/src/postgres/src/backend/access/gist/gistbuildbuffers.c

Source
/*-------------------------------------------------------------------------
 *
 * gistbuildbuffers.c
 *    node buffer management functions for GiST buffering build algorithm.
 *
 *
 * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *    src/backend/access/gist/gistbuildbuffers.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/gist_private.h"
#include "storage/buffile.h"
#include "storage/bufmgr.h"
#include "utils/rel.h"

static GISTNodeBufferPage *gistAllocateNewPageBuffer(GISTBuildBuffers *gfbb);
static void gistAddLoadedBuffer(GISTBuildBuffers *gfbb,
                GISTNodeBuffer *nodeBuffer);
static void gistLoadNodeBuffer(GISTBuildBuffers *gfbb,
                 GISTNodeBuffer *nodeBuffer);
static void gistUnloadNodeBuffer(GISTBuildBuffers *gfbb,
                 GISTNodeBuffer *nodeBuffer);
static void gistPlaceItupToPage(GISTNodeBufferPage *pageBuffer,
                IndexTuple itup);
static void gistGetItupFromPage(GISTNodeBufferPage *pageBuffer,
                IndexTuple *itup);
static long gistBuffersGetFreeBlock(GISTBuildBuffers *gfbb);
static void gistBuffersReleaseBlock(GISTBuildBuffers *gfbb, long blocknum);

static void ReadTempFileBlock(BufFile *file, long blknum, void *ptr);
static void WriteTempFileBlock(BufFile *file, long blknum, const void *ptr);


/*
 * Initialize GiST build buffers.
 */
GISTBuildBuffers *
gistInitBuildBuffers(int pagesPerBuffer, int levelStep, int maxLevel)
{
  GISTBuildBuffers *gfbb;
  HASHCTL   hashCtl;

  gfbb = palloc_object(GISTBuildBuffers);
  gfbb->pagesPerBuffer = pagesPerBuffer;
  gfbb->levelStep = levelStep;

  /*
   * Create a temporary file to hold buffer pages that are swapped out of
   * memory.
   */
  gfbb->pfile = BufFileCreateTemp(false);
  gfbb->nFileBlocks = 0;

  /* Initialize free page management. */
  gfbb->nFreeBlocks = 0;
  gfbb->freeBlocksLen = 32;
  gfbb->freeBlocks = palloc_array(long, gfbb->freeBlocksLen);

  /*
   * Current memory context will be used for all in-memory data structures
   * of buffers which are persistent during buffering build.
   */
  gfbb->context = CurrentMemoryContext;

  /*
   * nodeBuffersTab hash is association between index blocks and it's
   * buffers.
   */
  hashCtl.keysize = sizeof(BlockNumber);
  hashCtl.entrysize = sizeof(GISTNodeBuffer);
  hashCtl.hcxt = CurrentMemoryContext;
  gfbb->nodeBuffersTab = hash_create("gistbuildbuffers",
                     1024,
                     &hashCtl,
                     HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);

  gfbb->bufferEmptyingQueue = NIL;

  /*
   * Per-level node buffers lists for final buffers emptying process. Node
   * buffers are inserted here when they are created.
   */
  gfbb->buffersOnLevelsLen = 1;
  gfbb->buffersOnLevels = palloc_array(List *, gfbb->buffersOnLevelsLen);
  gfbb->buffersOnLevels[0] = NIL;

  /*
   * Block numbers of node buffers which last pages are currently loaded
   * into main memory.
   */
  gfbb->loadedBuffersLen = 32;
  gfbb->loadedBuffers = palloc_array(GISTNodeBuffer *, gfbb->loadedBuffersLen);
  gfbb->loadedBuffersCount = 0;

  gfbb->rootlevel = maxLevel;

  return gfbb;
}

/*
 * Returns a node buffer for given block. The buffer is created if it
 * doesn't exist yet.
 */
GISTNodeBuffer *
gistGetNodeBuffer(GISTBuildBuffers *gfbb, GISTSTATE *giststate,
          BlockNumber nodeBlocknum, int level)
{
  GISTNodeBuffer *nodeBuffer;
  bool    found;

