90d6f8bf62
libglim is an Apache-licensed C++ wrapper for lmdb, and rather than rolling our own it seems prudent to use it. Note: lmdb is not included in it, and unless something happens as did with libunbound, should be installed via each OS' package manager or equivalent.
539 lines
19 KiB
C++
539 lines
19 KiB
C++
#ifndef GLIM_SQLITE_HPP_
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#define GLIM_SQLITE_HPP_
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/**
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* A threaded interface to <a href="http://sqlite.org/">SQLite</a>.
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* This file is a header-only library,
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* whose sole dependencies should be standard STL and posix threading libraries.
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* You can extract this file out of the "glim" library to include it separately in your project.
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* @code
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Copyright 2006-2012 Kozarezov Artem Aleksandrovich
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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* @endcode
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* @file
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*/
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#include <stdexcept>
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#include <string>
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#include <sqlite3.h>
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#include <pthread.h>
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#include <string.h> // strerror
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#include <sys/types.h> // stat
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#include <sys/stat.h> // stat
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#include <unistd.h> // stat
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#include <errno.h> // stat
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#include <stdio.h> // snprintf
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#include <stdint.h>
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namespace glim {
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class SqliteSession;
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class SqliteQuery;
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struct SqliteEx: public std::runtime_error {
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SqliteEx (const std::string& what): std::runtime_error (what) {}
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};
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/**
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* The database.
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* According to sqlite3_open <a href="http://sqlite.org/capi3ref.html#sqlite3_open">documentation</a>,
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* only the thread that opened the database can safely access it. This restriction was
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* relaxed, as described in the <a href="http://www.sqlite.org/faq.html#q8">FAQ</a>
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* (the "Is SQLite threadsafe?" question), so we can use the library from multiple
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* threads, but only if no more than one thread at a time accesses the database.
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* This restriction is, in fact, beneficial if the database is used from a single application:
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* by restricting access to a sigle thread at a time, we effectively avoid all deadlock issues.\n
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* This library goals are:\n
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* \li to ensure that SQLite is used in a thread-safe way,
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* \li to provide additional threaded quirks, such as delayed updates (not implemented).
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*
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* The library is targeted at SQLite setup which is \b not \c -DTHREADSAFE,
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* since this is the default setup on UNIX architectures.\n
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* \n
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* This file is a header-only library,
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* whose sole dependencies should be standard STL and posix threading libraries.
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* You can extract this file out of the "glim" library to include it separately in your project.\n
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* \n
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* This library is targeted at UTF-8 API. There is no plans to support the UTF-16 API.\n
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* \n
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* See also:\n
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* \li http://www.sqlite.org/cvstrac/fileview?f=sqlite/src/server.c\n
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* for another way of handling multithreading with SQLite.
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*/
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class Sqlite {
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/// No copying allowed.
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Sqlite& operator = (const Sqlite& other) {return *this;}
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/// No copying allowed.
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Sqlite (const Sqlite& other) = delete;
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friend class SqliteSession;
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protected:
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/// Filename the database was opened with; we need it to reopen the database on fork()s.
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/// std::string is used to avoid memory allocation issues.
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std::string filename;
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::sqlite3* handler;
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::pthread_mutex_t mutex;
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public:
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/// Flags for the Sqlite constructor.
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enum Flags {
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/**
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* The file will be checked for existence.
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* SqliteEx is thrown if the file is not accessible;
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* format of the error description is "$filename: $strerror".\n
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* Usage example: \code Sqlite db ("filename", Sqlite::existing); \endcode
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*/
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existing = 1
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};
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/**
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* Opens the database.
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* @param filename Database filename (UTF-8).
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* @param flags Optional. Currently there is the #existing flag.
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* @throws SqliteEx Thrown if we can't open the database.
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*/
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Sqlite (std::string filename, int flags = 0) {
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if (flags & existing) {
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// Check if the file exists already.
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struct stat st; if (stat (filename.c_str(), &st))
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throw SqliteEx (filename + ": " + ::strerror(errno));
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}
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::pthread_mutex_init (&mutex, NULL);
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this->filename = filename;
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if (::sqlite3_open(filename.c_str(), &handler) != SQLITE_OK)
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throw SqliteEx (std::string("sqlite3_open(") + filename + "): " + ::sqlite3_errmsg(handler));
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}
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/**
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* Closes the database.
