 4 +#define CLOG_XACTS_PER_PAGE (CLOG_BLCKSZ * CLOG_XACTS_PER_BYTE) #define CLOG_XACT_BITMASK ((1 << CLOG_BITS_PER_XACT) - 1) #define CLOG_XACTS_PER_SEGMENT 0x100000 #define CLOG_PAGES_PER_SEGMENT (CLOG_XACTS_PER_SEGMENT / CLOG_XACTS_PER_PAGE) #define TransactionIdToPage(xid) ((xid) / (TransactionId) CLOG_XACTS_PER_PAGE) -#define TransactionIdToPgIndex(xid) ((xid) % (TransactionId) CLOG_XACTS_PER_PAGE) +#define TransactionIdToPgIndex(xid) ((xid) % (TransactionId) CLOG_XACTS_PER_PAGE) #define TransactionIdToByte(xid) (TransactionIdToPgIndex(xid) / CLOG_XACTS_PER_BYTE) #define TransactionIdToBIndex(xid) ((xid) % (TransactionId) CLOG_XACTS_PER_BYTE) @@ -101,15 +101,15 @@ * the control lock. * * As with the regular buffer manager, it is possible for another process - * to re-dirty a page that is currently being written out. This is handled + * to re-dirty a page that is currently being written out. This is handled * by setting the page's state from WRITE_IN_PROGRESS to DIRTY. The writing * process must notice this and not mark the page CLEAN when it's done. * * XLOG interactions: this module generates an XLOG record whenever a new - * CLOG page is initialized to zeroes. Other writes of CLOG come from + * CLOG page is initialized to zeroes. Other writes of CLOG come from * recording of transaction commit or abort in xact.c, which generates its * own XLOG records for these events and will re-perform the status update - * on redo; so we need make no additional XLOG entry here. Also, the XLOG + * on redo; so we need make no additional XLOG entry here. Also, the XLOG * is guaranteed flushed through the XLOG commit record before we are called * to log a commit, so the WAL rule "write xlog before data" is satisfied * automatically for commits, and we don't really care for aborts. Therefore, @@ -120,11 +120,13 @@ typedef enum { - CLOG_PAGE_EMPTY, /* CLOG buffer is not in use */ - CLOG_PAGE_READ_IN_PROGRESS, /* CLOG page is being read in */ - CLOG_PAGE_CLEAN, /* CLOG page is valid and not dirty */ - CLOG_PAGE_DIRTY, /* CLOG page is valid but needs write */ - CLOG_PAGE_WRITE_IN_PROGRESS /* CLOG page is being written out in */ + CLOG_PAGE_EMPTY,/* CLOG buffer is not in use */ + CLOG_PAGE_READ_IN_PROGRESS, /* CLOG page is being read + * in */ + CLOG_PAGE_CLEAN,/* CLOG page is valid and not dirty */ + CLOG_PAGE_DIRTY,/* CLOG page is valid but needs write */ + CLOG_PAGE_WRITE_IN_PROGRESS /* CLOG page is being + * written out in */ } ClogPageStatus; /* @@ -134,14 +136,15 @@ typedef struct ClogCtlData { /* * Info for each buffer slot. Page number is undefined when status is - * EMPTY. lru_count is essentially the number of operations since last - * use of this page; the page with highest lru_count is the best candidate - * to replace. + * EMPTY. lru_count is essentially the number of operations since + * last use of this page; the page with highest lru_count is the best + * candidate to replace. */ char *page_buffer[NUM_CLOG_BUFFERS]; - ClogPageStatus page_status[NUM_CLOG_BUFFERS]; + ClogPageStatus page_status[NUM_CLOG_BUFFERS]; int page_number[NUM_CLOG_BUFFERS]; - unsigned int page_lru_count[NUM_CLOG_BUFFERS]; + unsigned int page_lru_count[NUM_CLOG_BUFFERS]; + /* * latest_page_number is the page number of the current end of the * CLOG; this is not critical data, since we use it only to avoid @@ -157,7 +160,7 @@ static ClogCtlData *ClogCtl = NULL; * The value is automatically inherited by backends via fork, and * doesn't need to be in shared