+/*
+ * This file is part of DisOrder
+ * Copyright (C) 2009 Richard Kettlewell
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+/** @file server/dbparams.c
+ * @brief Parameters affecting the database
+ *
+ * Rescan can regenerate aliases and the search and tag databases but
+ * we rather assume that they are either empty or good. Therefore we
+ * need to store anything that can affect these values and erase them
+ * if they change.
+ *
+ * The solution is a global pref _dbparams which contains the hash of
+ * the alias, stopword and namepart data.
+ */
+#include "disorder-server.h"
+#include <gcrypt.h>
+
+static int dbparams_cleanup(DB_TXN *tid);
+static void h_write_string(gcrypt_hash_handle h,
+ const char *s);
+static char *compute_dbparams(void);
+
+/** @brief Check whether database parameters have changed
+ *
+ * If the database parameters have changed then deletes the search and
+ * tag database contents and all aliases. The subsequent rescan will
+ * regenerate them.
+ */
+void dbparams_check(void) {
+ const char *newparams = compute_dbparams();
+ const char *oldparams = trackdb_get_global("_dbparams");
+
+ // If the parameters match, return straight away
+ if(oldparams && !strcmp(newparams, oldparams))
+ return;
+ // Log what we're going to do
+ for(;;) {
+ DB_TXN *tid;
+ if(oldparams)
+ info("database parameter string changed from %s to %s - removing old data",
+ oldparams, newparams);
+ else {
+ info("new database parameter string %s - removing old data",
+ newparams);
+ /* This is a slightly annoying case; the global pref wasn't present. In
+ * practice this is almost certainly either an upgrade (with no change to
+ * any relevant parameters) or a new installation (with no tracks).
+ *
+ * The new installation case doesn't matter much; clearing an empty
+ * search database and iterating over a likewise track database won't
+ * take long.
+ *
+ * However for upgrade this will throw away a lot of data and laboriously
+ * regenerate it, which is rather a shame.
+ */
+ }
+ tid = trackdb_begin_transaction();
+ int err = dbparams_cleanup(tid);
+ if(!err)
+ err = trackdb_set_global_tid("_dbparams", newparams, tid);
+ switch(err) {
+ case 0:
+ trackdb_commit_transaction(tid);
+ info("removed old data OK, will regenerate on rescan");
+ return;
+ case DB_LOCK_DEADLOCK:
+ /* Deadlocked, try again */
+ trackdb_abort_transaction(tid);
+ break;
+ default:
+ fatal(0, "error updating database: %s", db_strerror(err));
+ }
+ }
+}
+
+/** @brief Clean up databases */
+static int dbparams_cleanup(DB_TXN *tid) {
+ int err;
+ u_int32_t count;
+
+ /* We'll regenerate search.db based on the new set of stopwords */
+ if((err = trackdb_searchdb->truncate(trackdb_searchdb, tid, &count, 0))) {
+ error(err, "truncating search.db: %s", db_strerror(err));
+ return err;
+ }
+ /* We'll regenerate aliases based on the new alias/namepart settings, so
+ * delete all the alias records currently present
+ *
+ * TODO this looks suspiciously similar to part of dump.c
+ */
+ DBC *cursor;
+ DBT k, d;
+ cursor = trackdb_opencursor(trackdb_tracksdb, tid);
+ if((err = cursor->c_get(cursor, prepare_data(&k), prepare_data(&d),
+ DB_FIRST)) == DB_LOCK_DEADLOCK) {
+ error(0, "cursor->c_get: %s", db_strerror(err));
+ goto done;
+ }
+ while(err == 0) {
+ struct kvp *data = kvp_urldecode(d.data, d.size);
+ if(kvp_get(data, "_alias_for")) {
+ if((err = cursor->c_del(cursor, 0))) {
+ error(0, "cursor->c_del: %s", db_strerror(err));
+ goto done;
+ }
+ }
+ err = cursor->c_get(cursor, prepare_data(&k), prepare_data(&d), DB_NEXT);
+ }
+ if(err == DB_LOCK_DEADLOCK) {
+ error(0, "cursor operation: %s", db_strerror(err));
+ goto done;
+ }
+ if(err != DB_NOTFOUND)
+ fatal(0, "cursor->c_get: %s", db_strerror(err));
+ err = 0;
+done:
+ if(trackdb_closecursor(cursor) && !err) err = DB_LOCK_DEADLOCK;
+ return err;
+}
+
+/** @brief Write a string into a gcrypt hash function
+ * @param h Hash handle
+ * @param s String to write
+ *
+ * The 0 terminator is included in the byte written.
+ */
+static void h_write_string(gcrypt_hash_handle h,
+ const char *s) {
+ gcry_md_write(h, s, strlen(s) + 1);
+}
+
+/** @brief Compute database parameters hash
+ * @return Opaque string encapsulating database parameters
+ */
+static char *compute_dbparams(void) {
+ gcry_error_t e;
+ gcrypt_hash_handle h;
+
+ if((e = gcry_md_open(&h, GCRY_MD_SHA256, 0)))
+ fatal(0, "gcry_md_open: %s", gcry_strerror(e));
+ h_write_string(h, "alias");
+ h_write_string(h, config->alias);
+ for(int n = 0; n < config->stopword.n; ++n) {
+ h_write_string(h, "stopword");
+ h_write_string(h, config->stopword.s[n]);
+ }
+ for(int n = 0; n < config->namepart.n; ++n) {
+ h_write_string(h, "namepart");
+ h_write_string(h, config->namepart.s[n].part);
+ h_write_string(h, config->namepart.s[n].res);
+ h_write_string(h, config->namepart.s[n].replace);
+ h_write_string(h, config->namepart.s[n].context);
+ char buffer[64];
+ snprintf(buffer, sizeof buffer, "%u", config->namepart.s[n].reflags);
+ h_write_string(h, buffer);
+ }
+ char *result;
+ byte_xasprintf(&result, "dbparams-0-sha256:%s",
+ hex(gcry_md_read(h, GCRY_MD_SHA256),
+ gcry_md_get_algo_dlen(GCRY_MD_SHA256)));
+ gcry_md_close(h);
+ return result;
+}
+
+/*
+Local Variables:
+c-basic-offset:2
+comment-column:40
+fill-column:79
+indent-tabs-mode:nil
+End:
+*/
~mdw / disorder / commitdiff