generic_xlog.c File Reference

#include "postgres.h"
#include "access/bufmask.h"
#include "access/generic_xlog.h"
#include "access/xlogutils.h"
#include "miscadmin.h"

Include dependency graph for generic_xlog.c:

Go to the source code of this file.

Data Structures
struct	PageData
struct	GenericXLogState

Macros
#define	FRAGMENT_HEADER_SIZE   (2 * sizeof(OffsetNumber))
#define	MATCH_THRESHOLD   FRAGMENT_HEADER_SIZE
#define	MAX_DELTA_SIZE   (BLCKSZ + 2 * FRAGMENT_HEADER_SIZE)

Functions
static void	writeFragment (PageData *pageData, OffsetNumber offset, OffsetNumber length, const char *data)
static void	computeRegionDelta (PageData *pageData, const char *curpage, const char *targetpage, int targetStart, int targetEnd, int validStart, int validEnd)
static void	computeDelta (PageData *pageData, Page curpage, Page targetpage)
static void	applyPageRedo (Page page, const char *delta, Size deltaSize)
GenericXLogState *	GenericXLogStart (Relation relation)
Page	GenericXLogRegisterBuffer (GenericXLogState *state, Buffer buffer, int flags)
XLogRecPtr	GenericXLogFinish (GenericXLogState *state)
void	GenericXLogAbort (GenericXLogState *state)
void	generic_redo (XLogReaderState *record)
void	generic_mask (char *page, BlockNumber blkno)

Macro Definition Documentation

FRAGMENT_HEADER_SIZE

#define FRAGMENT_HEADER_SIZE   (2 * sizeof(OffsetNumber))

Definition at line 45 of file generic_xlog.c.

MATCH_THRESHOLD

#define MATCH_THRESHOLD   FRAGMENT_HEADER_SIZE

Definition at line 46 of file generic_xlog.c.

MAX_DELTA_SIZE

#define MAX_DELTA_SIZE   (BLCKSZ + 2 * FRAGMENT_HEADER_SIZE)

Definition at line 47 of file generic_xlog.c.

Function Documentation

applyPageRedo()

static void applyPageRedo ( Page  page, const char *  delta, Size  deltaSize  )

static

Definition at line 453 of file generic_xlog.c.

{
    const char *ptr = delta;
    const char *end = delta + deltaSize;
 
    while (ptr < end)
    {
        OffsetNumber offset,
                    length;
 
        memcpy(&offset, ptr, sizeof(offset));
        ptr += sizeof(offset);
        memcpy(&length, ptr, sizeof(length));
        ptr += sizeof(length);
 
        memcpy(page + offset, ptr, length);
 
        ptr += length;
    }
}

Referenced by computeDelta(), and generic_redo().

computeDelta()

static void computeDelta ( PageData *  pageData, Page  curpage, Page  targetpage  )

static

Definition at line 228 of file generic_xlog.c.

{
    int         targetLower = ((PageHeader) targetpage)->pd_lower,
                targetUpper = ((PageHeader) targetpage)->pd_upper,
                curLower = ((PageHeader) curpage)->pd_lower,
                curUpper = ((PageHeader) curpage)->pd_upper;
 
    pageData->deltaLen = 0;
 
    /* Compute delta records for lower part of page ... */
    computeRegionDelta(pageData, curpage, targetpage,
                       0, targetLower,
                       0, curLower);
    /* ... and for upper part, ignoring what's between */
    computeRegionDelta(pageData, curpage, targetpage,
                       targetUpper, BLCKSZ,
                       curUpper, BLCKSZ);
 
    /*
     * If xlog debug is enabled, then check produced delta.  Result of delta
     * application to curpage should be equivalent to targetpage.
     */
#ifdef WAL_DEBUG
    if (XLOG_DEBUG)
    {
        PGAlignedBlock tmp;
 
        memcpy(tmp.data, curpage, BLCKSZ);
        applyPageRedo(tmp.data, pageData->delta, pageData->deltaLen);
        if (memcmp(tmp.data, targetpage, targetLower) != 0 ||
            memcmp(tmp.data + targetUpper, targetpage + targetUpper,
                   BLCKSZ - targetUpper) != 0)
            elog(ERROR, "result of generic xlog apply does not match");
    }
#endif
}

References applyPageRedo(), computeRegionDelta(), PGAlignedBlock::data, PageData::delta, PageData::deltaLen, elog, and ERROR.

Referenced by GenericXLogFinish().

computeRegionDelta()

static void computeRegionDelta ( PageData *  pageData, const char *  curpage, const char *  targetpage, int  targetStart, int  targetEnd, int  validStart, int  validEnd  )

static

Definition at line 121 of file generic_xlog.c.