memory. */ -static LWLockId ClogBufferLocks[NUM_CLOG_BUFFERS]; /* Per-buffer I/O locks */ +static LWLockId ClogBufferLocks[NUM_CLOG_BUFFERS]; /* Per-buffer I/O locks */ /* * ClogDir is set during CLOGShmemInit and does not change thereafter. @@ -166,7 +169,7 @@ static LWLockId ClogBufferLocks[NUM_CLOG_BUFFERS]; /* Per-buffer I/O locks */ */ static char ClogDir[MAXPGPATH]; -#define ClogFileName(path, seg) \ +#define ClogFileName(path, seg) \ snprintf(path, MAXPGPATH, "%s/%04X", ClogDir, seg) /* @@ -430,7 +433,7 @@ ReadCLOGPage(int pageno) LWLockAcquire(CLogControlLock, LW_EXCLUSIVE); Assert(ClogCtl->page_number[slotno] == pageno && - ClogCtl->page_status[slotno] == CLOG_PAGE_READ_IN_PROGRESS); + ClogCtl->page_status[slotno] == CLOG_PAGE_READ_IN_PROGRESS); ClogCtl->page_status[slotno] = CLOG_PAGE_CLEAN; @@ -447,7 +450,7 @@ ReadCLOGPage(int pageno) * * NOTE: only one write attempt is made here. Hence, it is possible that * the page is still dirty at exit (if someone else re-dirtied it during - * the write). However, we *do* attempt a fresh write even if the page + * the write). However, we *do* attempt a fresh write even if the page * is already being written; this is for checkpoints. * * Control lock must be held at entry, and will be held at exit. @@ -455,7 +458,7 @@ ReadCLOGPage(int pageno) static void WriteCLOGPage(int slotno) { - int pageno; + int pageno; /* Do nothing if page does not need writing */ if (ClogCtl->page_status[slotno] != CLOG_PAGE_DIRTY && @@ -489,11 +492,12 @@ WriteCLOGPage(int slotno) * update on this page will mark it dirty again. NB: we are assuming * that read/write of the page status field is atomic, since we change * the state while not holding control lock. However, we cannot set - * this state any sooner, or we'd possibly fool a previous writer - * into thinking he's successfully dumped the page when he hasn't. - * (Scenario: other writer starts, page is redirtied, we come along and - * set WRITE_IN_PROGRESS again, other writer completes and sets CLEAN - * because redirty info has been lost, then we think it's clean too.) + * this state any sooner, or we'd possibly fool a previous writer into + * thinking he's successfully dumped the page when he hasn't. + * (Scenario: other writer starts, page is redirtied, we come along + * and set WRITE_IN_PROGRESS again, other writer completes and sets + * CLEAN because redirty info has been lost, then we think it's clean + * too.) */ ClogCtl->page_status[slotno] = CLOG_PAGE_WRITE_IN_PROGRESS; @@ -523,7 +527,7 @@ WriteCLOGPage(int slotno) static void CLOGPhysicalReadPage(int pageno, int slotno) { - int segno = pageno / CLOG_PAGES_PER_SEGMENT; + int segno = pageno / CLOG_PAGES_PER_SEGMENT; int rpageno = pageno % CLOG_PAGES_PER_SEGMENT; int offset = rpageno * CLOG_BLCKSZ; char path[MAXPGPATH]; @@ -533,9 +537,9 @@ CLOGPhysicalReadPage(int pageno, int slotno) /* * In a crash-and-restart situation, it's possible for us to receive - * commands to set the commit status of transactions whose bits are - * in already-truncated segments of the commit log (see notes in - * CLOGPhysicalWritePage). Hence, if we are InRecovery, allow the + * commands to set the commit status of transactions whose bits are in + * already-truncated segments of the commit log (see notes in + * CLOGPhysicalWritePage). Hence, if we are InRecovery, allow the * case where the file doesn't exist, and return zeroes instead. */ fd = BasicOpenFile(path, O_RDWR | PG_BINARY, S_IRUSR | S_IWUSR); @@ -569,7 +573,7 @@ CLOGPhysicalReadPage(int pageno, int slotno) static void CLOGPhysicalWritePage(int pageno, int slotno) { - int segno = pageno / CLOG_PAGES_PER_SEGMENT; + int segno = pageno / CLOG_PAGES_PER_SEGMENT; int rpageno = pageno % CLOG_PAGES_PER_SEGMENT; int offset = rpageno * CLOG_BLCKSZ; char path[MAXPGPATH]; @@ -578,16 +582,17 @@ CLOGPhysicalWritePage(int pageno, int slotno) ClogFileName(path, segno); /* - * If the file doesn't already exist, we should create it. It is possible - * for this to need to happen when writing a page that's not first in - * its segment; we assume the OS can cope with that. (Note: it might seem - * that it'd be okay to create files only when ZeroCLOGPage is called for - * the first page of a segment. However, if after a crash and restart - * the REDO logic elects to replay the log from a checkpoint before the - * latest one, then it's possible that we will get commands to set - * transaction status of transactions that have already been truncated - * from the commit log. Easiest way to deal with that is to accept - * references to nonexistent files here and in CLOGPhysicalReadPage.) + * If the file doesn't already exist, we should create it. It is + * possible for this to need to happen when writing a page that's not + * first in its segment; we assume the OS can cope with that. (Note: + * it might seem that it'd be okay to create files only when + * ZeroCLOGPage is called for the first page of a segment. However, + * if after a crash and restart the REDO logic elects to replay the + * log from a checkpoint before the latest one, then it's possible + * that we will get commands to set transaction status of transactions + * that have already been truncated from the commit log. Easiest way + * to deal with that is to accept references to nonexistent files here + * and in CLOGPhysicalReadPage.) */ fd = BasicOpenFile(path, O_RDWR | PG_BINARY, S_IRUSR | S_IWUSR); if (fd < 0) @@ -649,16 +654,15 @@ SelectLRUCLOGPage(int pageno) } /* - * If we find any EMPTY slot, just select that one. - * Else locate the least-recently-used slot that isn't the - * latest CLOG page. + * If we find any EMPTY slot, just select that one. Else locate + * the least-recently-used slot that isn't the latest CLOG page. */ for (slotno = 0; slotno < NUM_CLOG_BUFFERS; slotno++) { if (ClogCtl->page_status[slotno] == CLOG_PAGE_EMPTY) return slotno; if (ClogCtl->page_lru_count[slotno] > bestcount && - ClogCtl->page_number[slotno] != ClogCtl->latest_page_number) + ClogCtl->page_number[slotno] != ClogCtl->latest_page_number) { bestslot = slotno; bestcount = ClogCtl->page_lru_count[slotno]; @@ -672,10 +676,10 @@ SelectLRUCLOGPage(int pageno) return bestslot; /* - * We need to do I/O. Normal case is that we have to write it out, - * but it's possible in the worst case to have selected a read-busy - * page. In that case we use ReadCLOGPage to wait for the read to - * complete. + * We need to do I/O. Normal case is that we have to write it + * out, but it's possible in the worst case to have selected a + * read-busy page. In that case we use ReadCLOGPage to wait for + * the read to complete. */ if (ClogCtl->page_status[bestslot] == CLOG_PAGE_READ_IN_PROGRESS) (void) ReadCLOGPage(ClogCtl->page_number[bestslot]); @@ -683,9 +687,9 @@ SelectLRUCLOGPage(int pageno) WriteCLOGPage(bestslot); /* - * Now loop back and try again. This is the easiest way of dealing - * with corner cases such as the victim page being re-dirtied while - * we wrote