* Enclose most operations that update the database in transactions.
* Open all database tables (Db objects) at initialisation time, not every time they are used. This is necessary because tables have to outlive all transactions that refer to them.
This commit is contained in:
Eelco Dolstra
parent
177a7782ae
commit
06d3d7355d
131
src/db.cc
131
src/db.cc
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@ -5,15 +5,6 @@
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/* Wrapper class to ensure proper destruction. */
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class DestroyDb
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{
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Db * db;
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public:
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DestroyDb(Db * _db) : db(_db) { }
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~DestroyDb() { db->close(0); delete db; }
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};
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class DestroyDbc
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{
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Dbc * dbc;
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@ -38,24 +29,39 @@ Transaction::Transaction()
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Transaction::Transaction(Database & db)
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{
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db.requireEnv();
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db.env->txn_begin(0, &txn, 0);
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try {
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db.env->txn_begin(0, &txn, 0);
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} catch (DbException e) { rethrow(e); }
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}
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Transaction::~Transaction()
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{
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if (txn) {
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txn->abort();
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txn = 0;
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}
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if (txn) abort();
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}
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void Transaction::commit()
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{
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if (!txn) throw Error("commit called on null transaction");
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txn->commit(0);
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debug(format("committing transaction %1%") % (void *) txn);
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DbTxn * txn2 = txn;
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txn = 0;
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try {
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txn2->commit(0);
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} catch (DbException e) { rethrow(e); }
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}
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void Transaction::abort()
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{
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if (!txn) throw Error("abort called on null transaction");
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debug(format("aborting transaction %1%") % (void *) txn);
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DbTxn * txn2 = txn;
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txn = 0;
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try {
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txn2->abort();
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} catch (DbException e) { rethrow(e); }
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}
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@ -65,28 +71,18 @@ void Database::requireEnv()
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}
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Db * Database::openDB(const Transaction & txn,
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const string & table, bool create)
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Db * Database::getDb(TableId table)
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{
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requireEnv();
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Db * db = new Db(env, 0);
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try {
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// !!! fixme when switching to BDB 4.1: use txn.
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db->open(table.c_str(), 0,
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DB_HASH, create ? DB_CREATE : 0, 0666);
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} catch (...) {
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delete db;
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throw;
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}
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return db;
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map<TableId, Db *>::iterator i = tables.find(table);
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if (i == tables.end())
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throw Error("unknown table id");
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return i->second;
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}
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Database::Database()
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: env(0)
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, nextId(1)
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{
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}
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@ -95,8 +91,23 @@ Database::~Database()
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{
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if (env) {
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debug(format("closing database environment"));
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env->txn_checkpoint(0, 0, 0);
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env->close(0);
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try {
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for (map<TableId, Db *>::iterator i = tables.begin();
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i != tables.end(); i++)
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{
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debug(format("closing table %1%") % i->first);
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Db * db = i->second;
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db->close(0);
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delete db;
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}
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env->txn_checkpoint(0, 0, 0);
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env->close(0);
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} catch (DbException e) { rethrow(e); }
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delete env;
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}
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}
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@ -112,8 +123,9 @@ void Database::open(const string & path)
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env->set_lg_bsize(32 * 1024); /* default */
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env->set_lg_max(256 * 1024); /* must be > 4 * lg_bsize */
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env->set_lk_detect(DB_LOCK_DEFAULT);
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env->open(path.c_str(),
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env->open(path.c_str(),
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DB_INIT_LOCK | DB_INIT_LOG | DB_INIT_MPOOL | DB_INIT_TXN |
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DB_CREATE,
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0666);
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@ -122,22 +134,36 @@ void Database::open(const string & path)
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}
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void Database::createTable(const string & table)
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TableId Database::openTable(const string & tableName)
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{
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requireEnv();
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TableId table = nextId++;
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try {
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Db * db = openDB(noTxn, table, true);
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DestroyDb destroyDb(db);
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Db * db = new Db(env, 0);
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try {
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// !!! fixme when switching to BDB 4.1: use txn.
