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https://github.com/sparklemotion/sqlite3-ruby

Ruby bindings for the SQLite3 embedded database
https://github.com/sparklemotion/sqlite3-ruby

ruby sqlite

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Ruby bindings for the SQLite3 embedded database

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README 

        
# Ruby Interface for SQLite3



## Overview



This library allows Ruby programs to use the SQLite3 database engine (http://www.sqlite.org).



Note that this module is only compatible with SQLite 3.6.16 or newer.



* Source code: https://github.com/sparklemotion/sqlite3-ruby

* Mailing list: http://groups.google.com/group/sqlite3-ruby

* Download: http://rubygems.org/gems/sqlite3

* Documentation: https://sparklemotion.github.io/sqlite3-ruby/



[![Test suite](https://github.com/sparklemotion/sqlite3-ruby/actions/workflows/ci.yml/badge.svg)](https://github.com/sparklemotion/sqlite3-ruby/actions/workflows/ci.yml)



## Quick start



For help understanding the SQLite3 Ruby API, please read the [FAQ](./FAQ.md) and the [full API documentation](https://sparklemotion.github.io/sqlite3-ruby/).



A few key classes whose APIs are often-used are:



- SQLite3::Database ([rdoc](https://sparklemotion.github.io/sqlite3-ruby/SQLite3/Database.html))

- SQLite3::Statement ([rdoc](https://sparklemotion.github.io/sqlite3-ruby/SQLite3/Statement.html))

- SQLite3::ResultSet ([rdoc](https://sparklemotion.github.io/sqlite3-ruby/SQLite3/ResultSet.html))



If you have any questions that you feel should be addressed in the FAQ, please send them to [the mailing list](http://groups.google.com/group/sqlite3-ruby) or open a [discussion thread](https://github.com/sparklemotion/sqlite3-ruby/discussions/categories/q-a).



``` ruby

require "sqlite3"



# Open a database

db = SQLite3::Database.new "test.db"



# Create a table

rows = db.execute <<-SQL

  create table numbers (

    name varchar(30),

    val int

  );

SQL



# Execute a few inserts

{

  "one" => 1,

  "two" => 2,

}.each do |pair|

  db.execute "insert into numbers values ( ?, ? )", pair

end



# Find a few rows

db.execute( "select * from numbers" ) do |row|

  p row

end

# => ["one", 1]

#    ["two", 2]



# Create another table with multiple columns

db.execute <<-SQL

  create table students (

    name varchar(50),

    email varchar(50),

    grade varchar(5),

    blog varchar(50)

  );

SQL



# Execute inserts with parameter markers

db.execute("INSERT INTO students (name, email, grade, blog)

            VALUES (?, ?, ?, ?)", ["Jane", "[email protected]", "A", "http://blog.janedoe.com"])



db.execute( "select * from students" ) do |row|

  p row

end

# => ["Jane", "[email protected]", "A", "http://blog.janedoe.com"]

```



## Thread Safety



When `SQLite3.threadsafe?` returns `true`, then SQLite3 has been compiled to

support running in a multithreaded environment.  However, this doesn't mean

that all classes in the SQLite3 gem can be considered "thread safe".



When `SQLite3.threadsafe?` returns `true`, it is safe to share only

`SQLite3::Database` instances among threads without providing your own locking

mechanism.  For example, the following code is fine because only the database

instance is shared among threads:



```ruby

require 'sqlite3'



db = SQLite3::Database.new ":memory:"



latch = Queue.new



ts = 10.times.map {

  Thread.new {

    latch.pop

    db.execute "SELECT '#{Thread.current.inspect}'"

  }

}

10.times { latch << nil }



p ts.map(&:value)

```



Other instances can be shared among threads, but they require that you provide

your own locking for thread safety.  For example, `SQLite3::Statement` objects

(prepared statements) are mutable, so applications must take care to add

appropriate locks to avoid data race conditions when sharing these objects

among threads.



Lets rewrite the above example but use a prepared statement and safely share

the prepared statement among threads:



```ruby

db = SQLite3::Database.new ":memory:"



# Prepare a statement

stmt = db.prepare "SELECT :inspect"

stmt_lock = Mutex.new



latch = Queue.new



ts = 10.times.map {

  Thread.new {

    latch.pop



    # Add a lock when using the prepared statement.

    # Binding values, and walking over results will mutate the statement, so

    # in order to prevent other threads from "seeing" this thread's data, we

    # must lock when using the statement object

    stmt_lock.synchronize do

      stmt.execute(Thread.current.inspect).to_a

    end

  }

}



10.times { latch << nil }



p ts.map(&:value)



stmt.close

```



It is generally recommended that if applications want to share a database among

threads, they _only_ share the database instance object.  Other objects are

fine to share, but may require manual locking for thread safety.



## Fork Safety



[Sqlite is not fork

safe](https://www.sqlite.org/howtocorrupt.html#_carrying_an_open_database_connection_across_a_fork_)

and instructs users to not carry an open writable database connection across a `fork()`. Using an inherited

connection in the child may corrupt your database, leak memory, or cause other undefined behavior.



To help protect users of this gem from accidental corruption due to this lack of fork safety, the gem will immediately close any open writable databases in the child after a fork. Discarding writable

connections in the child will incur a small one-time memory leak per connection, but that's

preferable to potentially corrupting your database.



Whenever possible, close writable connections in the parent before forking. If absolutely necessary (and you know what you're doing), you may suppress the fork safety warnings by calling `SQLite3::ForkSafety.suppress_warnings!`.



See [./adr/2024-09-fork-safety.md](./adr/2024-09-fork-safety.md) for more information and context.



## Support



### Installation or database extensions



If you're having trouble with installation, please first read [`INSTALLATION.md`](./INSTALLATION.md).



### General help requests



You can ask for help or support:



* by emailing the [sqlite3-ruby mailing list](http://groups.google.com/group/sqlite3-ruby)

* by opening a [discussion thread](https://github.com/sparklemotion/sqlite3-ruby/discussions/categories/q-a) on Github



### Bug reports



You can file the bug at the [github issues page](https://github.com/sparklemotion/sqlite3-ruby/issues).



## Contributing



See [`CONTRIBUTING.md`](./CONTRIBUTING.md).



## License



This library is licensed under `BSD-3-Clause`, see [`LICENSE`](./LICENSE).



### Dependencies



The source code of `sqlite` is distributed in the "ruby platform" gem. This code is public domain,

see https://www.sqlite.org/copyright.html for details.