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* @throws SqliteEx Thrown if we can't close the database.
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*/
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~Sqlite () {
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::pthread_mutex_destroy (&mutex);
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if (::sqlite3_close(handler) != SQLITE_OK)
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throw SqliteEx (std::string ("sqlite3_close(): ") + ::sqlite3_errmsg(handler));
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}
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Sqlite& exec (const char* query);
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/**
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* Invokes `exec` on `query.c_str()`.
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* Example:\code
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* glim::Sqlite sqlite (":memory:");
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* for (std::string pv: {"page_size = 4096", "secure_delete = 1"}) sqlite->exec2 ("PRAGMA " + pv); \endcode
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*/
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template <typename StringLike> Sqlite& exec2 (StringLike query) {return exec (query.c_str());}
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};
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/**
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* A single thread session with Sqlite.
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* Only a sigle thread at a time can have an SqliteSession,
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* all other threads will wait, in the SqliteSession constructor,
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* till the active session is either closed or destructed.
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*/
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class SqliteSession {
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/// No copying allowed.
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SqliteSession& operator = (const SqliteSession& other) {return *this;}
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/// No copying allowed.
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SqliteSession(SqliteSession& other): db (NULL) {}
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protected:
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Sqlite* db;
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public:
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/**
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* Locks the database.
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* @throws SqliteEx if a mutex error occurs.
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*/
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SqliteSession (Sqlite* sqlite): db (sqlite) {
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int err = ::pthread_mutex_lock (&(db->mutex));
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if (err != 0) throw SqliteEx (std::string ("error locking the mutex: ") + ::strerror(err));
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}
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/**
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* A shorter way to construct query from the session.
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* Usage example: \code ses.query(S("create table test (i integer)")).step() \endcode
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* @see SqliteQuery#qstep
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*/
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template <typename T>
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SqliteQuery query (T t);
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/// Automatically unlocks the database.
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/// @see close
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~SqliteSession () {close();}
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/**
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* Unlock the database.
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* It is safe to call this method multiple times.\n
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* You must not use the session after it was closed.\n
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* All resources allocated within this session must be released before the session is closed.
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* @throws SqliteEx if a mutex error occurs.
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*/
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void close () {
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if (db == NULL) return;
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int err = ::pthread_mutex_unlock (&(db->mutex));
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db = NULL;
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if (err != 0) throw SqliteEx (std::string ("error unlocking the mutex: ") + ::strerror(err));
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}
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/// True if the \c close method has been already called on this SqliteSession.
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bool isClosed () const {
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return db == NULL;
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}
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/**
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* This class can be used in place of the SQLite handler.
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* Make sure you've released any resources thus manually acquired before this SqliteSession is closed.
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* Usage example:
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* @code
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* glim::Sqlite db (":memory:");
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* glim::SqliteSession ses (&db);
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* sqlite3_exec (ses, "PRAGMA page_size = 4096;", NULL, NULL, NULL);
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* @endcode
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*/
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operator ::sqlite3* () const {return db->handler;}
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};
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/**
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* Execute the given query, throwing SqliteEx on failure.\n
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* Example:\code
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* glim::Sqlite sqlite (":memory:");
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* sqlite.exec ("PRAGMA page_size = 4096") .exec ("PRAGMA secure_delete = 1"); \endcode
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*/
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inline Sqlite& Sqlite::exec (const char* query) {
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SqliteSession ses (this); // Maintains the locks.
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char* errmsg = NULL; ::sqlite3_exec (handler, query, NULL, NULL, &errmsg);
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if (errmsg) throw SqliteEx (std::string ("Sqlite::exec, error in query (") + query + "): " + errmsg);
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return *this;
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}
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/**
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* Wraps the sqlite3_stmt; will prepare it, bind values, query and finalize.
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*/
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class SqliteQuery {
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protected:
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::sqlite3_stmt* statement;
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SqliteSession* session;
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int bindCounter;
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/// -1 if statement isn't DONE.
