The Database class encapsulates a single connection to a SQLite3 database. Its usage is very straightforward:

  require 'sqlite3'

  db = SQLite3::Database.new( "data.db" )

  db.execute( "select * from table" ) do |row|
    p row
  end

  db.close

It wraps the lower-level methods provides by the selected driver, and includes the Pragmas module for access to various pragma convenience methods.

The Database class provides type translation services as well, by which the SQLite3 data types (which are all represented as strings) may be converted into their corresponding types (as defined in the schemas for their tables). This translation only occurs when querying data from the database—insertions and updates are all still typeless.

Furthermore, the Database class has been designed to work well with the ArrayFields module from Ara Howard. If you require the ArrayFields module before performing a query, and if you have not enabled results as hashes, then the results will all be indexible by field name.

Methods
Included Modules
Attributes
[R] driver A reference to the underlying SQLite3 driver used by this database.
[R] handle The low-level opaque database handle that this object wraps.
[RW] results_as_hash A boolean that indicates whether rows in result sets should be returned as hashes or not. By default, rows are returned as arrays.
[RW] type_translation A boolean indicating whether or not type translation is enabled for this database.
Classes and Modules
Class SQLite3::Database::FunctionProxy
Public Class methods
new( file_name, options={} )

Create a new Database object that opens the given file. If utf16 is true, the filename is interpreted as a UTF-16 encoded string.

By default, the new database will return result rows as arrays (results_as_hash) and has type translation disabled (type_translation=).

     # File lib/sqlite3/database.rb, line 105
105:     def initialize( file_name, options={} )
106:       utf16 = options.fetch(:utf16, false)
107:       load_driver( options[:driver] )
108: 
109:       @statement_factory = options[:statement_factory] || Statement
110: 
111:       result, @handle = @driver.open( file_name, utf16 )
112:       Error.check( result, nil, "could not open database" )
113: 
114:       @closed = false
115:       @results_as_hash = options.fetch(:results_as_hash,false)
116:       @type_translation = options.fetch(:type_translation,false)
117:       @translator = nil
118:     end
quote( string )

Quotes the given string, making it safe to use in an SQL statement. It replaces all instances of the single-quote character with two single-quote characters. The modified string is returned.

    # File lib/sqlite3/database.rb, line 80
80:       def quote( string )
81:         string.gsub( /'/, "''" )
82:       end
Public Instance methods
authorizer( data=nil, &block )

Installs (or removes) a block that will be invoked for every access to the database. If the block returns 0 (or nil), the statement is allowed to proceed. Returning 1 causes an authorization error to occur, and returning 2 causes the access to be silently denied.

     # File lib/sqlite3/database.rb, line 175
175:     def authorizer( data=nil, &block )
176:       result = @driver.set_authorizer( @handle, data, &block )
177:       Error.check( result, self )
178:     end
busy_handler( data=nil ) {|data, retries| ...}

Register a busy handler with this database instance. When a requested resource is busy, this handler will be invoked. If the handler returns false, the operation will be aborted; otherwise, the resource will be requested again.

The handler will be invoked with the name of the resource that was busy, and the number of times it has been retried.

See also busy_timeout.

     # File lib/sqlite3/database.rb, line 338
338:     def busy_handler( data=nil, &block ) # :yields: data, retries
339:       result = @driver.busy_handler( @handle, data, &block )
340:       Error.check( result, self )
341:     end
busy_timeout( ms )

Indicates that if a request for a resource terminates because that resource is busy, SQLite should wait for the indicated number of milliseconds before trying again. By default, SQLite does not retry busy resources. To restore the default behavior, send 0 as the ms parameter.

See also busy_handler.

     # File lib/sqlite3/database.rb, line 350
350:     def busy_timeout( ms )
351:       result = @driver.busy_timeout( @handle, ms )
352:       Error.check( result, self )
353:     end
changes()

Returns the number of changes made to this database instance by the last operation performed. Note that a "delete from table" without a where clause will not affect this value.

