From e9ed4d75f786e1b592f000cb4a0afb9b16f73cf1 Mon Sep 17 00:00:00 2001 From: Howard Chu Date: Thu, 11 Jul 2013 22:09:47 +0200 Subject: [PATCH] Spill pages, take 3 --- libraries/liblmdb/mdb.c | 368 +++++++++++++++++++++++++++++++++++++-- libraries/liblmdb/midl.c | 4 +- libraries/liblmdb/midl.h | 12 +- 3 files changed, 359 insertions(+), 25 deletions(-) diff --git a/libraries/liblmdb/mdb.c b/libraries/liblmdb/mdb.c index a533ed4..cd99d67 100644 --- a/libraries/liblmdb/mdb.c +++ b/libraries/liblmdb/mdb.c @@ -585,6 +585,7 @@ typedef struct MDB_page { #define P_DIRTY 0x10 /**< dirty page */ #define P_LEAF2 0x20 /**< for #MDB_DUPFIXED records */ #define P_SUBP 0x40 /**< for #MDB_DUPSORT sub-pages */ +#define P_KEEP 0x8000 /**< leave this page alone during spill */ /** @} */ uint16_t mp_flags; /**< @ref mdb_page */ #define mp_lower mp_pb.pb.pb_lower @@ -824,6 +825,10 @@ struct MDB_txn { /** The list of pages that became unused during this transaction. */ MDB_IDL mt_free_pgs; + /** The list of dirty pages we temporarily wrote to disk + * because the dirty list was full. + */ + MDB_IDL mt_spill_pgs; union { MDB_ID2L dirty_list; /**< for write txns: modified pages */ MDB_reader *reader; /**< this thread's reader table slot or NULL */ @@ -857,6 +862,7 @@ struct MDB_txn { #define MDB_TXN_RDONLY 0x01 /**< read-only transaction */ #define MDB_TXN_ERROR 0x02 /**< an error has occurred */ #define MDB_TXN_DIRTY 0x04 /**< must write, even if dirty list is empty */ +#define MDB_TXN_SPILLS 0x08 /**< txn or a parent has spilled pages */ /** @} */ unsigned int mt_flags; /**< @ref mdb_txn */ /** dirty_list maxsize - # of allocated pages allowed, including in parent txns */ @@ -1306,7 +1312,7 @@ mdb_dpage_free(MDB_env *env, MDB_page *dp) } } -/* Return all dirty pages to dpage list */ +/** Return all dirty pages to dpage list */ static void mdb_dlist_free(MDB_txn *txn) { @@ -1320,6 +1326,148 @@ mdb_dlist_free(MDB_txn *txn) dl[0].mid = 0; } +static int mdb_page_flush(MDB_txn *txn); + +/** Spill pages from the dirty list back to disk. + * This is intended to prevent running into #MDB_TXN_FULL situations, + * but note that they may still occur in a few cases: + * 1) pages in #MDB_DUPSORT sub-DBs are never spilled, so if there + * are too many of these dirtied in one txn, the txn may still get + * too full. + * 2) child txns may run out of space if their parents dirtied a + * lot of pages and never spilled them. TODO: we probably should do + * a preemptive spill during #mdb_txn_begin() of a child txn, if + * the parent's dirty_room is below a given threshold. + * 3) our estimate of the txn size could be too small. At the + * moment this seems unlikely. + * + * Otherwise, if not using nested txns, it is expected that apps will + * not run into #MDB_TXN_FULL any more. The pages are flushed to disk + * the same way as for a txn commit, e.g. their P_DIRTY flag is cleared. + * If the txn never references them again, they can be left alone. + * If the txn only reads them, they can be used without any fuss. + * If the txn writes them again, they can be dirtied immediately without + * going thru all of the work of #mdb_page_touch(). Such references are + * handled by #mdb_page_unspill(). + * + * Also note, we