{
    int         i,
                loopEnd,
                fragmentBegin = -1,
                fragmentEnd = -1;
 
    /* Deal with any invalid start region by including it in first fragment */
    if (validStart > targetStart)
    {
        fragmentBegin = targetStart;
        targetStart = validStart;
    }
 
    /* We'll deal with any invalid end region after the main loop */
    loopEnd = Min(targetEnd, validEnd);
 
    /* Examine all the potentially matchable bytes */
    i = targetStart;
    while (i < loopEnd)
    {
        if (curpage[i] != targetpage[i])
        {
            /* On unmatched byte, start new fragment if not already in one */
            if (fragmentBegin < 0)
                fragmentBegin = i;
            /* Mark unmatched-data endpoint as uncertain */
            fragmentEnd = -1;
            /* Extend the fragment as far as possible in a tight loop */
            i++;
            while (i < loopEnd && curpage[i] != targetpage[i])
                i++;
            if (i >= loopEnd)
                break;
        }
 
        /* Found a matched byte, so remember end of unmatched fragment */
        fragmentEnd = i;
 
        /*
         * Extend the match as far as possible in a tight loop.  (On typical
         * workloads, this inner loop is the bulk of this function's runtime.)
         */
        i++;
        while (i < loopEnd && curpage[i] == targetpage[i])
            i++;
 
        /*
         * There are several possible cases at this point:
         *
         * 1. We have no unwritten fragment (fragmentBegin < 0).  There's
         * nothing to write; and it doesn't matter what fragmentEnd is.
         *
         * 2. We found more than MATCH_THRESHOLD consecutive matching bytes.
         * Dump out the unwritten fragment, stopping at fragmentEnd.
         *
         * 3. The match extends to loopEnd.  We'll do nothing here, exit the
         * loop, and then dump the unwritten fragment, after merging it with
         * the invalid end region if any.  If we don't so merge, fragmentEnd
         * establishes how much the final writeFragment call needs to write.
         *
         * 4. We found an unmatched byte before loopEnd.  The loop will repeat
         * and will enter the unmatched-byte stanza above.  So in this case
         * also, it doesn't matter what fragmentEnd is.  The matched bytes
         * will get merged into the continuing unmatched fragment.
         *
         * Only in case 3 do we reach the bottom of the loop with a meaningful
         * fragmentEnd value, which is why it's OK that we unconditionally
         * assign "fragmentEnd = i" above.
         */
        if (fragmentBegin >= 0 && i - fragmentEnd > MATCH_THRESHOLD)
        {
            writeFragment(pageData, fragmentBegin,
                          fragmentEnd - fragmentBegin,
                          targetpage + fragmentBegin);
            fragmentBegin = -1;
            fragmentEnd = -1;   /* not really necessary */
        }
    }
 
    /* Deal with any invalid end region by including it in final fragment */
    if (loopEnd < targetEnd)
    {
        if (fragmentBegin < 0)
            fragmentBegin = loopEnd;
        fragmentEnd = targetEnd;
    }
 
    /* Write final fragment if any */
    if (fragmentBegin >= 0)
    {
        if (fragmentEnd < 0)
            fragmentEnd = targetEnd;
        writeFragment(pageData, fragmentBegin,
                      fragmentEnd - fragmentBegin,
                      targetpage + fragmentBegin);
    }
}

References i, MATCH_THRESHOLD, Min, and writeFragment().

Referenced by computeDelta().

generic_mask()

void generic_mask	(	char *	page,
		BlockNumber	blkno
	)

Definition at line 539 of file generic_xlog.c.

{
    mask_page_lsn_and_checksum(page);
 
    mask_unused_space(page);
}

References mask_page_lsn_and_checksum(), and mask_unused_space().

generic_redo()

void generic_redo

(

XLogReaderState *

record

)

Definition at line 478 of file generic_xlog.c.

{
    XLogRecPtr  lsn = record->EndRecPtr;
    Buffer      buffers[MAX_GENERIC_XLOG_PAGES];
    uint8       block_id;
 
    /* Protect limited size of buffers[] array */
    Assert(XLogRecMaxBlockId(record) < MAX_GENERIC_XLOG_PAGES);
 
    /* Iterate over blocks */
    for (block_id = 0; block_id <= XLogRecMaxBlockId(record); block_id++)
    {
        XLogRedoAction action;
 
        if (!XLogRecHasBlockRef(record, block_id))
        {
            buffers[block_id] = InvalidBuffer;
            continue;
        }
 
        action = XLogReadBufferForRedo(record, block_id, &buffers[block_id]);
 