     # File lib/sqlite3/database.rb, line 314
314:     def changes
315:       @driver.changes( @handle )
316:     end
close()

Closes this database.

     # File lib/sqlite3/database.rb, line 150
150:     def close
151:       unless @closed
152:         result = @driver.close( @handle )
153:         Error.check( result, self )
154:       end
155:       @closed = true
156:     end
closed?()

Returns true if this database instance has been closed (see close).

     # File lib/sqlite3/database.rb, line 159
159:     def closed?
160:       @closed
161:     end
commit()

Commits the current transaction. If there is no current transaction, this will cause an error to be raised. This returns true, in order to allow it to be used in idioms like abort? and rollback or commit.

     # File lib/sqlite3/database.rb, line 609
609:     def commit
610:       execute "commit transaction"
611:       @transaction_active = false
612:       true
613:     end
complete?( string, utf16=false )

Return true if the string is a valid (ie, parsable) SQL statement, and false otherwise. If +utf16+ is true, then the string is a UTF-16 character string.

     # File lib/sqlite3/database.rb, line 123
123:     def complete?( string, utf16=false )
124:       @driver.complete?( string, utf16 )
125:     end
create_aggregate( name, arity, step=nil, finalize=nil, text_rep=Constants::TextRep::ANY, &block )

Creates a new aggregate function for use in SQL statements. Aggregate functions are functions that apply over every row in the result set, instead of over just a single row. (A very common aggregate function is the "count" function, for determining the number of rows that match a query.)

The new function will be added as name, with the given arity. (For variable arity functions, use -1 for the arity.)

The step parameter must be a proc object that accepts as its first parameter a FunctionProxy instance (representing the function invocation), with any subsequent parameters (up to the function’s arity). The step callback will be invoked once for each row of the result set.

The finalize parameter must be a proc object that accepts only a single parameter, the FunctionProxy instance representing the current function invocation. It should invoke FunctionProxy#set_result to store the result of the function.

Example:

  db.create_aggregate( "lengths", 1 ) do
    step do |func, value|
      func[ :total ] ||= 0
      func[ :total ] += ( value ? value.length : 0 )
    end

    finalize do |func|
      func.set_result( func[ :total ] || 0 )
    end
  end

  puts db.get_first_value( "select lengths(name) from table" )

See also create_aggregate_handler for a more object-oriented approach to aggregate functions.

     # File lib/sqlite3/database.rb, line 434
434:     def create_aggregate( name, arity, step=nil, finalize=nil,
435:       text_rep=Constants::TextRep::ANY, &block )
436:     # begin
437:       if block
438:         proxy = AggregateDefinitionProxy.new
439:         proxy.instance_eval &block
440:         step ||= proxy.step_callback
441:         finalize ||= proxy.finalize_callback
442:       end
443: 
444:       step_callback = proc do |func,*args|
445:         ctx = @driver.aggregate_context( func )
446:         unless ctx[:__error]
447:           begin
448:             step.call( FunctionProxy.new( @driver, func, ctx ),
449:               *args.map{|v| Value.new(self,v)} )
450:           rescue Exception => e
451:             ctx[:__error] = e
452:           end
453:         end
454:       end
455: 
456:       finalize_callback = proc do |func|
457:         ctx = @driver.aggregate_context( func )
458:         unless ctx[:__error]
459:           begin
460:             finalize.call( FunctionProxy.new( @driver, func, ctx ) )
461:           rescue Exception => e
462:             @driver.result_error( func,
463:               "#{e.message} (#{e.class})", -1 )
464:           end
465:         else
466:           e = ctx[:__error]
467:           @driver.result_error( func,
468:             "#{e.message} (#{e.class})", -1 )
469:         end
470:       end
471: 
472:       result = @driver.create_function( @handle, name, arity, text_rep, nil,
473:         nil, step_callback, finalize_callback )
474:       Error.check( result, self )
475: 
476:       self
477:     end
create_aggregate_handler( handler )

This is another approach to creating an aggregate function (see create_aggregate). Instead of explicitly specifying the name, callbacks, arity, and type, you specify a factory object (the "handler") that knows how to obtain all of that information. The handler should respond to the following messages:

arity:corresponds to the arity parameter of create_aggregate. This message is optional, and if the handler does not respond to it, the function will have an arity of -1.
name:this is the name of the function. The handler must implement this message.
new:this must be implemented by the handler. It should return a new instance of the object that will handle a specific invocation of the function.