never spill DB root pages, nor pages of active cursors, + * because we'll need these back again soon anyway. And in nested txns, + * we can't spill a page in a child txn if it was already spilled in a + * parent txn. That would alter the parent txns' data even though + * the child hasn't committed yet, and we'd have no way to undo it if + * the child aborted. + * + * @param[in] m0 cursor A cursor handle identifying the transaction and + * database for which we are checking space. + * @param[in] key For a put operation, the key being stored. + * @param[in] data For a put operation, the data being stored. + * @return 0 on success, non-zero on failure. + */ +static int +mdb_page_spill(MDB_cursor *m0, MDB_val *key, MDB_val *data) +{ + MDB_txn *txn = m0->mc_txn; + MDB_page *dp; + MDB_ID2L dl = txn->mt_u.dirty_list; + unsigned int i, j; + int rc; + + if (m0->mc_flags & C_SUB) + return MDB_SUCCESS; + + /* Estimate how much space this op will take */ + i = m0->mc_db->md_depth; + /* Named DBs also dirty the main DB */ + if (m0->mc_dbi > MAIN_DBI) + i += txn->mt_dbs[MAIN_DBI].md_depth; + /* For puts, roughly factor in the key+data size */ + if (key) + i += (LEAFSIZE(key, data) + txn->mt_env->me_psize) / txn->mt_env->me_psize; + i += i; /* double it for good measure */ + + if (txn->mt_dirty_room > i) + return MDB_SUCCESS; + + if (!txn->mt_spill_pgs) { + txn->mt_spill_pgs = mdb_midl_alloc(MDB_IDL_UM_MAX); + if (!txn->mt_spill_pgs) + return ENOMEM; + } + + /* Mark all the dirty root pages we want to preserve */ + for (i=0; imt_numdbs; i++) { + if (txn->mt_dbflags[i] & DB_DIRTY) { + j = mdb_mid2l_search(dl, txn->mt_dbs[i].md_root); + if (j <= dl[0].mid) { + dp = dl[j].mptr; + dp->mp_flags |= P_KEEP; + } + } + } + /* Mark all the pages of active cursors we want to preserve */ + for (i=0; imt_numdbs; i++) { + MDB_cursor *mc = txn->mt_cursors[i]; + /* See if m0 is tracked or not */ + if (i == m0->mc_dbi && !(m0->mc_flags & C_UNTRACK)) { + /* nope. tack it on in front */ + m0->mc_next = mc; + mc = m0; + } + for (; mc; mc=mc->mc_next) { + if (mc->mc_flags & C_INITIALIZED) { + for (j=0; jmc_snum; j++) { + if (mc->mc_pg[j]->mp_flags & P_DIRTY) + mc->mc_pg[j]->mp_flags |= P_KEEP; + } + if (txn->mt_dbs[i].md_flags & MDB_DUPSORT) { + MDB_cursor *mx = &mc->mc_xcursor->mx_cursor; + if (mx->mc_flags & C_INITIALIZED) { + for (j=0; jmc_snum; j++) { + if ((mx->mc_pg[j]->mp_flags & (P_SUBP|P_DIRTY)) + == P_DIRTY) + mx->mc_pg[j]->mp_flags |= P_KEEP; + } + } + } + } + } + } + + /* Save the page IDs of all the pages we're flushing */ + for (i=1; i<=dl[0].mid; i++) { + dp = dl[i].mptr; + if (dp->mp_flags & P_KEEP) + continue; + /* Can't spill twice, make sure it's not already in a parent's + * spill list. + */ + if (txn->mt_parent) { + MDB_txn *tx2; + for (tx2 = txn->mt_parent; tx2; tx2 = tx2->mt_parent) { + if (tx2->mt_spill_pgs) { + j = mdb_midl_search(tx2->mt_spill_pgs, dl[i].mid); + if (j <= tx2->mt_spill_pgs[0] && tx2->mt_spill_pgs[j] == dl[i].mid) { + dp->mp_flags |= P_KEEP; + break; + } + } + } + if (tx2) + continue; + } + if ((rc = mdb_midl_append(&txn->mt_spill_pgs, dl[i].mid))) + return rc; + } + mdb_midl_sort(txn->mt_spill_pgs); + + rc = mdb_page_flush(txn); + if (rc == 0) { + txn->mt_dirty_room = MDB_IDL_UM_MAX - dl[0].mid; + txn->mt_flags |= MDB_TXN_SPILLS; + } + return rc; +} + /** Find oldest txnid still referenced. Expects txn->mt_txnid > 0. */ static txnid_t mdb_find_oldest(MDB_txn *txn) @@ -1533,6 +1681,61 @@ mdb_page_copy(MDB_page *dst, MDB_page *src, unsigned int psize) } } +/** Pull a page off the txn's spill list, if present. + * If a page being referenced was spilled to disk in this txn, bring + * it back and make it dirty/writable again. + * @param[in] tx0 the transaction handle. + * @param[in] mp the page being referenced. + * @param[out] ret the writable page, if any. ret is unchanged if + * mp wasn't spilled. + */ +static int +mdb_page_unspill(MDB_txn *tx0, MDB_page *mp, MDB_page **ret) +{ + MDB_env *env = tx0->mt_env; + MDB_txn *txn; + unsigned x; + pgno_t pgno = mp->mp_pgno; + + for (txn = tx0; txn; txn=txn->mt_parent) { + if (!txn->mt_spill_pgs) + continue; + x = mdb_midl_search(txn->mt_spill_pgs, pgno); + if (x <= txn->mt_spill_pgs[0] && txn->mt_spill_pgs[x] == pgno) { + MDB_page *np; + int num; + if (IS_OVERFLOW(mp)) + num = mp->mp_pages; + else + num = 1; + if (env->me_flags & MDB_WRITEMAP) { + np = mp; + } else { + np = mdb_page_malloc(txn, num); + if (!np) + return ENOMEM; + if (num > 1) + memcpy(np, mp, num * env->me_psize); + else + mdb_page_copy(np, mp, env->me_psize); + } + if (txn == tx0) { + /* If in current txn, this page is no longer spilled */ + for (; x < txn->mt_spill_pgs[0]; x++) + txn->mt_spill_pgs[x] = txn->mt_spill_pgs[x+1]; + txn->mt_spill_pgs[0]--; + } /* otherwise, if belonging to a parent txn, the + * page remains spilled until child commits + */ + mdb_page_dirty(tx0, np); + np->mp_flags |= P_DIRTY; + *ret = np; + break; + } + } + return MDB_SUCCESS; +} + /** 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. @@ -1548,6 +1751,14 @@ mdb_page_touch(MDB_cursor *mc) int rc; if (!F_ISSET(mp->mp_flags, P_DIRTY)) { + if (txn->mt_flags & MDB_TXN_SPILLS) { + np = NULL; + rc = mdb_page_unspill(txn, mp, &np); + if (rc) + return rc; + if (np) + goto done; + } if ((rc = mdb_midl_need(&txn->mt_free_pgs, 1)) || (rc = mdb_page_alloc(mc, 1, &np))) return rc; @@ -1595,6 +1806,7 @@ mdb_page_touch(MDB_cursor *mc) np->mp_pgno = pgno; np->mp_flags |= P_DIRTY; +done: /* Adjust cursors pointing to mp */ mc->mc_pg[mc->mc_top] = np; dbi = mc->mc_dbi; @@ -1801,6 +2013,7 @@ mdb_txn_renew0(MDB_txn *txn) txn->mt_u.dirty_list[0].mid = 0; txn->mt_free_pgs = env->me_free_pgs; txn->mt_free_pgs[0] = 0; + txn->mt_spill_pgs = NULL; env->me_txn = txn; } @@ -1906,6 +2119,7 @@ mdb_txn_begin(MDB_env *env, MDB_txn *parent, unsigned int flags, MDB_txn **ret) txn->mt_toggle = parent->mt_toggle; txn->mt_dirty_room = parent->mt_dirty_room; txn->mt_u.dirty_list[0].mid = 0; + txn->mt_spill_pgs = NULL; txn->mt_next_pgno = parent->mt_next_pgno; parent->mt_child = txn; txn->mt_parent = parent; @@ -2008,6 +2222,7 @@ mdb_txn_reset0(MDB_txn *txn, const char *act) txn->mt_parent->mt_child = NULL; env->me_pgstate = ((MDB_ntxn *)txn)->mnt_pgstate; mdb_midl_free(txn->mt_free_pgs); + mdb_midl_free(txn->mt_spill_pgs); free(txn->mt_u.dirty_list); return; } @@ -2210,7 +2425,7 @@ mdb_page_flush(MDB_txn *txn) { MDB_env *env = txn->mt_env; MDB_ID2L dl = txn->mt_u.dirty_list; - unsigned