        /* Apply redo to given block if needed */
        if (action == BLK_NEEDS_REDO)
        {
            Page        page;
            PageHeader  pageHeader;
            char       *blockDelta;
            Size        blockDeltaSize;
 
            page = BufferGetPage(buffers[block_id]);
            blockDelta = XLogRecGetBlockData(record, block_id, &blockDeltaSize);
            applyPageRedo(page, blockDelta, blockDeltaSize);
 
            /*
             * Since the delta contains no information about what's in the
             * "hole" between pd_lower and pd_upper, set that to zero to
             * ensure we produce the same page state that application of the
             * logged action by GenericXLogFinish did.
             */
            pageHeader = (PageHeader) page;
            memset(page + pageHeader->pd_lower, 0,
                   pageHeader->pd_upper - pageHeader->pd_lower);
 
            PageSetLSN(page, lsn);
            MarkBufferDirty(buffers[block_id]);
        }
    }
 
    /* Changes are done: unlock and release all buffers */
    for (block_id = 0; block_id <= XLogRecMaxBlockId(record); block_id++)
    {
        if (BufferIsValid(buffers[block_id]))
            UnlockReleaseBuffer(buffers[block_id]);
    }
}

References generate_unaccent_rules::action, applyPageRedo(), Assert, BLK_NEEDS_REDO, BufferGetPage(), BufferIsValid(), XLogReaderState::EndRecPtr, InvalidBuffer, MarkBufferDirty(), MAX_GENERIC_XLOG_PAGES, PageSetLSN(), PageHeaderData::pd_lower, PageHeaderData::pd_upper, UnlockReleaseBuffer(), XLogReadBufferForRedo(), XLogRecGetBlockData(), XLogRecHasBlockRef, and XLogRecMaxBlockId.

GenericXLogAbort()

void GenericXLogAbort

(

GenericXLogState *

state

)

Definition at line 444 of file generic_xlog.c.

{
    pfree(state);
}

References pfree().

Referenced by blbulkdelete(), and blinsert().

GenericXLogFinish()

XLogRecPtr GenericXLogFinish

(

GenericXLogState *

state

)

Definition at line 337 of file generic_xlog.c.

{
    XLogRecPtr  lsn;
    int         i;
 
    if (state->isLogged)
    {
        /* Logged relation: make xlog record in critical section. */
        XLogBeginInsert();
 
        START_CRIT_SECTION();
 
        /*
         * Compute deltas if necessary, write changes to buffers, mark buffers
         * dirty, and register changes.
         */
        for (i = 0; i < MAX_GENERIC_XLOG_PAGES; i++)
        {
            PageData   *pageData = &state->pages[i];
            Page        page;
            PageHeader  pageHeader;
 
            if (BufferIsInvalid(pageData->buffer))
                continue;
 
            page = BufferGetPage(pageData->buffer);
            pageHeader = (PageHeader) pageData->image;
 
            /*
             * Compute delta while we still have both the unmodified page and
             * the new image. Not needed if we are logging the full image.
             */
            if (!(pageData->flags & GENERIC_XLOG_FULL_IMAGE))
                computeDelta(pageData, page, (Page) pageData->image);
 
            /*
             * Apply the image, being careful to zero the "hole" between
             * pd_lower and pd_upper in order to avoid divergence between
             * actual page state and what replay would produce.
             */
            memcpy(page, pageData->image, pageHeader->pd_lower);
            memset(page + pageHeader->pd_lower, 0,
                   pageHeader->pd_upper - pageHeader->pd_lower);
            memcpy(page + pageHeader->pd_upper,
                   pageData->image + pageHeader->pd_upper,
                   BLCKSZ - pageHeader->pd_upper);
 
            MarkBufferDirty(pageData->buffer);
 
            if (pageData->flags & GENERIC_XLOG_FULL_IMAGE)
            {
                XLogRegisterBuffer(i, pageData->buffer,
                                   REGBUF_FORCE_IMAGE | REGBUF_STANDARD);
            }
            else
            {
                XLogRegisterBuffer(i, pageData->buffer, REGBUF_STANDARD);
                XLogRegisterBufData(i, pageData->delta, pageData->deltaLen);
            }
        }
 
        /* Insert xlog record */
        lsn = XLogInsert(RM_GENERIC_ID, 0);
 