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int mChanges;
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void prepare (SqliteSession* session, char const* query, int queryLength) {
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::sqlite3* handler = *session;
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if (::sqlite3_prepare_v2 (handler, query, queryLength, &statement, NULL) != SQLITE_OK)
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throw SqliteEx (std::string(query, queryLength) + ": " + ::sqlite3_errmsg(handler));
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}
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/** Shan't copy. */
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SqliteQuery (const SqliteQuery& other) = delete;
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public:
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SqliteQuery (SqliteQuery&& rvalue) {
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statement = rvalue.statement;
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session = rvalue.session;
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bindCounter = rvalue.bindCounter;
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mChanges = rvalue.mChanges;
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rvalue.statement = nullptr;
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}
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/**
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* Prepares the query.
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* @throws SqliteEx if sqlite3_prepare fails; format of the error message is "$query: $errmsg".
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*/
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SqliteQuery (SqliteSession* session, char const* query, int queryLength)
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: statement (NULL), session (session), bindCounter (0), mChanges (-1) {
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prepare (session, query, queryLength);
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}
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/**
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* Prepares the query.
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* @throws SqliteEx if sqlite3_prepare fails; format of the error message is "$query: $errmsg".
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*/
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SqliteQuery (SqliteSession* session, std::pair<char const*, int> query)
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: statement (NULL), session (session), bindCounter (0), mChanges (-1) {
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prepare (session, query.first, query.second);
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}
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/**
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* Prepares the query.
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* @throws SqliteEx if sqlite3_prepare fails; format of the error message is "$query: $errmsg".
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*/
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SqliteQuery (SqliteSession* session, std::string query)
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: statement (NULL), session (session), bindCounter (0), mChanges (-1) {
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prepare (session, query.c_str(), query.length());
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}
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/**
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* Release resources.
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* @see http://sqlite.org/capi3ref.html#sqlite3_finalize
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*/
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~SqliteQuery () {
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if (statement) ::sqlite3_finalize (statement);
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}
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/// Call this (followed by the #step) if you need the query to be re-executed.
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/// @see http://sqlite.org/capi3ref.html#sqlite3_reset
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SqliteQuery& reset () {
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bindCounter = 0;
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mChanges = -1;
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::sqlite3_reset (statement);
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return *this;
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}
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/// Synonym for #step.
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bool next () {return step();}
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/**
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* Invokes sqlite3_step.
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* @return \c true if there was a row fetched successfully, \c false if there is no more rows.
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* @see http://sqlite.org/capi3ref.html#sqlite3_step
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*/
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bool step () {
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if (mChanges >= 0) {mChanges = 0; return false;}
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int ret = ::sqlite3_step (statement);
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if (ret == SQLITE_ROW) return true;
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if (ret == SQLITE_DONE) {
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mChanges = ::sqlite3_changes (*session);
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return false;
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}
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throw SqliteEx (std::string(::sqlite3_errmsg(*session)));
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}
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/**
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* Perform #step and throw an exception if #step has returned \c false.
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* Usage example:
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* \code (ses.query(S("select count(*) from test where idx = ?")) << 12345).qstep().intAt(1) \endcode
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*/
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SqliteQuery& qstep () {
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if (!step())
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throw SqliteEx (std::string("qstep: no rows returned / affected"));
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return *this;
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}
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/**
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* Invokes a DML query and returns the number of rows affected.
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* Example: \code
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* int affected = (ses.query(S("update test set count = count + ? where id = ?")) << 1 << 9).ustep();
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* \endcode
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* @see http://sqlite.org/capi3ref.html#sqlite3_step
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*/
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int ustep () {
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int ret = ::sqlite3_step (statement);
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if (ret == SQLITE_DONE) {
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mChanges = ::sqlite3_changes (*session);
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return mChanges;
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}
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if (ret == SQLITE_ROW) return 0;
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throw SqliteEx (std::string(::sqlite3_errmsg(*session)));
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}
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/**
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* The number of rows changed by the query.
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* Providing the query was a DML (Data Modification Language),
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* returns the number of rows updated.\n
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* If the query wasn't a DML, returned value is undefined.\n
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* -1 is returned if the query wasn't executed, or after #reset.\n
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* Example: \code
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* SqliteQuery query (&ses, S("update test set count = count + ? where id = ?"));
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* query.bind (1, 1);
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* query.bind (2, 9);
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* query.step ();
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* int affected = query.changes ();
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* \endcode
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* @see #ustep
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*/
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int changes () {return mChanges;}
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/**
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* The integer value of the given column.