psize = env->me_psize; + unsigned psize = env->me_psize, j; int i, pagecount = dl[0].mid, rc; size_t size = 0, pos = 0; pgno_t pgno = 0; @@ -2224,13 +2439,20 @@ mdb_page_flush(MDB_txn *txn) int n = 0; #endif + j = 0; if (env->me_flags & MDB_WRITEMAP) { /* Clear dirty flags */ for (i = pagecount; i; i--) { dp = dl[i].mptr; + /* Don't flush this page yet */ + if (dp->mp_flags & P_KEEP) { + dp->mp_flags ^= P_KEEP; + dl[++j] = dl[i]; + continue; + } dp->mp_flags &= ~P_DIRTY; } - dl[0].mid = 0; + dl[0].mid = j; return MDB_SUCCESS; } @@ -2238,6 +2460,12 @@ mdb_page_flush(MDB_txn *txn) for (i = 1;; i++) { if (i <= pagecount) { dp = dl[i].mptr; + /* Don't flush this page yet */ + if (dp->mp_flags & P_KEEP) { + dp->mp_flags ^= P_KEEP; + dl[i].mid = 0; + continue; + } pgno = dl[i].mid; /* clear dirty flag */ dp->mp_flags &= ~P_DIRTY; @@ -2309,7 +2537,18 @@ mdb_page_flush(MDB_txn *txn) #endif /* _WIN32 */ } - mdb_dlist_free(txn); + j = 0; + for (i=1; i<=pagecount; i++) { + dp = dl[i].mptr; + /* This is a page we skipped above */ + if (!dl[i].mid) { + dl[++j] = dl[i]; + dl[j].mid = dp->mp_pgno; + continue; + } + mdb_dpage_free(env, dp); + } + dl[0].mid = j; return MDB_SUCCESS; } @@ -2378,6 +2617,37 @@ mdb_txn_commit(MDB_txn *txn) dst = parent->mt_u.dirty_list; src = txn->mt_u.dirty_list; + /* Remove anything in our dirty list from parent's spill list */ + if (parent->mt_spill_pgs) { + x = parent->mt_spill_pgs[0]; + len = x; + /* zero out our dirty pages in parent spill list */ + for (i=1; i<=src[0].mid; i++) { + if (src[i].mid < parent->mt_spill_pgs[x]) + continue; + if (src[i].mid > parent->mt_spill_pgs[x]) { + if (x <= 1) + break; + x--; + continue; + } + parent->mt_spill_pgs[x] = 0; + len--; + } + /* OK, we had a few hits, squash zeros from the spill list */ + if (len < parent->mt_spill_pgs[0]) { + x=1; + for (y=1; y<=parent->mt_spill_pgs[0]; y++) { + if (parent->mt_spill_pgs[y]) { + if (y != x) { + parent->mt_spill_pgs[x] = parent->mt_spill_pgs[y]; + } + x++; + } + } + parent->mt_spill_pgs[0] = len; + } + } /* Find len = length of merging our dirty list with parent's */ x = dst[0].mid; dst[0].mid = 0; /* simplify loops */ @@ -2409,6 +2679,15 @@ mdb_txn_commit(MDB_txn *txn) dst[0].mid = len; free(txn->mt_u.dirty_list); parent->mt_dirty_room = txn->mt_dirty_room; + if (txn->mt_spill_pgs) { + if (parent->mt_spill_pgs) { + mdb_midl_append_list(&parent->mt_spill_pgs, txn->mt_spill_pgs); + mdb_midl_free(txn->mt_spill_pgs); + mdb_midl_sort(parent->mt_spill_pgs); + } else { + parent->mt_spill_pgs = txn->mt_spill_pgs; + } + } parent->mt_child = NULL; mdb_midl_free(((MDB_ntxn *)txn)->mnt_pgstate.mf_pghead); @@ -3991,6 +4270,19 @@ mdb_page_get(MDB_txn *txn, pgno_t pgno, MDB_page **ret, int *lvl) level = 1; do { MDB_ID2L dl = tx2->mt_u.dirty_list; + unsigned x; + /* Spilled pages were dirtied in this txn and flushed + * because the dirty list got full. Bring this page + * back in from the map (but don't unspill it here, + * leave that unless page_touch happens again). + */ + if (tx2->mt_spill_pgs) { + x = mdb_midl_search(tx2->mt_spill_pgs, pgno); + if (x <= tx2->mt_spill_pgs[0] && tx2->mt_spill_pgs[x] == pgno) { + p = (MDB_page *)(txn->mt_env->me_map + txn->mt_env->me_psize * pgno); + goto