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db->open(tableName.c_str(), 0, DB_HASH, DB_CREATE, 0666);
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} catch (...) {
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delete db;
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throw;
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}
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tables[table] = db;
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} catch (DbException e) { rethrow(e); }
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return table;
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}
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bool Database::queryString(const Transaction & txn, const string & table,
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bool Database::queryString(const Transaction & txn, TableId table,
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const string & key, string & data)
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{
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try {
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Db * db = openDB(txn, table, false);
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DestroyDb destroyDb(db);
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Db * db = getDb(table);
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Dbt kt((void *) key.c_str(), key.length());
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Dbt dt;
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@ -156,7 +182,7 @@ bool Database::queryString(const Transaction & txn, const string & table,
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}
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bool Database::queryStrings(const Transaction & txn, const string & table,
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bool Database::queryStrings(const Transaction & txn, TableId table,
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const string & key, Strings & data)
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{
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string d;
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@ -190,13 +216,11 @@ bool Database::queryStrings(const Transaction & txn, const string & table,
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}
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void Database::setString(const Transaction & txn, const string & table,
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void Database::setString(const Transaction & txn, TableId table,
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const string & key, const string & data)
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{
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try {
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Db * db = openDB(txn, table, false);
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DestroyDb destroyDb(db);
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Db * db = getDb(table);
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Dbt kt((void *) key.c_str(), key.length());
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Dbt dt((void *) data.c_str(), data.length());
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db->put(txn.txn, &kt, &dt, 0);
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@ -204,7 +228,7 @@ void Database::setString(const Transaction & txn, const string & table,
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}
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void Database::setStrings(const Transaction & txn, const string & table,
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void Database::setStrings(const Transaction & txn, TableId table,
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const string & key, const Strings & data)
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{
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string d;
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@ -227,28 +251,25 @@ void Database::setStrings(const Transaction & txn, const string & table,
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}
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void Database::delPair(const Transaction & txn, const string & table,
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void Database::delPair(const Transaction & txn, TableId table,
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const string & key)
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{
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try {
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Db * db = openDB(txn, table, false);
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DestroyDb destroyDb(db);
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Db * db = getDb(table);
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Dbt kt((void *) key.c_str(), key.length());
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db->del(txn.txn, &kt, 0);
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} catch (DbException e) { rethrow(e); }
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}
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void Database::enumTable(const Transaction & txn, const string & table,
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void Database::enumTable(const Transaction & txn, TableId table,
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Strings & keys)
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{
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try {
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Db * db = openDB(txn, table, false);
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DestroyDb destroyDb(db);
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Db * db = getDb(table);
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Dbc * dbc;
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db->cursor(0, &dbc, 0);
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db->cursor(txn.txn, &dbc, 0);
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DestroyDbc destroyDbc(dbc);
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Dbt kt, dt;
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25
src/db.hh
25
src/db.hh
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@ -3,6 +3,7 @@
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#include <string>
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#include <list>
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#include <map>
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#include <db_cxx.h>
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@ -26,6 +27,7 @@ public:
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Transaction(Database & _db);
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~Transaction();
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void abort();
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void commit();
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};
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@ -33,6 +35,9 @@ public:
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#define noTxn Transaction()
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typedef unsigned int TableId; /* table handles */
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class Database
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{
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friend class Transaction;
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@ -40,10 +45,12 @@ class Database
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private:
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DbEnv * env;
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TableId nextId;
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map<TableId, Db *> tables;
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void requireEnv();
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Db * openDB(const Transaction & txn,
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const string & table, bool create);
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Db * getDb(TableId table);
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public:
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Database();
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@ -51,24 +58,24 @@ public:
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void open(const string & path);
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void createTable(const string & table);
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TableId openTable(const string & table);
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bool queryString(const Transaction & txn, const string & table,
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bool queryString(const Transaction & txn, TableId table,
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const string & key, string & data);
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bool queryStrings(const Transaction & txn, const string & table,
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bool queryStrings(const Transaction & txn, TableId table,
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const string & key, Strings & data);
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void setString(const Transaction & txn, const string & table,
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void setString(const Transaction & txn, TableId table,
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const string & key, const string & data);
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void setStrings(const Transaction & txn, const string & table,
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void setStrings(const Transaction & txn, TableId table,
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const string & key, const Strings & data);
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void delPair(const Transaction & txn, const string & table,
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void delPair(const Transaction & txn, TableId table,
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const string & key);
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void enumTable(const Transaction & txn, const string & table,
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void enumTable(const Transaction & txn, TableId table,
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Strings & keys);
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};
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@ -5,10 +5,10 @@
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Database nixDB;
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string dbPath2Id = "path2id";
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string dbId2Paths = "id2paths";
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string dbSuccessors = "successors";
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string dbSubstitutes = "substitutes";
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TableId dbPath2Id;
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TableId dbId2Paths;
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TableId dbSuccessors;
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TableId dbSubstitutes;
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string nixStore = "/UNINIT";
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@ -20,13 +20,13 @@ string nixDBPath = "/UNINIT";
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void openDB()
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{
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nixDB.open(nixDBPath);
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dbPath2Id = nixDB.openTable("path2id");
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dbId2Paths = nixDB.openTable("id2paths");
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dbSuccessors = nixDB.openTable("successors");
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dbSubstitutes = nixDB.openTable("substitutes");
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}
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void initDB()
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{
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nixDB.createTable(dbPath2Id);
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nixDB.createTable(dbId2Paths);
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nixDB.createTable(dbSuccessors);
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nixDB.createTable(dbSubstitutes);
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}
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@ -17,13 +17,13 @@ extern Database nixDB;
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Each pair (p, id) records that path $p$ contains an expansion of
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$id$. */
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extern string dbPath2Id;
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extern TableId dbPath2Id;
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/* dbId2Paths :: FSId -> [Path]
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A mapping from ids to lists of paths. */
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extern string dbId2Paths;
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extern TableId dbId2Paths;
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/* dbSuccessors :: FSId -> FSId
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@ -35,7 +35,7 @@ extern string dbId2Paths;
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Note that a term $y$ is successor of $x$ iff there exists a
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sequence of rewrite steps that rewrites $x$ into $y$.