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* @param column 1-based.
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* @see http://sqlite.org/capi3ref.html#sqlite3_column_text
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*/
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int intAt (int column) {
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return ::sqlite3_column_int (statement, --column);
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}
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/**
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* The integer value of the given column.
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* @param column 1-based.
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* @see http://sqlite.org/capi3ref.html#sqlite3_column_text
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*/
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sqlite3_int64 int64at (int column) {
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return ::sqlite3_column_int64 (statement, --column);
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}
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/**
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* The floating point number from the given column.
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* @param column 1-based.
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* @see http://sqlite.org/capi3ref.html#sqlite3_column_text
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*/
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double doubleAt (int column) {
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return ::sqlite3_column_double (statement, --column);
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}
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/**
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* Return the column as UTF-8 characters, which can be used until the next #step.
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* @param column 1-based.
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* @see http://sqlite.org/capi3ref.html#sqlite3_column_text
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*/
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std::pair<char const*, int> charsAt (int column) {
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return std::pair<char const*, int> ((char const*) ::sqlite3_column_text (statement, column-1),
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::sqlite3_column_bytes (statement, column-1));
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}
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/**
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* Return the column as C++ string (UTF-8).
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* @param column 1-based.
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*/
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std::string stringAt (int column) {
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return std::string ((char const*) ::sqlite3_column_text (statement, column-1),
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::sqlite3_column_bytes (statement, column-1));
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}
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/**
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* The type of the column.
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* SQLITE_INTEGER, SQLITE_FLOAT, SQLITE_TEXT, SQLITE_BLOB or SQLITE_NULL.
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* @param column 1-based.
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* @see http://sqlite.org/capi3ref.html#sqlite3_column_text
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*/
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int typeAt (int column) {
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return ::sqlite3_column_type (statement, --column);
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}
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/**
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* Binds a value using one of the bind methods.
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*/
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template<typename T>
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SqliteQuery& operator << (T value) {
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return bind (++bindCounter, value);
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}
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/**
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* Binds a value using the named parameter and one of the bind methods.
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* @throws SqliteEx if the name could not be found.
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* @see http://sqlite.org/capi3ref.html#sqlite3_bind_parameter_index
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*/
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template<typename T>
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SqliteQuery& bind (char const* name, T value) {
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int index = ::sqlite3_bind_parameter_index (statement, name);
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if (index == 0)
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throw SqliteEx (std::string ("No such parameter in the query: ") + name);
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return bind (index, value);
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}
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/**
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* Bind a string to the query.
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* @param transient must be true, if lifetime of the string might be shorter than that of the query.
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*/
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SqliteQuery& bind (int index, const char* text, int length, bool transient = false) {
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if (::sqlite3_bind_text (statement, index, text, length,
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transient ? SQLITE_TRANSIENT : SQLITE_STATIC) != SQLITE_OK)
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throw SqliteEx (std::string (::sqlite3_errmsg (*session)));
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return *this;
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}
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/**
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* Bind a string to the query.
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* @param transient must be true, if lifetime of the string might be shorter than that of the query.
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*/
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SqliteQuery& bind (int index, std::pair<const char*, int> text, bool transient = false) {
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if (::sqlite3_bind_text (statement, index, text.first, text.second,
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transient ? SQLITE_TRANSIENT : SQLITE_STATIC) != SQLITE_OK)
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throw SqliteEx (std::string (::sqlite3_errmsg (*session)));
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return *this;
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}
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/**
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* Bind a string to the query.
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* @param transient must be true, if lifetime of the string might be shorter than that of the query.
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*/
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SqliteQuery& bind (int index, const std::string& text, bool transient = true) {
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if (::sqlite3_bind_text (statement, index, text.data(), text.length(),
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transient ? SQLITE_TRANSIENT : SQLITE_STATIC) != SQLITE_OK)
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throw SqliteEx (std::string (::sqlite3_errmsg (*session)));
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return *this;
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}
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/**
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* Bind an integer to the query.
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*/
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SqliteQuery& bind (int index, int value) {
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if (::sqlite3_bind_int (statement, index, value) != SQLITE_OK)
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throw SqliteEx (std::string (::sqlite3_errmsg (*session)));
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return *this;
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}
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/**
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* Bind an 64-bit integer to the query.