  /* Find node buffer in hash table */
  nodeBuffer = (GISTNodeBuffer *) hash_search(gfbb->nodeBuffersTab,
                        &nodeBlocknum,
                        HASH_ENTER,
                        &found);
  if (!found)
  {
    /*
     * Node buffer wasn't found. Initialize the new buffer as empty.
     */
    MemoryContext oldcxt = MemoryContextSwitchTo(gfbb->context);

    /* nodeBuffer->nodeBlocknum is the hash key and was filled in already */
    nodeBuffer->blocksCount = 0;
    nodeBuffer->pageBlocknum = InvalidBlockNumber;
    nodeBuffer->pageBuffer = NULL;
    nodeBuffer->queuedForEmptying = false;
    nodeBuffer->isTemp = false;
    nodeBuffer->level = level;

    /*
     * Add this buffer to the list of buffers on this level. Enlarge
     * buffersOnLevels array if needed.
     */
    if (level >= gfbb->buffersOnLevelsLen)
    {
      int     i;

      gfbb->buffersOnLevels =
        (List **) repalloc(gfbb->buffersOnLevels,
                   (level + 1) * sizeof(List *));

      /* initialize the enlarged portion */
      for (i = gfbb->buffersOnLevelsLen; i <= level; i++)
        gfbb->buffersOnLevels[i] = NIL;
      gfbb->buffersOnLevelsLen = level + 1;
    }

    /*
     * Prepend the new buffer to the list of buffers on this level. It's
     * not arbitrary that the new buffer is put to the beginning of the
     * list: in the final emptying phase we loop through all buffers at
     * each level, and flush them. If a page is split during the emptying,
     * it's more efficient to flush the new split pages first, before
     * moving on to pre-existing pages on the level. The buffers just
     * created during the page split are likely still in cache, so
     * flushing them immediately is more efficient than putting them to
     * the end of the queue.
     */
    gfbb->buffersOnLevels[level] = lcons(nodeBuffer,
                       gfbb->buffersOnLevels[level]);

    MemoryContextSwitchTo(oldcxt);
  }

  return nodeBuffer;
}

/*
 * Allocate memory for a buffer page.
 */
static GISTNodeBufferPage *
gistAllocateNewPageBuffer(GISTBuildBuffers *gfbb)
{
  GISTNodeBufferPage *pageBuffer;

  pageBuffer = (GISTNodeBufferPage *) MemoryContextAllocZero(gfbb->context,
                                 BLCKSZ);
  pageBuffer->prev = InvalidBlockNumber;

  /* Set page free space */
  PAGE_FREE_SPACE(pageBuffer) = BLCKSZ - BUFFER_PAGE_DATA_OFFSET;
  return pageBuffer;
}

/*
 * Add specified buffer into loadedBuffers array.
 */
static void
gistAddLoadedBuffer(GISTBuildBuffers *gfbb, GISTNodeBuffer *nodeBuffer)
{
  /* Never add a temporary buffer to the array */
  if (nodeBuffer->isTemp)
    return;

  /* Enlarge the array if needed */
  if (gfbb->loadedBuffersCount >= gfbb->loadedBuffersLen)
  {
    gfbb->loadedBuffersLen *= 2;
    gfbb->loadedBuffers = (GISTNodeBuffer **)
      repalloc(gfbb->loadedBuffers,
           gfbb->loadedBuffersLen * sizeof(GISTNodeBuffer *));
  }

  gfbb->loadedBuffers[gfbb->loadedBuffersCount] = nodeBuffer;
  gfbb->loadedBuffersCount++;
}

/*
 * Load last page of node buffer into main memory.
 */
static void
gistLoadNodeBuffer(GISTBuildBuffers *gfbb, GISTNodeBuffer *nodeBuffer)
{
  /* Check if we really should load something */
  if (!nodeBuffer->pageBuffer && nodeBuffer->blocksCount > 0)
  {
    /* Allocate memory for page */
    nodeBuffer->pageBuffer = gistAllocateNewPageBuffer(gfbb);

    /* Read block from temporary file */
    ReadTempFileBlock(gfbb->pfile, nodeBuffer->pageBlocknum,
              nodeBuffer->pageBuffer);

    /* Mark file block as free */
    gistBuffersReleaseBlock(gfbb, nodeBuffer->pageBlocknum);

    /* Mark node buffer as loaded */
    gistAddLoadedBuffer(gfbb, nodeBuffer);
    nodeBuffer->pageBlocknum = InvalidBlockNumber;
  }
}