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*/
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extern string dbSuccessors;
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extern TableId dbSuccessors;
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/* dbSubstitutes :: FSId -> [FSId]
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@ -51,7 +51,7 @@ extern string dbSuccessors;
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this case might be an fstate expression that fetches the Nix
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archive.
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*/
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extern string dbSubstitutes;
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extern TableId dbSubstitutes;
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/* Path names. */
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@ -9,7 +9,9 @@
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void registerSuccessor(const FSId & id1, const FSId & id2)
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{
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nixDB.setString(noTxn, dbSuccessors, id1, id2);
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Transaction txn(nixDB);
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nixDB.setString(txn, dbSuccessors, id1, id2);
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txn.commit();
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}
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57
src/store.cc
57
src/store.cc
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@ -32,6 +32,8 @@ struct CopySource : RestoreSource
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void copyPath(string src, string dst)
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{
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debug(format("copying `%1%' to `%2%'") % src % dst);
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/* Unfortunately C++ doesn't support coprocedures, so we have no
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nice way to chain CopySink and CopySource together. Instead we
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fork off a child to run the sink. (Fork-less platforms should
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@ -96,54 +98,69 @@ void registerSubstitute(const FSId & srcId, const FSId & subId)
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/* For now, accept only one substitute per id. */
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Strings subs;
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subs.push_back(subId);
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nixDB.setStrings(noTxn, dbSubstitutes, srcId, subs);
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Transaction txn(nixDB);
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nixDB.setStrings(txn, dbSubstitutes, srcId, subs);
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txn.commit();
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}
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void registerPath(const string & _path, const FSId & id)
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{
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string path(canonPath(_path));
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Transaction txn(nixDB);
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nixDB.setString(noTxn, dbPath2Id, path, id);
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debug(format("registering path `%1%' with id %2%")
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% path % (string) id);
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string oldId;
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if (nixDB.queryString(txn, dbPath2Id, path, oldId)) {
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txn.abort();
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if (id != parseHash(oldId))
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throw Error(format("path `%1%' already contains id %2%")
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% path % oldId);
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return;
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}
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nixDB.setString(txn, dbPath2Id, path, id);
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Strings paths;
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nixDB.queryStrings(noTxn, dbId2Paths, id, paths); /* non-existence = ok */
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for (Strings::iterator it = paths.begin();
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it != paths.end(); it++)
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if (*it == path) return;
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nixDB.queryStrings(txn, dbId2Paths, id, paths); /* non-existence = ok */
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paths.push_back(path);
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nixDB.setStrings(noTxn, dbId2Paths, id, paths);
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nixDB.setStrings(txn, dbId2Paths, id, paths);
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txn.commit();
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}
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void unregisterPath(const string & _path)
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{
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string path(canonPath(_path));
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Transaction txn(nixDB);
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debug(format("unregistering path `%1%'") % path);
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string _id;
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if (!nixDB.queryString(noTxn, dbPath2Id, path, _id)) return;
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if (!nixDB.queryString(txn, dbPath2Id, path, _id)) {
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txn.abort();
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return;
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}
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FSId id(parseHash(_id));
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nixDB.delPair(noTxn, dbPath2Id, path);
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nixDB.delPair(txn, dbPath2Id, path);
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/* begin transaction */
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Strings paths, paths2;
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nixDB.queryStrings(noTxn, dbId2Paths, id, paths); /* non-existence = ok */
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nixDB.queryStrings(txn, dbId2Paths, id, paths); /* non-existence = ok */
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bool changed = false;
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for (Strings::iterator it = paths.begin();
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it != paths.end(); it++)
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if (*it != path) paths2.push_back(*it); else changed = true;
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if (*it != path) paths2.push_back(*it);
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if (changed)
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nixDB.setStrings(noTxn, dbId2Paths, id, paths2);
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/* end transaction */
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nixDB.setStrings(txn, dbId2Paths, id, paths2);
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txn.commit();
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}
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@ -230,6 +247,8 @@ string expandId(const FSId & id, const string & target,
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void addToStore(string srcPath, string & dstPath, FSId & id,
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bool deterministicName)
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{
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debug(format("adding `%1%' to the store") % srcPath);
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srcPath = absPath(srcPath);
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id = hashPath(srcPath);
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