done; + } + } if (dl[0].mid) { unsigned x = mdb_mid2l_search(dl, pgno); if (x <= dl[0].mid && dl[x].mid == pgno) { @@ -4091,6 +4383,8 @@ mdb_page_search_root(MDB_cursor *mc, MDB_val *key, int modify) DPRINTF("found leaf page %zu for key [%s]", mp->mp_pgno, key ? DKEY(key) : NULL); + mc->mc_flags |= C_INITIALIZED; + mc->mc_flags &= ~C_EOF; return MDB_SUCCESS; } @@ -4218,11 +4512,21 @@ mdb_ovpage_free(MDB_cursor *mc, MDB_page *mp) int rc; DPRINTF("free ov page %zu (%d)", pg, ovpages); - /* If the page is dirty we just acquired it, so we should - * give it back to our current free list, if any. + /* If the page is dirty or on the spill list we just acquired it, + * so we should give it back to our current free list, if any. * Not currently supported in nested txns. * Otherwise put it onto the list of pages we freed in this txn. */ + if (!(mp->mp_flags & P_DIRTY) && txn->mt_spill_pgs) { + unsigned x = mdb_midl_search(txn->mt_spill_pgs, pg); + if (x <= txn->mt_spill_pgs[0] && txn->mt_spill_pgs[x] == pg) { + /* This page is no longer spilled */ + for (; x < txn->mt_spill_pgs[0]; x++) + txn->mt_spill_pgs[x] = txn->mt_spill_pgs[x+1]; + txn->mt_spill_pgs[0]--; + goto release; + } + } if ((mp->mp_flags & P_DIRTY) && !txn->mt_parent && env->me_pghead) { unsigned j, x; pgno_t *mop; @@ -4248,6 +4552,7 @@ mdb_ovpage_free(MDB_cursor *mc, MDB_page *mp) } if (!(env->me_flags & MDB_WRITEMAP)) mdb_dpage_free(env, mp); +release: /* Insert in me_pghead */ mop = env->me_pghead; j = mop[0] + ovpages; @@ -4964,6 +5269,9 @@ mdb_cursor_touch(MDB_cursor *mc) return MDB_SUCCESS; } +/** Do not spill pages to disk if txn is getting full, may fail instead */ +#define MDB_NOSPILL 0x8000 + int mdb_cursor_put(MDB_cursor *mc, MDB_val *key, MDB_val *data, unsigned int flags) @@ -4974,7 +5282,7 @@ mdb_cursor_put(MDB_cursor *mc, MDB_val *key, MDB_val *data, MDB_page *fp; MDB_db dummy; int do_sub = 0, insert = 0; - unsigned int mcount = 0, dcount = 0; + unsigned int mcount = 0, dcount = 0, nospill; size_t nsize; int rc, rc2; MDB_pagebuf pbuf; @@ -4992,6 +5300,9 @@ mdb_cursor_put(MDB_cursor *mc, MDB_val *key, MDB_val *data, return EINVAL; } + nospill = flags & MDB_NOSPILL; + flags &= ~MDB_NOSPILL; + if (F_ISSET(mc->mc_txn->mt_flags, MDB_TXN_RDONLY)) return EACCES; @@ -5048,7 +5359,17 @@ mdb_cursor_put(MDB_cursor *mc, MDB_val *key, MDB_val *data, return rc; } - /* Cursor is positioned */ + /* Cursor is positioned, check for room in the dirty list */ + if (!nospill) { + if (flags & MDB_MULTIPLE) { + rdata = &xdata; + xdata.mv_size = data->mv_size * dcount; + } else { + rdata = data; + } + if ((rc2 = mdb_page_spill(mc, key, rdata))) + return rc2; + } if (rc == MDB_NO_ROOT) { MDB_page *np; @@ -5227,8 +5548,18 @@ current: return rc2; ovpages = omp->mp_pages; - /* Is the ov page writable and large enough? */ - if ((omp->mp_flags & P_DIRTY) && ovpages >= dpages) { + /* Is the ov page large enough? */ + if (ovpages >= dpages) { + if (!