it. + * Now loop back and try again. This is the easiest way of + * dealing with corner cases such as the victim page being + * re-dirtied while we wrote it. */ } } @@ -736,6 +740,7 @@ CheckPointCLOG(void) for (slotno = 0; slotno < NUM_CLOG_BUFFERS; slotno++) { WriteCLOGPage(slotno); + /* * We cannot assert that the slot is clean now, since another * process might have re-dirtied it already. That's okay. @@ -782,13 +787,13 @@ ExtendCLOG(TransactionId newestXact) * Remove all CLOG segments before the one holding the passed transaction ID * * When this is called, we know that the database logically contains no - * reference to transaction IDs older than oldestXact. However, we must + * reference to transaction IDs older than oldestXact. However, we must * not truncate the CLOG until we have performed a checkpoint, to ensure * that no such references remain on disk either; else a crash just after * the truncation might leave us with a problem. Since CLOG segments hold * a large number of transactions, the opportunity to actually remove a * segment is fairly rare, and so it seems best not to do the checkpoint - * unless we have confirmed that there is a removable segment. Therefore + * unless we have confirmed that there is a removable segment. Therefore * we issue the checkpoint command here, not in higher-level code as might * seem cleaner. */ @@ -813,15 +818,16 @@ TruncateCLOG(TransactionId oldestXact) /* * Scan CLOG shared memory and remove any pages preceding the cutoff * page, to ensure we won't rewrite them later. (Any dirty pages - * should have been flushed already during the checkpoint, we're - * just being extra careful here.) + * should have been flushed already during the checkpoint, we're just + * being extra careful here.) */ LWLockAcquire(CLogControlLock, LW_EXCLUSIVE); restart:; + /* - * While we are holding the lock, make an important safety check: - * the planned cutoff point must be <= the current CLOG endpoint page. + * While we are holding the lock, make an important safety check: the + * planned cutoff point must be <= the current CLOG endpoint page. * Otherwise we have already wrapped around, and proceeding with the * truncation would risk removing the current CLOG segment. */ @@ -838,6 +844,7 @@ restart:; continue; if (!CLOGPagePrecedes(ClogCtl->page_number[slotno], cutoffPage)) continue; + /* * If page is CLEAN, just change state to EMPTY (expected case). */ @@ -846,6 +853,7 @@ restart:; ClogCtl->page_status[slotno] = CLOG_PAGE_EMPTY; continue; } + /* * Hmm, we have (or may have) I/O operations acting on the page, * so we've got to wait for them to finish and then start again. @@ -928,9 +936,11 @@ CLOGPagePrecedes(int page1, int page2) TransactionId xid1; TransactionId xid2; - xid1 = (TransactionId) page1 * CLOG_XACTS_PER_PAGE; + xid1 = (TransactionId) page1 *CLOG_XACTS_PER_PAGE; + xid1 += FirstNormalTransactionId; - xid2 = (TransactionId) page2 * CLOG_XACTS_PER_PAGE; + xid2 = (TransactionId) page2 *CLOG_XACTS_PER_PAGE; + xid2 += FirstNormalTransactionId; return TransactionIdPrecedes(xid1, xid2); @@ -966,8 +976,8 @@ clog_redo(XLogRecPtr lsn, XLogRecord *record) if (info == CLOG_ZEROPAGE) { - int pageno; - int slotno; + int pageno; + int slotno; memcpy(&pageno, XLogRecGetData(record), sizeof(int)); @@ -993,7 +1003,7 @@ clog_desc(char *buf, uint8 xl_info, char *rec) if (info == CLOG_ZEROPAGE) { - int pageno; + int pageno; memcpy(&pageno, rec, sizeof(int)); sprintf(buf + strlen(buf), "zeropage: %d", pageno); |