/*
 * Write last page of node buffer to the disk.
 */
static void
gistUnloadNodeBuffer(GISTBuildBuffers *gfbb, GISTNodeBuffer *nodeBuffer)
{
  /* Check if we have something to write */
  if (nodeBuffer->pageBuffer)
  {
    BlockNumber blkno;

    /* Get free file block */
    blkno = gistBuffersGetFreeBlock(gfbb);

    /* Write block to the temporary file */
    WriteTempFileBlock(gfbb->pfile, blkno, nodeBuffer->pageBuffer);

    /* Free memory of that page */
    pfree(nodeBuffer->pageBuffer);
    nodeBuffer->pageBuffer = NULL;

    /* Save block number */
    nodeBuffer->pageBlocknum = blkno;
  }
}

/*
 * Write last pages of all node buffers to the disk.
 */
void
gistUnloadNodeBuffers(GISTBuildBuffers *gfbb)
{
  int     i;

  /* Unload all the buffers that have a page loaded in memory. */
  for (i = 0; i < gfbb->loadedBuffersCount; i++)
    gistUnloadNodeBuffer(gfbb, gfbb->loadedBuffers[i]);

  /* Now there are no node buffers with loaded last page */
  gfbb->loadedBuffersCount = 0;
}

/*
 * Add index tuple to buffer page.
 */
static void
gistPlaceItupToPage(GISTNodeBufferPage *pageBuffer, IndexTuple itup)
{
  Size    itupsz = IndexTupleSize(itup);
  char     *ptr;

  /* There should be enough of space. */
  Assert(PAGE_FREE_SPACE(pageBuffer) >= MAXALIGN(itupsz));

  /* Reduce free space value of page to reserve a spot for the tuple. */
  PAGE_FREE_SPACE(pageBuffer) -= MAXALIGN(itupsz);

  /* Get pointer to the spot we reserved (ie. end of free space). */
  ptr = (char *) pageBuffer + BUFFER_PAGE_DATA_OFFSET
    + PAGE_FREE_SPACE(pageBuffer);

  /* Copy the index tuple there. */
  memcpy(ptr, itup, itupsz);
}

/*
 * Get last item from buffer page and remove it from page.
 */
static void
gistGetItupFromPage(GISTNodeBufferPage *pageBuffer, IndexTuple *itup)
{
  IndexTuple  ptr;
  Size    itupsz;

  Assert(!PAGE_IS_EMPTY(pageBuffer)); /* Page shouldn't be empty */

  /* Get pointer to last index tuple */
  ptr = (IndexTuple) ((char *) pageBuffer
            + BUFFER_PAGE_DATA_OFFSET
            + PAGE_FREE_SPACE(pageBuffer));
  itupsz = IndexTupleSize(ptr);

  /* Make a copy of the tuple */
  *itup = (IndexTuple) palloc(itupsz);
  memcpy(*itup, ptr, itupsz);

  /* Mark the space used by the tuple as free */
  PAGE_FREE_SPACE(pageBuffer) += MAXALIGN(itupsz);
}

/*
 * Push an index tuple to node buffer.
 */
void
gistPushItupToNodeBuffer(GISTBuildBuffers *gfbb, GISTNodeBuffer *nodeBuffer,
             IndexTuple itup)
{
  /*
   * Most part of memory operations will be in buffering build persistent
   * context. So, let's switch to it.
   */
  MemoryContext oldcxt = MemoryContextSwitchTo(gfbb->context);

  /*
   * If the buffer is currently empty, create the first page.
   */
  if (nodeBuffer->blocksCount == 0)
  {
    nodeBuffer->pageBuffer = gistAllocateNewPageBuffer(gfbb);
    nodeBuffer->blocksCount = 1;
    gistAddLoadedBuffer(gfbb, nodeBuffer);
  }

  /* Load last page of node buffer if it wasn't in memory already */
  if (!nodeBuffer->pageBuffer)
    gistLoadNodeBuffer(gfbb, nodeBuffer);

  /*
   * Check if there is enough space on the last page for the tuple.
   */
  if (PAGE_NO_SPACE(nodeBuffer->pageBuffer, itup))
  {
    /*
     * Nope. Swap previous block to disk and allocate a new one.
     */
    BlockNumber blkno;