(omp->mp_flags & P_DIRTY) && + (level || (mc->mc_txn->mt_env->me_flags & MDB_WRITEMAP))) + { + rc = mdb_page_unspill(mc->mc_txn, omp, &omp); + if (rc) + return rc; + level = 0; /* dirty in this txn or clean */ + } + /* Is it dirty? */ + if (omp->mp_flags & P_DIRTY) { /* yes, overwrite it. Note in this case we don't * bother to try shrinking the page if the new data * is smaller than the overflow threshold. @@ -5261,10 +5592,10 @@ current: else memcpy(METADATA(omp), data->mv_data, data->mv_size); goto done; - } else { - if ((rc2 = mdb_ovpage_free(mc, omp)) != MDB_SUCCESS) - return rc2; + } } + if ((rc2 = mdb_ovpage_free(mc, omp)) != MDB_SUCCESS) + return rc2; } else if (NODEDSZ(leaf) == data->mv_size) { /* same size, just replace it. Note that we could * also reuse this node if the new data is smaller, @@ -5337,10 +5668,11 @@ put_sub: xdata.mv_data = ""; leaf = NODEPTR(mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top]); if (flags & MDB_CURRENT) { - xflags = MDB_CURRENT; + xflags = MDB_CURRENT|MDB_NOSPILL; } else { mdb_xcursor_init1(mc, leaf); - xflags = (flags & MDB_NODUPDATA) ? MDB_NOOVERWRITE : 0; + xflags = (flags & MDB_NODUPDATA) ? + MDB_NOOVERWRITE|MDB_NOSPILL : MDB_NOSPILL; } /* converted, write the original data first */ if (dkey.mv_size) { @@ -5411,6 +5743,10 @@ mdb_cursor_del(MDB_cursor *mc, unsigned int flags) if (!(mc->mc_flags & C_INITIALIZED)) return EINVAL; + if (!(flags & MDB_NOSPILL) && (rc = mdb_page_spill(mc, NULL, NULL))) + return rc; + flags &= ~MDB_NOSPILL; /* TODO: Or change (flags != MDB_NODUPDATA) to ~(flags & MDB_NODUPDATA), not looking at the logic of that code just now */ + rc = mdb_cursor_touch(mc); if (rc) return rc; @@ -5422,7 +5758,7 @@ mdb_cursor_del(MDB_cursor *mc, unsigned int flags) if (!F_ISSET(leaf->mn_flags, F_SUBDATA)) { mc->mc_xcursor->mx_cursor.mc_pg[0] = NODEDATA(leaf); } - rc = mdb_cursor_del(&mc->mc_xcursor->mx_cursor, 0); + rc = mdb_cursor_del(&mc->mc_xcursor->mx_cursor, MDB_NOSPILL); /* If sub-DB still has entries, we're done */ if (mc->mc_xcursor->mx_db.md_entries) { if (leaf->mn_flags & F_SUBDATA) { diff --git a/libraries/liblmdb/midl.c b/libraries/liblmdb/midl.c index e7bd680..86e4592 100644 --- a/libraries/liblmdb/midl.c +++ b/libraries/liblmdb/midl.c @@ -31,8 +31,7 @@ */ #define CMP(x,y) ( (x) < (y) ? -1 : (x) > (y) ) -#if 0 /* superseded by append/sort */ -static unsigned mdb_midl_search( MDB_IDL ids, MDB_ID id ) +unsigned mdb_midl_search( MDB_IDL ids, MDB_ID id ) { /* * binary search of id in ids @@ -67,6 +66,7 @@ static unsigned mdb_midl_search( MDB_IDL ids, MDB_ID id ) return cursor; } +#if 0 /* superseded by append/sort */ int mdb_midl_insert( MDB_IDL ids, MDB_ID id ) { unsigned x, i; diff --git a/libraries/liblmdb/midl.h b/libraries/liblmdb/midl.h index 9ce7133..b0bdff3 100644 --- a/libraries/liblmdb/midl.h +++ b/libraries/liblmdb/midl.h @@ -74,14 +74,12 @@ typedef MDB_ID *MDB_IDL; xidl[xlen] = (id); \ } while (0) -#if 0 /* superseded by append/sort */ - /** Insert an ID into an IDL. - * @param[in,out] ids The IDL to insert into. - * @param[in] id The ID to insert. - * @return 0 on success, -1 if ID was already present, -2 on error. + /** Search for an ID in an IDL. + * @param[in] ids The IDL to search. + * @param[in] id The ID to search for. + * @return The index of the first ID greater than or equal to \b id. */ -int mdb_midl_insert( MDB_IDL ids, MDB_ID id ); -#endif +unsigned mdb_midl_search( MDB_IDL ids, MDB_ID id ); /** Allocate an IDL. * Allocates memory for an IDL of the given size.