2 * Copyright (c) 1996-1998, Index Data.
3 * See the file LICENSE for details.
4 * Sebastian Hammer, Adam Dickmeiss, Heikki Levanto
16 struct isc_merge_block {
17 int offset; /* offset in r_buf */
18 int block; /* block number of file (0 if none) */
19 int dirty; /* block is different from that on file */
22 static void opt_blocks (ISAMC is, struct isc_merge_block *mb, int ptr,
26 for (i = 0; i<ptr; i++)
29 if (no_dirty*4 < ptr*3)
32 for (i = 0; i<ptr; i++)
34 int tmp, j, j_min = -1;
35 for (j = i; j<ptr; j++)
37 if (j_min < 0 || mb[j_min].block > mb[j].block)
41 tmp = mb[j_min].block;
42 mb[j_min].block = mb[i].block;
50 static void flush_blocks (ISAMC is, struct isc_merge_block *mb, int ptr,
51 char *r_buf, int *firstpos, int cat, int last,
56 for (i = 0; i<ptr; i++)
58 /* consider this block number */
61 mb[i].block = isc_alloc_block (is, cat);
65 /* consider next block pointer */
66 if (last && i == ptr-1)
68 else if (!mb[i+1].block)
70 mb[i+1].block = isc_alloc_block (is, cat);
76 for (i = 0; i<ptr; i++)
79 ISAMC_BLOCK_SIZE ssize = mb[i+1].offset - mb[i].offset;
83 /* skip rest if not dirty */
88 *firstpos = mb[i].block;
89 if (is->method->debug > 2)
90 logf (LOG_LOG, "isc: skip ptr=%d size=%d %d %d",
91 i, ssize, cat, mb[i].block);
92 ++(is->files[cat].no_skip_writes);
99 *firstpos = mb[i].block;
100 src = r_buf + mb[i].offset - ISAMC_BLOCK_OFFSET_1;
101 ssize += ISAMC_BLOCK_OFFSET_1;
103 memcpy (src+sizeof(int)+sizeof(ssize), numkeys,
105 if (is->method->debug > 2)
106 logf (LOG_LOG, "isc: flush ptr=%d numk=%d size=%d nextpos=%d",
107 i, *numkeys, (int) ssize, mb[i+1].block);
111 src = r_buf + mb[i].offset - ISAMC_BLOCK_OFFSET_N;
112 ssize += ISAMC_BLOCK_OFFSET_N;
113 if (is->method->debug > 2)
114 logf (LOG_LOG, "isc: flush ptr=%d size=%d nextpos=%d",
115 i, (int) ssize, mb[i+1].block);
117 memcpy (src, &mb[i+1].block, sizeof(int));
118 memcpy (src+sizeof(int), &ssize, sizeof(ssize));
119 isc_write_block (is, cat, mb[i].block, src);
123 static int get_border (ISAMC is, struct isc_merge_block *mb, int ptr,
124 int cat, int firstpos)
126 /* Border set to initial fill or block size depending on
127 whether we are creating a new one or updating and old one.
130 int fill = mb[ptr].block ? is->method->filecat[cat].bsize :
131 is->method->filecat[cat].ifill;
132 int off = (ptr||firstpos) ? ISAMC_BLOCK_OFFSET_N : ISAMC_BLOCK_OFFSET_1;
136 return mb[ptr].offset + fill - off;
139 ISAMC_P isc_merge (ISAMC is, ISAMC_P ipos, ISAMC_I data)
142 char i_item[128], *i_item_ptr;
143 int i_more, i_mode, i;
146 char f_item[128], *f_item_ptr;
149 int debug = is->method->debug;
151 struct isc_merge_block mb[200];
155 char r_item_buf[128]; /* temporary result output */
156 char *r_buf; /* block with resulting data */
157 int r_offset = 0; /* current offset in r_buf */
158 int ptr = 0; /* pointer */
159 void *r_clientData; /* encode client data */
163 r_clientData = (*is->method->code_start)(ISAMC_ENCODE);
164 r_buf = is->merge_buf + 128;
166 pp = isc_pp_open (is, ipos);
167 /* read first item from file. make sure f_more indicates no boundary */
169 f_more = isc_read_item (pp, &f_item_ptr);
175 logf (LOG_LOG, "isc: isc_merge begin %d %d", cat, pp->pos);
177 /* read first item from i */
179 i_more = (*data->read_item)(data->clientData, &i_item_ptr, &i_mode);
181 mb[ptr].block = pp->pos; /* is zero if no block on disk */
185 border = get_border (is, mb, ptr, cat, firstpos);
186 while (i_more || f_more)
188 char *r_item = r_item_buf;
193 /* block to block boundary in the original file. */
197 /* the resulting output is of the same category as the
200 if (r_offset <= mb[ptr].offset +is->method->filecat[cat].mfill)
202 /* the resulting output block is too small/empty. Delete
203 the original (if any)
206 logf (LOG_LOG, "isc: release A");
208 isc_release_block (is, pp->cat, mb[ptr].block);
209 mb[ptr].block = pp->pos;
217 /* indicate new boundary based on the original file */
218 mb[++ptr].block = pp->pos;
219 mb[ptr].dirty = last_dirty;
220 mb[ptr].offset = r_offset;
222 logf (LOG_LOG, "isc: bound ptr=%d,offset=%d",
224 if (cat==is->max_cat && ptr >= is->method->max_blocks_mem)
226 /* We are dealing with block(s) of max size. Block(s)
227 except 1 will be flushed.