    /* Write filled page to the disk */
    blkno = gistBuffersGetFreeBlock(gfbb);
    WriteTempFileBlock(gfbb->pfile, blkno, nodeBuffer->pageBuffer);

    /*
     * Reset the in-memory page as empty, and link the previous block to
     * the new page by storing its block number in the prev-link.
     */
    PAGE_FREE_SPACE(nodeBuffer->pageBuffer) =
      BLCKSZ - MAXALIGN(offsetof(GISTNodeBufferPage, tupledata));
    nodeBuffer->pageBuffer->prev = blkno;

    /* We've just added one more page */
    nodeBuffer->blocksCount++;
  }

  gistPlaceItupToPage(nodeBuffer->pageBuffer, itup);

  /*
   * If the buffer just overflowed, add it to the emptying queue.
   */
  if (BUFFER_HALF_FILLED(nodeBuffer, gfbb) && !nodeBuffer->queuedForEmptying)
  {
    gfbb->bufferEmptyingQueue = lcons(nodeBuffer,
                      gfbb->bufferEmptyingQueue);
    nodeBuffer->queuedForEmptying = true;
  }

  /* Restore memory context */
  MemoryContextSwitchTo(oldcxt);
}

/*
 * Removes one index tuple from node buffer. Returns true if success and false
 * if node buffer is empty.
 */
bool
gistPopItupFromNodeBuffer(GISTBuildBuffers *gfbb, GISTNodeBuffer *nodeBuffer,
              IndexTuple *itup)
{
  /*
   * If node buffer is empty then return false.
   */
  if (nodeBuffer->blocksCount <= 0)
    return false;

  /* Load last page of node buffer if needed */
  if (!nodeBuffer->pageBuffer)
    gistLoadNodeBuffer(gfbb, nodeBuffer);

  /*
   * Get index tuple from last non-empty page.
   */
  gistGetItupFromPage(nodeBuffer->pageBuffer, itup);

  /*
   * If we just removed the last tuple from the page, fetch previous page on
   * this node buffer (if any).
   */
  if (PAGE_IS_EMPTY(nodeBuffer->pageBuffer))
  {
    BlockNumber prevblkno;

    /*
     * blocksCount includes the page in pageBuffer, so decrease it now.
     */
    nodeBuffer->blocksCount--;

    /*
     * If there's more pages, fetch previous one.
     */
    prevblkno = nodeBuffer->pageBuffer->prev;
    if (prevblkno != InvalidBlockNumber)
    {
      /* There is a previous page. Fetch it. */
      Assert(nodeBuffer->blocksCount > 0);
      ReadTempFileBlock(gfbb->pfile, prevblkno, nodeBuffer->pageBuffer);

      /*
       * Now that we've read the block in memory, we can release its
       * on-disk block for reuse.
       */
      gistBuffersReleaseBlock(gfbb, prevblkno);
    }
    else
    {
      /* No more pages. Free memory. */
      Assert(nodeBuffer->blocksCount == 0);
      pfree(nodeBuffer->pageBuffer);
      nodeBuffer->pageBuffer = NULL;
    }
  }
  return true;
}

/*
 * Select a currently unused block for writing to.
 */
static long
gistBuffersGetFreeBlock(GISTBuildBuffers *gfbb)
{
  /*
   * If there are multiple free blocks, we select the one appearing last in
   * freeBlocks[].  If there are none, assign the next block at the end of
   * the file (causing the file to be extended).
   */
  if (gfbb->nFreeBlocks > 0)
    return gfbb->freeBlocks[--gfbb->nFreeBlocks];
  else
    return gfbb->nFileBlocks++;
}

/*
 * Return a block# to the freelist.
 */
static void
gistBuffersReleaseBlock(GISTBuildBuffers *gfbb, long blocknum)
{
  int     ndx;

  /* Enlarge freeBlocks array if full. */
  if (gfbb->nFreeBlocks >= gfbb->freeBlocksLen)
  {
    gfbb->freeBlocksLen *= 2;
    gfbb->freeBlocks = (long *) repalloc(gfbb->freeBlocks,
                       gfbb->freeBlocksLen *
                       sizeof(long));
  }

  /* Add blocknum to array */
  ndx = gfbb->nFreeBlocks++;
  gfbb->freeBlocks[ndx] = blocknum;
}

