Generate package database statistics on close & make use of it on open

- Turn dbiStat() into more useful: return the number of keys in the
  index, hiding away the BDB internal access method stuff into the backend
- Force statistics gathering at Packages db close, take advantage of
  that when its opened to get a fairly accurate count of packages for
  initial "header verified" bitmap allocation. Previously DB_FAST_STAT
  was used on open but it never returns anything when no stats have
  been previously collected, hence the need for the expensive slow stat.
- The performance hit from stat generation is hardly worth it for
  the bitmap allocation alone, but lets see if there are other uses...
- Also gets rid of dbi_stats member, this is not particularly useful

lib/backend/db3.c

@@ -350,21 +350,27 @@ dbiIndexType dbiType(dbiIndex dbi)
     return dbi->dbi_type;
 }
 
-int dbiStat(dbiIndex dbi, unsigned int flags)
+int dbiNumKeys(dbiIndex dbi, int fast)
 {
     DB * db = dbi->dbi_db;
-    DB_TXN * txnid = NULL;
-    int rc = 0;
+    int rc, nkeys = -1;
+    void *sp = NULL;
 
-    assert(db != NULL);
-    if (flags)
-	flags = DB_FAST_STAT;
-    else
-	flags = 0;
-    dbi->dbi_stats = _free(dbi->dbi_stats);
-    rc = db->stat(db, txnid, &dbi->dbi_stats, flags);
+    rc = db->stat(db, dbi->dbi_txnid, &sp, fast ? DB_FAST_STAT : 0);
     rc = cvtdberr(dbi, "db->stat", rc, _debug);
-    return rc;
+
+    if (rc == 0 && sp) {
+	if (dbi->dbi_dbtype == DB_HASH) {
+	    DB_HASH_STAT *hash = sp;
+	    nkeys = hash->hash_nkeys;
+	} else if (dbi->dbi_dbtype == DB_BTREE) {
+	    DB_BTREE_STAT *btree = sp;
+	    nkeys = btree->bt_nkeys;
+	}
+	free(sp);
+    }
+
+    return nkeys;
 }
 
 int dbiVerify(dbiIndex dbi, unsigned int flags)

lib/backend/dbconfig.c

@@ -119,7 +119,6 @@ static const struct poptOption rdbOptions[] = {
 dbiIndex dbiFree(dbiIndex dbi)
 {
     if (dbi) {
-	dbi->dbi_stats = _free(dbi->dbi_stats);
 	dbi = _free(dbi);
     }
     return dbi;

lib/backend/dbi.h

@@ -49,7 +49,6 @@ struct _dbiIndex {
 
     DB * dbi_db;		/*!< Berkeley DB * handle */
     DB_TXN * dbi_txnid;		/*!< Bekerley DB_TXN * transaction id */
-    void * dbi_stats;		/*!< Berkeley db statistics */
 };
 
 /** \ingroup dbi
@@ -197,13 +196,13 @@ RPM_GNUC_INTERNAL
 int dbiByteSwapped(dbiIndex dbi);
 
 /** \ingroup dbi
- * Is database byte swapped?
+ * Return number of keys in index
  * @param dbi		index database handle
- * @param flags		DB_FAST_STAT or 0
- * @return		0 on success
+ * @param fast		fast, cached estimate or slow but accurate?
+ * @return		number of keys in index, -1 on error
  */
 RPM_GNUC_INTERNAL
-int dbiStat(dbiIndex dbi, unsigned int flags);
+int dbiNumKeys(dbiIndex dbi, int fast);
 
 /** \ingroup dbi
  * Type of dbi (primary data / index)

lib/rpmdb.c

@@ -178,20 +178,15 @@ static dbiIndex rpmdbOpenIndex(rpmdb db, rpmTag rpmtag, unsigned int flags)
 
     if (dbi != NULL && rc == 0) {
 	db->_dbi[dbix] = dbi;
+	/* Grab a fast estimate of package count for allocation */
 	if (rpmtag == RPMDBI_PACKAGES && db->db_bits == NULL) {
-	    db->db_nbits = 1024;
-	    if (!dbiStat(dbi, DB_FAST_STAT)) {
-		DB_HASH_STAT * hash = (DB_HASH_STAT *)dbi->dbi_stats;
-		if (hash)
-		    db->db_nbits += hash->hash_nkeys;
-	    }
+	    int nkeys = dbiNumKeys(dbi, 1);
+	    db->db_nbits = 1024 + (nkeys > 0 ? nkeys : 0);
 	    db->db_bits = PBM_ALLOC(db->db_nbits);
 	}
-    }
-#ifdef HAVE_DB_H
-      else
+    } else {
 	dbi = dbiFree(dbi);
-#endif
+    }
 
 /* FIX: db->_dbi may be NULL */
     return dbi;
@@ -687,6 +682,13 @@ int rpmdbClose(rpmdb db)
 	int xx;
 	if (db->_dbi[dbix] == NULL)
 	    continue;
+
+	/* Force full statistics generation at package db close */
+	if (dbiTags[dbix] == RPMDBI_PACKAGES && 
+		    (db->db_mode & O_ACCMODE) != O_RDONLY) {
+	    (void) dbiNumKeys(db->_dbi[dbix], 0);
+	}
+
     	xx = dbiClose(db->_dbi[dbix], 0);
 	if (xx && rc == 0) rc = xx;
     	db->_dbi[dbix] = NULL;