The handler instance (the object returned by the new message, described above), must respond to the following messages:

step:this is the method that will be called for each step of the aggregate function’s evaluation. It should implement the same signature as the step callback for create_aggregate.
finalize:this is the method that will be called to finalize the aggregate function’s evaluation. It should implement the same signature as the finalize callback for create_aggregate.

Example:

  class LengthsAggregateHandler
    def self.arity; 1; end

    def initialize
      @total = 0
    end

    def step( ctx, name )
      @total += ( name ? name.length : 0 )
    end

    def finalize( ctx )
      ctx.set_result( @total )
    end
  end

  db.create_aggregate_handler( LengthsAggregateHandler )
  puts db.get_first_value( "select lengths(name) from A" )
     # File lib/sqlite3/database.rb, line 525
525:     def create_aggregate_handler( handler )
526:       arity = -1
527:       text_rep = Constants::TextRep::ANY
528: 
529:       arity = handler.arity if handler.respond_to?(:arity)
530:       text_rep = handler.text_rep if handler.respond_to?(:text_rep)
531:       name = handler.name
532: 
533:       step = proc do |func,*args|
534:         ctx = @driver.aggregate_context( func )
535:         unless ctx[ :__error ]
536:           ctx[ :handler ] ||= handler.new
537:           begin
538:             ctx[ :handler ].step( FunctionProxy.new( @driver, func, ctx ),
539:               *args.map{|v| Value.new(self,v)} )
540:           rescue Exception, StandardError => e
541:             ctx[ :__error ] = e
542:           end
543:         end
544:       end
545: 
546:       finalize = proc do |func|
547:         ctx = @driver.aggregate_context( func )
548:         unless ctx[ :__error ]
549:           ctx[ :handler ] ||= handler.new
550:           begin
551:             ctx[ :handler ].finalize( FunctionProxy.new( @driver, func, ctx ) )
552:           rescue Exception => e
553:             ctx[ :__error ] = e
554:           end
555:         end
556: 
557:         if ctx[ :__error ]
558:           e = ctx[ :__error ]
559:           @driver.sqlite3_result_error( func, "#{e.message} (#{e.class})", -1 )
560:         end
561:       end
562: 
563:       result = @driver.create_function( @handle, name, arity, text_rep, nil,
564:         nil, step, finalize )
565:       Error.check( result, self )
566: 
567:       self
568:     end
create_function( name, arity, text_rep=Constants::TextRep::ANY ) {|func, *args| ...}

Creates a new function for use in SQL statements. It will be added as name, with the given arity. (For variable arity functions, use -1 for the arity.)

The block should accept at least one parameter—the FunctionProxy instance that wraps this function invocation—and any other arguments it needs (up to its arity).

The block does not return a value directly. Instead, it will invoke the FunctionProxy#set_result method on the func parameter and indicate the return value that way.

Example:

  db.create_function( "maim", 1 ) do |func, value|
    if value.nil?
      func.result = nil
    else
      func.result = value.split(//).sort.join
    end
  end

  puts db.get_first_value( "select maim(name) from table" )
     # File lib/sqlite3/database.rb, line 378
378:     def create_function( name, arity, text_rep=Constants::TextRep::ANY,
379:       &block ) # :yields: func, *args
380:     # begin
381:       callback = proc do |func,*args|
382:         begin
383:           block.call( FunctionProxy.new( @driver, func ),
384:             *args.map{|v| Value.new(self,v)} )
385:         rescue StandardError, Exception => e
386:           @driver.result_error( func,
387:             "#{e.message} (#{e.class})", -1 )
388:         end
389:       end
390: 
391:       result = @driver.create_function( @handle, name, arity, text_rep, nil,
392:         callback, nil, nil )
393:       Error.check( result, self )
394: 
395:       self
396:     end
errcode()

Return an integer representing the last error to have occurred with this database.