/*
 * Free buffering build data structure.
 */
void
gistFreeBuildBuffers(GISTBuildBuffers *gfbb)
{
  /* Close buffers file. */
  BufFileClose(gfbb->pfile);

  /* All other things will be freed on memory context release */
}

/*
 * Data structure representing information about node buffer for index tuples
 * relocation from split node buffer.
 */
typedef struct
{
  GISTENTRY entry[INDEX_MAX_KEYS];
  bool    isnull[INDEX_MAX_KEYS];
  GISTPageSplitInfo *splitinfo;
  GISTNodeBuffer *nodeBuffer;
} RelocationBufferInfo;

/*
 * At page split, distribute tuples from the buffer of the split page to
 * new buffers for the created page halves. This also adjusts the downlinks
 * in 'splitinfo' to include the tuples in the buffers.
 */
void
gistRelocateBuildBuffersOnSplit(GISTBuildBuffers *gfbb, GISTSTATE *giststate,
                Relation r, int level,
                Buffer buffer, List *splitinfo)
{
  RelocationBufferInfo *relocationBuffersInfos;
  bool    found;
  GISTNodeBuffer *nodeBuffer;
  BlockNumber blocknum;
  IndexTuple  itup;
  int     splitPagesCount = 0;
  GISTENTRY entry[INDEX_MAX_KEYS];
  bool    isnull[INDEX_MAX_KEYS];
  GISTNodeBuffer oldBuf;
  ListCell   *lc;

  /* If the split page doesn't have buffers, we have nothing to do. */
  if (!LEVEL_HAS_BUFFERS(level, gfbb))
    return;

  /*
   * Get the node buffer of the split page.
   */
  blocknum = BufferGetBlockNumber(buffer);
  nodeBuffer = hash_search(gfbb->nodeBuffersTab, &blocknum,
               HASH_FIND, &found);
  if (!found)
  {
    /* The page has no buffer, so we have nothing to do. */
    return;
  }

  /*
   * Make a copy of the old buffer, as we're going reuse it as the buffer
   * for the new left page, which is on the same block as the old page.
   * That's not true for the root page, but that's fine because we never
   * have a buffer on the root page anyway. The original algorithm as
   * described by Arge et al did, but it's of no use, as you might as well
   * read the tuples straight from the heap instead of the root buffer.
   */
  Assert(blocknum != GIST_ROOT_BLKNO);
  memcpy(&oldBuf, nodeBuffer, sizeof(GISTNodeBuffer));
  oldBuf.isTemp = true;

  /* Reset the old buffer, used for the new left page from now on */
  nodeBuffer->blocksCount = 0;
  nodeBuffer->pageBuffer = NULL;
  nodeBuffer->pageBlocknum = InvalidBlockNumber;

  /*
   * Allocate memory for information about relocation buffers.
   */
  splitPagesCount = list_length(splitinfo);
  relocationBuffersInfos = palloc_array(RelocationBufferInfo, splitPagesCount);

  /*
   * Fill relocation buffers information for node buffers of pages produced
   * by split.
   */
  foreach(lc, splitinfo)
  {
    GISTPageSplitInfo *si = (GISTPageSplitInfo *) lfirst(lc);
    GISTNodeBuffer *newNodeBuffer;
    int     i = foreach_current_index(lc);

    /* Decompress parent index tuple of node buffer page. */
    gistDeCompressAtt(giststate, r,
              si->downlink, NULL, (OffsetNumber) 0,
              relocationBuffersInfos[i].entry,
              relocationBuffersInfos[i].isnull);

    /*
     * Create a node buffer for the page. The leftmost half is on the same
     * block as the old page before split, so for the leftmost half this
     * will return the original buffer. The tuples on the original buffer
     * were relinked to the temporary buffer, so the original one is now
     * empty.
     */
    newNodeBuffer = gistGetNodeBuffer(gfbb, giststate, BufferGetBlockNumber(si->buf), level);

    relocationBuffersInfos[i].nodeBuffer = newNodeBuffer;
    relocationBuffersInfos[i].splitinfo = si;
  }