230 logf (LOG_LOG, "isc: flush A %d sections", ptr);
231 flush_blocks (is, mb, ptr-1, r_buf, &firstpos, cat,
233 mb[0].block = mb[ptr-1].block;
234 mb[0].dirty = mb[ptr-1].dirty;
235 memcpy (r_buf, r_buf + mb[ptr-1].offset,
236 mb[ptr].offset - mb[ptr-1].offset);
239 mb[1].block = mb[ptr].block;
240 mb[1].dirty = mb[ptr].dirty;
241 mb[1].offset = mb[ptr].offset - mb[ptr-1].offset;
243 r_offset = mb[ptr].offset;
247 border = get_border (is, mb, ptr, cat, firstpos);
255 cmp = (*is->method->compare_item)(i_item, f_item);
256 if (cmp == 0) /* insert i=f */
258 if (!i_mode) /* delete item? */
262 i_more = (*data->read_item)(data->clientData, &i_item_ptr,
264 /* is next input item the same as current except
265 for the delete flag? */
266 cmp = (*is->method->compare_item)(i_item, f_item);
267 if (!cmp && i_mode) /* delete/insert nop? */
269 /* yes! insert as if it was an insert only */
270 memcpy (r_item, i_item, i_item_ptr - i_item);
272 i_more = (*data->read_item)(data->clientData, &i_item_ptr,
277 /* no! delete the item */
285 memcpy (r_item, f_item, f_item_ptr - f_item);
289 i_more = (*data->read_item)(data->clientData, &i_item_ptr,
294 f_more = isc_read_item (pp, &f_item_ptr);
296 else if (cmp > 0) /* insert f */
298 memcpy (r_item, f_item, f_item_ptr - f_item);
301 f_more = isc_read_item (pp, &f_item_ptr);
305 if (!i_mode) /* delete item which isn't there? */
307 logf (LOG_FATAL, "Inconsistent register at offset %d",
311 memcpy (r_item, i_item, i_item_ptr - i_item);
316 i_more = (*data->read_item)(data->clientData, &i_item_ptr,
319 if (r_item) /* insert resulting item? */
321 char *r_out_ptr = r_buf + r_offset;
324 (*is->method->code_item)(ISAMC_ENCODE, r_clientData,
325 &r_out_ptr, &r_item);
326 new_offset = r_out_ptr - r_buf;
330 if (border < new_offset && border >= r_offset)
333 logf (LOG_LOG, "isc: border %d %d", ptr, border);
334 /* Max size of current block category reached ...
335 make new virtual block entry */
338 mb[ptr].offset = r_offset;
339 if (cat == is->max_cat && ptr >= is->method->max_blocks_mem)
341 /* We are dealing with block(s) of max size. Block(s)
342 except one will be flushed. Note: the block(s) are
343 surely not the last one(s).