        /* Set LSN */
        for (i = 0; i < MAX_GENERIC_XLOG_PAGES; i++)
        {
            PageData   *pageData = &state->pages[i];
 
            if (BufferIsInvalid(pageData->buffer))
                continue;
            PageSetLSN(BufferGetPage(pageData->buffer), lsn);
        }
        END_CRIT_SECTION();
    }
    else
    {
        /* Unlogged relation: skip xlog-related stuff */
        START_CRIT_SECTION();
        for (i = 0; i < MAX_GENERIC_XLOG_PAGES; i++)
        {
            PageData   *pageData = &state->pages[i];
 
            if (BufferIsInvalid(pageData->buffer))
                continue;
            memcpy(BufferGetPage(pageData->buffer),
                   pageData->image,
                   BLCKSZ);
            /* We don't worry about zeroing the "hole" in this case */
            MarkBufferDirty(pageData->buffer);
        }
        END_CRIT_SECTION();
        /* We don't have a LSN to return, in this case */
        lsn = InvalidXLogRecPtr;
    }
 
    pfree(state);
 
    return lsn;
}

References PageData::buffer, BufferGetPage(), BufferIsInvalid, computeDelta(), PageData::delta, PageData::deltaLen, END_CRIT_SECTION, PageData::flags, GENERIC_XLOG_FULL_IMAGE, i, if(), PageData::image, InvalidXLogRecPtr, MarkBufferDirty(), MAX_GENERIC_XLOG_PAGES, PageSetLSN(), PageHeaderData::pd_lower, PageHeaderData::pd_upper, pfree(), REGBUF_FORCE_IMAGE, REGBUF_STANDARD, START_CRIT_SECTION, XLogBeginInsert(), XLogInsert(), XLogRegisterBufData(), and XLogRegisterBuffer().

Referenced by blbulkdelete(), blinsert(), BloomInitMetapage(), and flushCachedPage().

GenericXLogRegisterBuffer()

Page GenericXLogRegisterBuffer	(	GenericXLogState *	state,
		Buffer	buffer,
		int	flags
	)

Definition at line 299 of file generic_xlog.c.

{
    int         block_id;
 
    /* Search array for existing entry or first unused slot */
    for (block_id = 0; block_id < MAX_GENERIC_XLOG_PAGES; block_id++)
    {
        PageData   *page = &state->pages[block_id];
 
        if (BufferIsInvalid(page->buffer))
        {
            /* Empty slot, so use it (there cannot be a match later) */
            page->buffer = buffer;
            page->flags = flags;
            memcpy(page->image, BufferGetPage(buffer), BLCKSZ);
            return (Page) page->image;
        }
        else if (page->buffer == buffer)
        {
            /*
             * Buffer is already registered.  Just return the image, which is
             * already prepared.
             */
            return (Page) page->image;
        }
    }
 
    elog(ERROR, "maximum number %d of generic xlog buffers is exceeded",
         MAX_GENERIC_XLOG_PAGES);
    /* keep compiler quiet */
    return NULL;
}

References PageData::buffer, BufferGetPage(), BufferIsInvalid, elog, ERROR, PageData::flags, PageData::image, and MAX_GENERIC_XLOG_PAGES.

Referenced by blbulkdelete(), blinsert(), BloomInitMetapage(), and flushCachedPage().

GenericXLogStart()

GenericXLogState* GenericXLogStart

(

Relation

relation

)

Definition at line 269 of file generic_xlog.c.

{
    GenericXLogState *state;
    int         i;
 
    state = (GenericXLogState *) palloc_aligned(sizeof(GenericXLogState),
                                                PG_IO_ALIGN_SIZE,
                                                0);
    state->isLogged = RelationNeedsWAL(relation);
 
    for (i = 0; i < MAX_GENERIC_XLOG_PAGES; i++)
    {
        state->pages[i].image = state->images[i].data;
        state->pages[i].buffer = InvalidBuffer;
    }
 
    return state;
}

References i, InvalidBuffer, MAX_GENERIC_XLOG_PAGES, palloc_aligned(), PG_IO_ALIGN_SIZE, and RelationNeedsWAL.

Referenced by blbulkdelete(), blinsert(), BloomInitMetapage(), and flushCachedPage().

writeFragment()

static void writeFragment ( PageData *  pageData, OffsetNumber  offset, OffsetNumber  length, const char *  data  )

static

Definition at line 90 of file generic_xlog.c.

{
    char       *ptr = pageData->delta + pageData->deltaLen;
 
    /* Verify we have enough space */
    Assert(pageData->deltaLen + sizeof(offset) +
           sizeof(length) + length <= sizeof(pageData->delta));
 
    /* Write fragment data */
    memcpy(ptr, &offset, sizeof(offset));
    ptr += sizeof(offset);
    memcpy(ptr, &length, sizeof(length));
    ptr += sizeof(length);
    memcpy(ptr, data, length);
    ptr += length;
 
    pageData->deltaLen = ptr - pageData->delta;
}

References Assert, data, PageData::delta, and PageData::deltaLen.

Referenced by computeRegionDelta().