  /*
   * Loop through all index tuples in the buffer of the page being split,
   * moving them to buffers for the new pages.  We try to move each tuple to
   * the page that will result in the lowest penalty for the leading column
   * or, in the case of a tie, the lowest penalty for the earliest column
   * that is not tied.
   *
   * The page searching logic is very similar to gistchoose().
   */
  while (gistPopItupFromNodeBuffer(gfbb, &oldBuf, &itup))
  {
    float   best_penalty[INDEX_MAX_KEYS];
    int     i,
          which;
    IndexTuple  newtup;
    RelocationBufferInfo *targetBufferInfo;

    gistDeCompressAtt(giststate, r,
              itup, NULL, (OffsetNumber) 0, entry, isnull);

    /* default to using first page (shouldn't matter) */
    which = 0;

    /*
     * best_penalty[j] is the best penalty we have seen so far for column
     * j, or -1 when we haven't yet examined column j.  Array entries to
     * the right of the first -1 are undefined.
     */
    best_penalty[0] = -1;

    /*
     * Loop over possible target pages, looking for one to move this tuple
     * to.
     */
    for (i = 0; i < splitPagesCount; i++)
    {
      RelocationBufferInfo *splitPageInfo = &relocationBuffersInfos[i];
      bool    zero_penalty;
      int     j;

      zero_penalty = true;

      /* Loop over index attributes. */
      for (j = 0; j < IndexRelationGetNumberOfKeyAttributes(r); j++)
      {
        float   usize;

        /* Compute penalty for this column. */
        usize = gistpenalty(giststate, j,
                  &splitPageInfo->entry[j],
                  splitPageInfo->isnull[j],
                  &entry[j], isnull[j]);
        if (usize > 0)
          zero_penalty = false;

        if (best_penalty[j] < 0 || usize < best_penalty[j])
        {
          /*
           * New best penalty for column.  Tentatively select this
           * page as the target, and record the best penalty.  Then
           * reset the next column's penalty to "unknown" (and
           * indirectly, the same for all the ones to its right).
           * This will force us to adopt this page's penalty values
           * as the best for all the remaining columns during
           * subsequent loop iterations.
           */
          which = i;
          best_penalty[j] = usize;

          if (j < IndexRelationGetNumberOfKeyAttributes(r) - 1)
            best_penalty[j + 1] = -1;
        }
        else if (best_penalty[j] == usize)
        {
          /*
           * The current page is exactly as good for this column as
           * the best page seen so far.  The next iteration of this
           * loop will compare the next column.
           */
        }
        else
        {
          /*
           * The current page is worse for this column than the best
           * page seen so far.  Skip the remaining columns and move
           * on to the next page, if any.
           */
          zero_penalty = false;  /* so outer loop won't exit */
          break;
        }
      }

      /*
       * If we find a page with zero penalty for all columns, there's no
       * need to examine remaining pages; just break out of the loop and
       * return it.
       */
      if (zero_penalty)
        break;
    }

    /* OK, "which" is the page index to push the tuple to */
    targetBufferInfo = &relocationBuffersInfos[which];

    /* Push item to selected node buffer */
    gistPushItupToNodeBuffer(gfbb, targetBufferInfo->nodeBuffer, itup);

    /* Adjust the downlink for this page, if needed. */
    newtup = gistgetadjusted(r, targetBufferInfo->splitinfo->downlink,
                 itup, giststate);
    if (newtup)
    {
      gistDeCompressAtt(giststate, r,
                newtup, NULL, (OffsetNumber) 0,
                targetBufferInfo->entry,
                targetBufferInfo->isnull);

      targetBufferInfo->splitinfo->downlink = newtup;
    }
  }

  pfree(relocationBuffersInfos);
}


/*
 * Wrappers around BufFile operations. The main difference is that these
 * wrappers report errors with ereport(), so that the callers don't need
 * to check the return code.
 */

static void
ReadTempFileBlock(BufFile *file, long blknum, void *ptr)
{
  if (BufFileSeekBlock(file, blknum) != 0)
    elog(ERROR, "could not seek to block %ld in temporary file", blknum);
  BufFileReadExact(file, ptr, BLCKSZ);
}

static void
WriteTempFileBlock(BufFile *file, long blknum, const void *ptr)
{
  if (BufFileSeekBlock(file, blknum) != 0)
    elog(ERROR, "could not seek to block %ld in temporary file", blknum);
  BufFileWrite(file, ptr, BLCKSZ);
}

Coverage Report

Created: 2026-08-14 06:37