346 logf (LOG_LOG, "isc: flush B %d sections", ptr-1);
347 flush_blocks (is, mb, ptr-1, r_buf, &firstpos, cat,
349 mb[0].block = mb[ptr-1].block;
350 mb[0].dirty = mb[ptr-1].dirty;
351 memcpy (r_buf, r_buf + mb[ptr-1].offset,
352 mb[ptr].offset - mb[ptr-1].offset);
355 mb[1].block = mb[ptr].block;
356 mb[1].dirty = mb[0].dirty;
357 mb[1].offset = mb[ptr].offset - mb[ptr-1].offset;
358 memcpy (r_buf + mb[1].offset, r_buf + r_offset,
359 new_offset - r_offset);
360 new_offset = (new_offset - r_offset) + mb[1].offset;
363 border = get_border (is, mb, ptr, cat, firstpos);
365 r_offset = new_offset;
367 if (cat < is->max_cat && ptr >= is->method->filecat[cat].mblocks)
369 /* Max number blocks in current category reached ->
370 must switch to next category (with larger block size)
374 (is->files[cat].no_remap)++;
375 /* delete all original block(s) read so far */
376 for (i = 0; i < ptr; i++)
378 isc_release_block (is, pp->cat, mb[i].block);
379 /* also delete all block to be read in the future */
382 /* remap block offsets */
383 assert (mb[j].offset == 0);
387 mb[ptr].offset = r_offset;
388 for (i = 1; i < ptr; i++)
390 int border = is->method->filecat[cat].ifill -
391 ISAMC_BLOCK_OFFSET_1 + mb[j].offset;
393 logf (LOG_LOG, "isc: remap %d border=%d", i, border);
394 if (mb[i+1].offset > border && mb[i].offset <= border)
397 logf (LOG_LOG, "isc: to %d %d", j, mb[i].offset);
400 mb[j].offset = mb[i].offset;
404 logf (LOG_LOG, "isc: remap from %d to %d sections to cat %d",
407 border = get_border (is, mb, ptr, cat, firstpos);
409 logf (LOG_LOG, "isc: border=%d r_offset=%d", border, r_offset);
412 if (mb[ptr].offset < r_offset)
413 { /* make the final boundary offset */
416 mb[ptr].offset = r_offset;
419 { /* empty output. Release last block if any */
420 if (cat == pp->cat && mb[ptr].block)
423 logf (LOG_LOG, "isc: release C");
424 isc_release_block (is, pp->cat, mb[ptr].block);
432 logf (LOG_LOG, "isc: flush C, %d sections", ptr);
436 /* we have to patch initial block with num keys if that
438 if (numKeys != isc_pp_num (pp))
441 logf (LOG_LOG, "isc: patch num keys firstpos=%d num=%d",
443 bf_write (is->files[cat].bf, firstpos, ISAMC_BLOCK_OFFSET_N,
444 sizeof(numKeys), &numKeys);
448 { /* we haven't flushed initial block yet and there surely are some
449 blocks to flush. Make first block dirty if numKeys differ */
450 if (numKeys != isc_pp_num (pp))
453 /* flush rest of block(s) in r_buf */
454 flush_blocks (is, mb, ptr, r_buf, &firstpos, cat, 1, &numKeys);
456 (*is->method->code_stop)(ISAMC_ENCODE, r_clientData);
460 logf (LOG_LOG, "isc: isc_merge return %d %d", cat, firstpos);
462 return cat + firstpos * 8;
465 static char *hexdump(unsigned char *p, int len, char *buff) {
466 static char localbuff[128];
468 if (!buff) buff=localbuff;
471 sprintf(bytebuff,"%02x",*p);
473 strcat(buff,bytebuff);
474 if (len) strcat(buff,",");
480 /* isamh - heikki's append-only isam
481 * Idea: When allocating a new block, allocate memory for a very large block
482 * (maximal blocksize). When done, see if you can shrink it to some
483 * smaller size. First-time indexing will go in optimal blocks, and
484 * following small additions will go to the end of the last of the
485 * maximal ones. Only later, when new blocks need to be allocated, it
486 * may make sense to reserve some extra space...