     # File lib/sqlite3/database.rb, line 135
135:     def errcode
136:       @driver.errcode( @handle )
137:     end
errmsg( utf16=false )

Return a string describing the last error to have occurred with this database.

     # File lib/sqlite3/database.rb, line 129
129:     def errmsg( utf16=false )
130:       @driver.errmsg( @handle, utf16 )
131:     end
execute( sql, *bind_vars ) {|row| ...}

Executes the given SQL statement. If additional parameters are given, they are treated as bind variables, and are bound to the placeholders in the query.

Note that if any of the values passed to this are hashes, then the key/value pairs are each bound separately, with the key being used as the name of the placeholder to bind the value to.

The block is optional. If given, it will be invoked for each row returned by the query. Otherwise, any results are accumulated into an array and returned wholesale.

See also execute2, query, and execute_batch for additional ways of executing statements.

     # File lib/sqlite3/database.rb, line 209
209:     def execute( sql, *bind_vars )
210:       prepare( sql ) do |stmt|
211:         result = stmt.execute( *bind_vars )
212:         if block_given?
213:           result.each { |row| yield row }
214:         else
215:           return result.inject( [] ) { |arr,row| arr << row; arr }
216:         end
217:       end
218:     end
execute2( sql, *bind_vars ) {|result.columns| ...}

Executes the given SQL statement, exactly as with execute. However, the first row returned (either via the block, or in the returned array) is always the names of the columns. Subsequent rows correspond to the data from the result set.

Thus, even if the query itself returns no rows, this method will always return at least one row—the names of the columns.

See also execute, query, and execute_batch for additional ways of executing statements.

     # File lib/sqlite3/database.rb, line 230
230:     def execute2( sql, *bind_vars )
231:       prepare( sql ) do |stmt|
232:         result = stmt.execute( *bind_vars )
233:         if block_given?
234:           yield result.columns
235:           result.each { |row| yield row }
236:         else
237:           return result.inject( [ result.columns ] ) { |arr,row|
238:             arr << row; arr }
239:         end
240:       end
241:     end
execute_batch( sql, *bind_vars )

Executes all SQL statements in the given string. By contrast, the other means of executing queries will only execute the first statement in the string, ignoring all subsequent statements. This will execute each one in turn. The same bind parameters, if given, will be applied to each statement.

This always returns nil, making it unsuitable for queries that return rows.

     # File lib/sqlite3/database.rb, line 251
251:     def execute_batch( sql, *bind_vars )
252:       sql = sql.strip
253:       until sql.empty? do
254:         prepare( sql ) do |stmt|
255:           stmt.execute( *bind_vars )
256:           sql = stmt.remainder.strip
257:         end
258:       end
259:       nil
260:     end
get_first_row( sql, *bind_vars )

A convenience method for obtaining the first row of a result set, and discarding all others. It is otherwise identical to execute.

See also get_first_value.

     # File lib/sqlite3/database.rb, line 290
290:     def get_first_row( sql, *bind_vars )
291:       execute( sql, *bind_vars ) { |row| return row }
292:       nil
293:     end
get_first_value( sql, *bind_vars )

A convenience method for obtaining the first value of the first row of a result set, and discarding all other values and rows. It is otherwise identical to execute.

See also get_first_row.

     # File lib/sqlite3/database.rb, line 300
300:     def get_first_value( sql, *bind_vars )
301:       execute( sql, *bind_vars ) { |row| return row[0] }
302:       nil
303:     end
interrupt()

Interrupts the currently executing operation, causing it to abort.

     # File lib/sqlite3/database.rb, line 325
325:     def interrupt
326:       @driver.interrupt( @handle )
327:     end
last_insert_row_id()

Obtains the unique row ID of the last row to be inserted by this Database instance.

