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Jacques Distler 2007-01-22 07:43:50 -06:00
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#--
# =============================================================================
# Copyright (c) 2004, Jamis Buck (jgb3@email.byu.edu)
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
#
# * Redistributions of source code must retain the above copyright notice,
# this list of conditions and the following disclaimer.
#
# * Redistributions in binary form must reproduce the above copyright
# notice, this list of conditions and the following disclaimer in the
# documentation and/or other materials provided with the distribution.
#
# * The names of its contributors may not be used to endorse or promote
# products derived from this software without specific prior written
# permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
# DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
# SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
# =============================================================================
#++
require 'base64'
require 'sqlite3/constants'
require 'sqlite3/errors'
require 'sqlite3/pragmas'
require 'sqlite3/statement'
require 'sqlite3/translator'
require 'sqlite3/value'
module SQLite3
# 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.
class Database
include Pragmas
class <<self
alias :open :new
# 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.
def quote( string )
string.gsub( /'/, "''" )
end
end
# The low-level opaque database handle that this object wraps.
attr_reader :handle
# A reference to the underlying SQLite3 driver used by this database.
attr_reader :driver
# A boolean that indicates whether rows in result sets should be returned
# as hashes or not. By default, rows are returned as arrays.
attr_accessor :results_as_hash
# A boolean indicating whether or not type translation is enabled for this
# database.
attr_accessor :type_translation
# 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=).
def initialize( file_name, options={} )
utf16 = options.fetch(:utf16, false)
load_driver( options[:driver] )
@statement_factory = options[:statement_factory] || Statement
result, @handle = @driver.open( file_name, utf16 )
Error.check( result, self, "could not open database" )
@closed = false
@results_as_hash = options.fetch(:results_as_hash,false)
@type_translation = options.fetch(:type_translation,false)
@translator = nil
@transaction_active = false
end
# 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.
def complete?( string, utf16=false )
@driver.complete?( string, utf16 )
end
# Return a string describing the last error to have occurred with this
# database.
def errmsg( utf16=false )
@driver.errmsg( @handle, utf16 )
end
# Return an integer representing the last error to have occurred with this
# database.
def errcode
@driver.errcode( @handle )
end
# 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.)
def translator
@translator ||= Translator.new
end
# Closes this database.
def close
unless @closed
result = @driver.close( @handle )
Error.check( result, self )
end
@closed = true
end
# Returns +true+ if this database instance has been closed (see #close).
def closed?
@closed
end
# 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.
def trace( data=nil, &block )
@driver.trace( @handle, data, &block )
end
# 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.
def authorizer( data=nil, &block )
result = @driver.set_authorizer( @handle, data, &block )
Error.check( result, self )
end
# Returns a Statement object representing the given SQL. This does not
# execute the statement; it merely prepares the statement for execution.
def prepare( sql )
stmt = @statement_factory.new( self, sql )
if block_given?
begin
yield stmt
ensure
stmt.close
end
else
return stmt
end
end
# 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.
def execute( sql, *bind_vars )
prepare( sql ) do |stmt|
result = stmt.execute( *bind_vars )
if block_given?
result.each { |row| yield row }
else
return result.inject( [] ) { |arr,row| arr << row; arr }
end
end
end
# 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.
def execute2( sql, *bind_vars )
prepare( sql ) do |stmt|
result = stmt.execute( *bind_vars )
if block_given?
yield result.columns
result.each { |row| yield row }
else
return result.inject( [ result.columns ] ) { |arr,row|
arr << row; arr }
end
end
end
# 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.
def execute_batch( sql, *bind_vars )
sql = sql.strip
until sql.empty? do
prepare( sql ) do |stmt|
stmt.execute( *bind_vars )
sql = stmt.remainder.strip
end
end
nil
end
# 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.
def query( sql, *bind_vars )
result = prepare( sql ).execute( *bind_vars )
if block_given?
begin
yield result
ensure
result.close
end
else
return result
end
end
# 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.
def get_first_row( sql, *bind_vars )
execute( sql, *bind_vars ) { |row| return row }
nil
end
# 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.
def get_first_value( sql, *bind_vars )
execute( sql, *bind_vars ) { |row| return row[0] }
nil
end
# Obtains the unique row ID of the last row to be inserted by this Database
# instance.
def last_insert_row_id
@driver.last_insert_rowid( @handle )
end
# 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.
def changes
@driver.changes( @handle )
end
# Returns the total number of changes made to this database instance
# since it was opened.
def total_changes
@driver.total_changes( @handle )
end
# Interrupts the currently executing operation, causing it to abort.
def interrupt
@driver.interrupt( @handle )
end
# 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.
def busy_handler( data=nil, &block ) # :yields: data, retries
result = @driver.busy_handler( @handle, data, &block )
Error.check( result, self )