490 static void isamh_reduceblock(ISAMH is, ISAMH_PP pp, int numKeys)
492 if (pp->is->method->debug > 2)
493 logf(LOG_LOG,"isamh_reduce: block p=%d c=%d o=%d nk=%d ",
494 pp->pos, pp->cat, pp->offset, numKeys);
496 return; /* already allocated in some size */
497 while ( ( pp->cat > 0 ) &&
498 ( pp->offset < is->method->filecat[pp->cat-1].bsize) &&
499 ( numKeys < is->method->filecat[pp->cat-1].mblocks) )
501 pp->pos = isamh_alloc_block(is,pp->cat) ;
502 if (pp->is->method->debug > 2)
503 logf(LOG_LOG,"isamh_reduced block p=%d to c=%d o=%d nk=%d bs=%d",
504 pp->pos, pp->cat, pp->offset, numKeys,
505 is->method->filecat[pp->cat].bsize);
509 ISAMC_P isamh_append (ISAMH is, ISAMH_P ipos, ISAMH_I data)
512 ISAMH_PP pp; /* always the last pp in the chain */
513 ISAMH_PP firstpp; /* always the first one in the chain, may ==pp */
514 ISAMH_PP prevpp; /* the one that points to pp, may be null or ==firstpp */
515 /* needed to postpone the writing of its next field until */
516 /* pp itself has been categorized */
519 int i_more=1, i_mode;
521 char codebuffer[128];
526 void *r_clientData; /* encode client data */
534 pp = firstpp = isamh_pp_open (is, ipos);
535 prevpp =0; /* only used when new blocks allocated */
537 assert (*is->method->code_reset);
539 maxcat=0; /* find the largest block size for default allocation */
540 for ( newcat=0; is->method->filecat[newcat].mblocks > 0; newcat++)
541 if ( is->method->filecat[newcat].bsize >
542 is->method->filecat[maxcat].bsize)
547 pp->cat=maxcat; /* start large... */
548 pp->pos = 0; /* not allocated yet */
549 pp->size= pp->offset = ISAMH_BLOCK_OFFSET_1 ;
550 pp->buf=xrealloc(pp->buf,is->method->filecat[maxcat].bsize);
551 r_clientData = (*is->method->code_start)(ISAMH_ENCODE);
552 if (pp->is->method->debug > 2)
553 logf(LOG_LOG,"isamh_append: starting with new block");
556 { /* existing block */
557 if (isamh_block(firstpp->lastblock) == firstpp->pos)
558 /*!!! TODO: BUG: Compare whole addresses !!! (later) */
559 { /* only one block, we have it already */
560 pp->offset=ISAMH_BLOCK_OFFSET_1;
561 if (pp->is->method->debug > 2)
562 logf(LOG_LOG,"isamh_append: starting with one block %d",pp->pos);
566 if (pp->is->method->debug > 2)
567 logf(LOG_LOG,"isamh_append: starting with multiple blocks %d>%d>%d",
568 firstpp->pos,isamh_block(firstpp->next),isamh_block(firstpp->lastblock));
569 pp=isamh_pp_open(is,firstpp->lastblock);
570 /* dirty, but this can also read a N-block. Just clear extra values*/
572 pp->offset=ISAMH_BLOCK_OFFSET_N;
574 r_clientData = (*is->method->code_start)(ISAMH_ENCODE);
575 if (pp->is->method->debug > 3)
576 logf(LOG_LOG,"isamh_append: scanning to end of block %d %d->%d",
577 pp->pos, pp->offset, pp->size);
579 while (pp->offset<pp->size) {
581 bufptr=pp->buf + pp->offset;
582 (*is->method->code_item)(ISAMH_DECODE, r_clientData, &codeptr, &bufptr);
583 codelen = bufptr - (pp->buf+pp->offset) ;
584 if (pp->is->method->debug > 3)
585 logf(LOG_LOG,"isamh_append: dec at %d %d/%d:%s",
586 pp->offset, codelen, codeptr-codebuffer,
587 hexdump(codebuffer,codeptr-codebuffer,0) );
588 pp->offset += codelen;
590 } /* existing block */
594 i_more = (*data->read_item)(data->clientData,&i_item_ptr,&i_mode);
595 if (pp->is->method->debug > 3)
596 logf(LOG_LOG,"isamh_append 1: m=%d l=%d %s",
597 i_mode, i_item_ptr-i_item, hexdump(i_item,i_item_ptr-i_item,0));
599 maxsize = is->method->filecat[pp->cat].bsize;
603 { /* insert key, ignore all delete keys time being... */
604 codeptr = codebuffer;