     # File lib/sqlite3/database.rb, line 307
307:     def last_insert_row_id
308:       @driver.last_insert_rowid( @handle )
309:     end
prepare( sql ) {|stmt| ...}

Returns a Statement object representing the given SQL. This does not execute the statement; it merely prepares the statement for execution.

     # File lib/sqlite3/database.rb, line 182
182:     def prepare( sql )
183:       stmt = @statement_factory.new( self, sql )
184:       if block_given?
185:         begin
186:           yield stmt
187:         ensure
188:           stmt.close
189:         end
190:       else
191:         return stmt
192:       end
193:     end
query( sql, *bind_vars ) {|result| ...}

This is a convenience method for creating a statement, binding paramters to it, and calling execute:

  result = db.query( "select * from foo where a=?", 5 )
  # is the same as
  result = db.prepare( "select * from foo where a=?" ).execute( 5 )

You must be sure to call close on the ResultSet instance that is returned, or you could have problems with locks on the table. If called with a block, close will be invoked implicitly when the block terminates.

     # File lib/sqlite3/database.rb, line 273
273:     def query( sql, *bind_vars )
274:       result = prepare( sql ).execute( *bind_vars )
275:       if block_given?
276:         begin
277:           yield result
278:         ensure
279:           result.close
280:         end
281:       else
282:         return result
283:       end
284:     end
rollback()

Rolls the current transaction back. If there is no current transaction, this will cause an error to be raised. This returns true, in order to allow it to be used in idioms like abort? and rollback or commit.

     # File lib/sqlite3/database.rb, line 619
619:     def rollback
620:       execute "rollback transaction"
621:       @transaction_active = false
622:       true
623:     end
total_changes()

Returns the total number of changes made to this database instance since it was opened.

     # File lib/sqlite3/database.rb, line 320
320:     def total_changes
321:       @driver.total_changes( @handle )
322:     end
trace( data=nil, &block )

Installs (or removes) a block that will be invoked for every SQL statement executed. The block receives a two parameters: the data argument, and the SQL statement executed. If the block is nil, any existing tracer will be uninstalled.

     # File lib/sqlite3/database.rb, line 167
167:     def trace( data=nil, &block )
168:       @driver.trace( @handle, data, &block )
169:     end
transaction( mode = :deferred ) {|self| ...}

Begins a new transaction. Note that nested transactions are not allowed by SQLite, so attempting to nest a transaction will result in a runtime exception.

The mode parameter may be either :deferred (the default), :immediate, or :exclusive.

If a block is given, the database instance is yielded to it, and the transaction is committed when the block terminates. If the block raises an exception, a rollback will be performed instead. Note that if a block is given, commit and rollback should never be called explicitly or you’ll get an error when the block terminates.

If a block is not given, it is the caller’s responsibility to end the transaction explicitly, either by calling commit, or by calling rollback.

     # File lib/sqlite3/database.rb, line 586
586:     def transaction( mode = :deferred )
587:       execute "begin #{mode.to_s} transaction"
588:       @transaction_active = true
589: 
590:       if block_given?
591:         abort = false
592:         begin
593:           yield self
594:         rescue Exception
595:           abort = true
596:           raise
597:         ensure
598:           abort and rollback or commit
599:         end
600:       end
601: 
602:       true
603:     end
transaction_active?()

Returns true if there is a transaction active, and false otherwise.

     # File lib/sqlite3/database.rb, line 626
626:     def transaction_active?
627:       @transaction_active
628:     end
translator()

Return the type translator employed by this database instance. Each database instance has its own type translator; this allows for different type handlers to be installed in each instance without affecting other instances. Furthermore, the translators are instantiated lazily, so that if a database does not use type translation, it will not be burdened by the overhead of a useless type translator. (See the Translator class.)

     # File lib/sqlite3/database.rb, line 145
145:     def translator
146:       @translator ||= Translator.new
147:     end

[Validate]