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Write optimization: avoid copying unused portions of pages.

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This commit is contained in:
Howard Chu 2012-07-31 16:03:48 -07:00
parent 234cd9dfb5
commit d1120fbccc
1 changed files with 30 additions and 4 deletions
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30
libraries/libmdb/mdb.c
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@ -1328,6 +1328,27 @@ none:
return np;
}
/** Copy a page: avoid copying unused portions of the page.
* @param[in] dst page to copy into
* @param[in] src page to copy from
*/
static void
mdb_page_copy(MDB_page *dst, MDB_page *src, unsigned int psize)
{
dst->mp_flags = src->mp_flags | P_DIRTY;
dst->mp_pages = src->mp_pages;
if (IS_LEAF2(src)) {
memcpy(dst->mp_ptrs, src->mp_ptrs, psize - PAGEHDRSZ - SIZELEFT(src));
} else {
unsigned int i, nkeys = NUMKEYS(src);
for (i=0; i<nkeys; i++)
dst->mp_ptrs[i] = src->mp_ptrs[i];
memcpy((char *)dst+src->mp_upper, (char *)src+src->mp_upper,
psize - src->mp_upper);
}
}
/** Touch a page: make it dirty and re-insert into tree with updated pgno.
* @param[in] mc cursor pointing to the page to be touched
* @return 0 on success, non-zero on failure.
@ -1345,11 +1366,16 @@ mdb_page_touch(MDB_cursor *mc)
DPRINTF("touched db %u page %zu -> %zu", mc->mc_dbi, mp->mp_pgno, np->mp_pgno);
assert(mp->mp_pgno != np->mp_pgno);
mdb_midl_append(&mc->mc_txn->mt_free_pgs, mp->mp_pgno);
if (SIZELEFT(mp)) {
/* If page isn't full, just copy the used portion */
mdb_page_copy(np, mp, mc->mc_txn->mt_env->me_psize);
} else {
pgno = np->mp_pgno;
memcpy(np, mp, mc->mc_txn->mt_env->me_psize);
np->mp_pgno = pgno;
np->mp_flags |= P_DIRTY;
}
mp = np;
mp->mp_pgno = pgno;
mp->mp_flags |= P_DIRTY;
finish:
/* Adjust other cursors pointing to mp */