606 (*is->method->code_item)(ISAMH_ENCODE, r_clientData, &codeptr, &i_item_ptr);
607 codelen = codeptr-codebuffer;
609 assert( (codelen < 128) && (codelen>0));
611 if (pp->is->method->debug > 3)
612 logf(LOG_LOG,"isamh_append: coded into %d:%s (nk=%d)",
613 codelen,hexdump(codebuffer,codelen,0),firstpp->numKeys);
615 if ( pp->offset + codelen > maxsize )
616 { /* oops, block full, do something */
617 newcat = maxcat; /* start with a large block again */
618 maxkeys = is->method->filecat[pp->cat].mblocks; /* max keys */
619 if (pp->is->method->debug > 2)
620 logf(LOG_LOG,"isamh_append: need new block: %d > %d (k:%d/%d)",
621 pp->offset + codelen, maxsize, firstpp->numKeys,maxkeys );
626 /* Four possibilities: */
628 { /* 1: we have a prevpp that can go on the disk */
629 /* reduce pp, set next ptr, and store block */
630 /* set pp up as new last block, and remember the just */
631 /* filled as (pp) the new prev */
633 isamh_reduceblock(is,pp,firstpp->numKeys);
634 prevpp->next=isamh_addr(pp->pos,pp->cat);
635 isamh_buildlaterblock(prevpp);
636 isamh_write_block(is,prevpp->cat,prevpp->pos,prevpp->buf);
637 if (pp->is->method->debug > 2)
638 logf(LOG_LOG,"isamh_append N1: Wrote prevpp (%d:%d) -> %d:%d",
639 prevpp->pos, prevpp->cat, pp->pos, pp->cat);
640 isamh_pp_close(prevpp); /* it's done its job */
642 pp=isamh_pp_open(is,isamh_addr(0,maxcat)); /* start a large one */
643 pp->size=pp->offset=ISAMH_BLOCK_OFFSET_N ;
647 else if ( (firstpp!=pp) && (firstpp->next != 0))
648 { /* 2: we are working at end of list, but have no prevpp */
649 /* some block (already on disk) points to pp */
650 /* set the newly filled block as prev, don't save yet */
651 /* allocate new pp */
652 if (pp->is->method->debug > 2)
653 logf(LOG_LOG,"isamh_append N2: set up a new prevpp (%d:%d)",
656 pp=isamh_pp_open(is,isamh_addr(0,maxcat)); /* start a large one */
657 pp->size=pp->offset=ISAMH_BLOCK_OFFSET_N ;
661 else if ( (firstpp!=pp) && (firstpp->next==0))
662 { /* 3: we have earlier allocated pp as the second block */
663 /* reduce it to get its address. Set first->next to it */
664 /* move it to prevpp, and create a new pp */
665 isamh_reduceblock(is,pp,firstpp->numKeys);
666 firstpp->next=isamh_addr(pp->pos,pp->cat);
667 if (pp->is->method->debug > 2)
668 logf(LOG_LOG,"isamh_append N3: set up a new firstpp->next (%d:%d)",
671 pp=isamh_pp_open(is,isamh_addr(0,maxcat)); /* start a large one */
672 pp->size=pp->offset=ISAMH_BLOCK_OFFSET_N ;
677 { /* 4: firstpp itself has got full. */
678 /* allocate a new pp for it, store nothing */
680 assert(firstpp->next==0);
681 if (pp->is->method->debug > 2)
682 logf(LOG_LOG,"isamh_append N4: allocated new pp for full first (%d:%d)",
683 firstpp->pos, firstpp->cat);
684 pp=isamh_pp_open(is,isamh_addr(0,maxcat)); /* start a large one */
685 pp->size=pp->offset=ISAMH_BLOCK_OFFSET_N ;
690 maxsize = is->method->filecat[pp->cat].bsize;
691 pp->size=pp->offset=ISAMH_BLOCK_OFFSET_N ;
694 if (pp->is->method->debug > 2)
695 logf(LOG_LOG,"isamh_append: got a new block c=%d p=%d",pp->cat,pp->pos);
698 /* reset the encoding, and code again */
699 (*is->method->code_reset)(r_clientData);
700 codeptr = codebuffer;
702 (*is->method->code_item)(ISAMH_ENCODE, r_clientData, &codeptr, &i_item_ptr);
703 codelen = codeptr-codebuffer;
704 if (pp->is->method->debug > 3)
705 logf(LOG_LOG,"isamh_append: coded again %d:%s (nk=%d)",
706 codelen,hexdump(codebuffer,codelen,0),firstpp->numKeys);
710 /* ok, now we can write it */
711 memcpy(&(pp->buf[pp->offset]), codebuffer, codelen);
712 pp->offset += codelen;