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*/
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SqliteQuery& bind (int index, sqlite3_int64 value) {
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if (::sqlite3_bind_int64 (statement, index, value) != SQLITE_OK)
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throw SqliteEx (std::string (::sqlite3_errmsg (*session)));
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return *this;
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}
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};
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/**
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* Version of SqliteQuery suitable for using SQLite in parallel with other processes.
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* Will automatically handle the SQLITE_SCHEMA error
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* and will automatically repeat attempts after SQLITE_BUSY,
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* but it requires that the query string supplied
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* is constant and available during the SqliteParQuery lifetime.
|
|
* Error messages, contained in exceptions, may differ from SqliteQuery by containing the query
|
|
* (for example, the #step method will throw "$query: $errmsg" instead of just "$errmsg").
|
|
*/
|
|
class SqliteParQuery: public SqliteQuery {
|
|
protected:
|
|
char const* query;
|
|
int queryLength;
|
|
int repeat;
|
|
int wait;
|
|
public:
|
|
/**
|
|
* Prepares the query.
|
|
* @param repeat the number of times we try to repeat the query when SQLITE_BUSY is returned.
|
|
* @param wait how long, in milliseconds (1/1000 of a second) we are to wait before repeating.
|
|
* @throws SqliteEx if sqlite3_prepare fails; format of the error message is "$query: $errmsg".
|
|
*/
|
|
SqliteParQuery (SqliteSession* session, char const* query, int queryLength, int repeat = 90, int wait = 20)
|
|
: SqliteQuery (session, query, queryLength) {
|
|
this->query = query;
|
|
this->queryLength = queryLength;
|
|
this->repeat = repeat;
|
|
this->wait = wait;
|
|
}
|
|
/**
|
|
* Prepares the query.
|
|
* @param query the SQL query together with its length.
|
|
* @param repeat the number of times we try to repeat the query when SQLITE_BUSY is returned.
|
|
* @param wait how long, in milliseconds (1/1000 of a second) we are to wait before repeating.
|
|
* @throws SqliteEx if sqlite3_prepare fails; format of the error message is "$query: $errmsg".
|
|
*/
|
|
SqliteParQuery (SqliteSession* session, std::pair<char const*, int> query, int repeat = 90, int wait = 20)
|
|
: SqliteQuery (session, query) {
|
|
this->query = query.first;
|
|
this->queryLength = query.second;
|
|
this->repeat = repeat;
|
|
this->wait = wait;
|
|
}
|
|
|
|
bool next () {return step();}
|
|
bool step () {
|
|
if (mChanges >= 0) {mChanges = 0; return false;}
|
|
repeat:
|
|
int ret = ::sqlite3_step (statement);
|
|
if (ret == SQLITE_ROW) return true;
|
|
if (ret == SQLITE_DONE) {
|
|
mChanges = ::sqlite3_changes (*session);
|
|
return false;
|
|
}
|
|
if (ret == SQLITE_SCHEMA) {
|
|
::sqlite3_stmt* old = statement;
|
|
prepare (session, query, queryLength);
|
|
::sqlite3_transfer_bindings(old, statement);
|
|
::sqlite3_finalize (old);
|
|
goto repeat;
|
|
}
|
|
if (ret == SQLITE_BUSY) for (int repeat = this->repeat; ret == SQLITE_BUSY && repeat >= 0; --repeat) {
|
|
//struct timespec ts; ts.tv_sec = 0; ts.tv_nsec = wait * 1000000; // nan is 10^-9 of sec.
|
|
//while (::nanosleep (&ts, &ts) == EINTR);
|
|
::sqlite3_sleep (wait);
|
|
ret = ::sqlite3_step (statement);
|
|
}
|
|
throw SqliteEx (std::string(query, queryLength) + ::sqlite3_errmsg(*session));
|
|
}
|
|
};
|
|
|
|
template <typename T>
|
|
SqliteQuery SqliteSession::query (T t) {
|
|
return SqliteQuery (this, t);
|
|
}
|
|
|
|
}; // namespace glim
|
|
|
|
#endif // GLIM_SQLITE_HPP_
|