717 /* try to read the next element */
719 i_more = (*data->read_item)(data->clientData,&i_item_ptr,&i_mode);
720 if (pp->is->method->debug > 3)
721 logf(LOG_LOG,"isamh_append 2: m=%d l=%d %s",
722 i_mode, i_item_ptr-i_item, hexdump(i_item,i_item_ptr-i_item,0));
726 isamh_reduceblock(is,pp,firstpp->numKeys);
727 /* may be the same as firstpp! */
730 { /* Write the prev block we have been holding off */
732 prevpp->next = isamh_addr(pp->pos, pp->cat);
733 isamh_buildlaterblock(prevpp);
734 isamh_write_block(is,prevpp->cat,prevpp->pos,prevpp->buf);
735 if (firstpp->next==0) /* can happen if extending many blocks */
736 firstpp->next=isamh_addr(prevpp->pos,prevpp->cat);
737 isamh_pp_close(prevpp);
739 /* Write the last (partial) block, if needed. */
742 pp->next=0; /* just to be sure */
743 if (firstpp->next==0)
744 firstpp->next=isamh_addr(pp->pos,pp->cat);
745 isamh_buildlaterblock(pp);
746 isamh_write_block(is,pp->cat,pp->pos,pp->buf);
749 /* update first block and write it */
750 firstpp->lastblock = isamh_addr(pp->pos,pp->cat);
751 isamh_reduceblock(is,firstpp,firstpp->numKeys);
752 isamh_buildfirstblock(firstpp);
753 isamh_write_block(is,firstpp->cat,firstpp->pos,firstpp->buf);
755 /* release the second block, if we allocated one */
759 /* get return value (before it disappears at close! */
760 retval = isamh_addr(firstpp->pos,firstpp->cat);
762 isamh_pp_close(firstpp);
771 * Revision 1.19 1999-07-14 12:12:07 heikki
772 * Large-block isam-h (may not work too well... Abandoning for isam-d)
774 * Revision 1.17 1999/07/13 14:22:17 heikki
775 * Better allocation strategy in isamh_merge
777 * Revision 1.16 1999/07/08 14:23:27 heikki
778 * Fixed a bug in isamh_pp_read and cleaned up a bit
780 * Revision 1.15 1999/07/07 09:36:04 heikki
781 * Fixed an assertion in isamh
783 * Revision 1.13 1999/07/06 09:37:05 heikki
784 * Working on isamh - not ready yet.
786 * Revision 1.12 1999/06/30 15:03:55 heikki
787 * first take on isamh, the append-only isam structure
789 * Revision 1.11 1999/05/26 07:49:14 adam
792 * Revision 1.10 1998/03/19 12:22:09 adam
795 * Revision 1.9 1998/03/19 10:04:38 adam
798 * Revision 1.8 1998/03/18 09:23:55 adam
799 * Blocks are stored in chunks on free list - up to factor 2 in speed.
800 * Fixed bug that could occur in block category rearrangemen.
802 * Revision 1.7 1998/03/11 11:18:18 adam
803 * Changed the isc_merge to take into account the mfill (minimum-fill).
805 * Revision 1.6 1998/03/06 13:54:03 adam
806 * Fixed two nasty bugs in isc_merge.
808 * Revision 1.5 1997/02/12 20:42:43 adam
809 * Bug fix: during isc_merge operations, some pages weren't marked dirty
810 * even though they should be. At this point the merge operation marks
811 * a page dirty if the previous page changed at all. A better approach is
812 * to mark it dirty if the last key written changed in previous page.
814 * Revision 1.4 1996/11/08 11:15:31 adam
815 * Number of keys in chain are stored in first block and the function
816 * to retrieve this information, isc_pp_num is implemented.
818 * Revision 1.3 1996/11/04 14:08:59 adam
819 * Optimized free block usage.
821 * Revision 1.2 1996/11/01 13:36:46 adam
822 * New element, max_blocks_mem, that control how many blocks of max size
823 * to store in memory during isc_merge.
824 * Function isc_merge now ignores delete/update of identical keys and
825 * the proper blocks are then non-dirty and not written in flush_blocks.
827 * Revision 1.1 1996/11/01 08:59:15 adam
828 * First version of isc_merge that supports update/delete.