end
# 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.
def busy_timeout( ms )
result = @driver.busy_timeout( @handle, ms )
Error.check( result, self )
end
# 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" )
def create_function( name, arity, text_rep=Constants::TextRep::ANY,
&block ) # :yields: func, *args
# begin
callback = proc do |func,*args|
begin
block.call( FunctionProxy.new( @driver, func ),
*args.map{|v| Value.new(self,v)} )
rescue StandardError, Exception => e
@driver.result_error( func,
"#{e.message} (#{e.class})", -1 )
end
end
result = @driver.create_function( @handle, name, arity, text_rep, nil,
callback, nil, nil )
Error.check( result, self )
self
end
# 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.
def create_aggregate( name, arity, step=nil, finalize=nil,
text_rep=Constants::TextRep::ANY, &block )
# begin
if block
proxy = AggregateDefinitionProxy.new
proxy.instance_eval(&block)
step ||= proxy.step_callback
finalize ||= proxy.finalize_callback
end
step_callback = proc do |func,*args|
ctx = @driver.aggregate_context( func )
unless ctx[:__error]
begin
step.call( FunctionProxy.new( @driver, func, ctx ),
*args.map{|v| Value.new(self,v)} )
rescue Exception => e
ctx[:__error] = e
end
end
end
finalize_callback = proc do |func|
ctx = @driver.aggregate_context( func )
unless ctx[:__error]
begin
finalize.call( FunctionProxy.new( @driver, func, ctx ) )
rescue Exception => e
@driver.result_error( func,
"#{e.message} (#{e.class})", -1 )
end
else
e = ctx[:__error]
@driver.result_error( func,
"#{e.message} (#{e.class})", -1 )
end
end
result = @driver.create_function( @handle, name, arity, text_rep, nil,
nil, step_callback, finalize_callback )
Error.check( result, self )
self
end
# 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" )
def create_aggregate_handler( handler )
arity = -1
text_rep = Constants::TextRep::ANY
arity = handler.arity if handler.respond_to?(:arity)
text_rep = handler.text_rep if handler.respond_to?(:text_rep)
name = handler.name
step = proc do |func,*args|
ctx = @driver.aggregate_context( func )
unless ctx[ :__error ]
ctx[ :handler ] ||= handler.new
begin
ctx[ :handler ].step( FunctionProxy.new( @driver, func, ctx ),
*args.map{|v| Value.new(self,v)} )
rescue Exception, StandardError => e
ctx[ :__error ] = e
end
end
end
finalize = proc do |func|
ctx = @driver.aggregate_context( func )
unless ctx[ :__error ]
ctx[ :handler ] ||= handler.new
begin
ctx[ :handler ].finalize( FunctionProxy.new( @driver, func, ctx ) )
rescue Exception => e
ctx[ :__error ] = e
end
end
if ctx[ :__error ]
e = ctx[ :__error ]
@driver.sqlite3_result_error( func, "#{e.message} (#{e.class})", -1 )
end
end
result = @driver.create_function( @handle, name, arity, text_rep, nil,
nil, step, finalize )
Error.check( result, self )
self
end
# 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 <tt>:deferred</tt> (the default),
# <tt>:immediate</tt>, or <tt>:exclusive</tt>.
#
# 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.
def transaction( mode = :deferred )
execute "begin #{mode.to_s} transaction"
@transaction_active = true
if block_given?
abort = false
begin
yield self
rescue ::Object
abort = true
raise
ensure
abort and rollback or commit
end
end
true
end
# 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
# <tt>abort? and rollback or commit</tt>.
def commit
execute "commit transaction"
@transaction_active = false
true
end
# 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
# <tt>abort? and rollback or commit</tt>.
def rollback
execute "rollback transaction"
@transaction_active = false
true
end
# Returns +true+ if there is a transaction active, and +false+ otherwise.
def transaction_active?
@transaction_active
end
# Loads the corresponding driver, or if it is nil, attempts to locate a
# suitable driver.
def load_driver( driver )
case driver
when Class
# do nothing--use what was given
when Symbol, String
require "sqlite3/driver/#{driver.to_s.downcase}/driver"
driver = SQLite3::Driver.const_get( driver )::Driver
else
[ "Native", "DL" ].each do |d|
begin
require "sqlite3/driver/#{d.downcase}/driver"
driver = SQLite3::Driver.const_get( d )::Driver
break
rescue SyntaxError
raise
rescue ScriptError, Exception, NameError
end
end
raise "no driver for sqlite3 found" unless driver
end
@driver = driver.new
end
private :load_driver
# A helper class for dealing with custom functions (see #create_function,
# #create_aggregate, and #create_aggregate_handler). It encapsulates the
# opaque function object that represents the current invocation. It also
# provides more convenient access to the API functions that operate on
# the function object.
#
# This class will almost _always_ be instantiated indirectly, by working
# with the create methods mentioned above.
class FunctionProxy
# Create a new FunctionProxy that encapsulates the given +func+ object.
# If context is non-nil, the functions context will be set to that. If
# it is non-nil, it must quack like a Hash. If it is nil, then none of
# the context functions will be available.
def initialize( driver, func, context=nil )
@driver = driver
@func = func
@context = context
end
# Calls #set_result to set the result of this function.
def result=( result )
set_result( result )
end
# Set the result of the function to the given value. The function will
# then return this value.
def set_result( result, utf16=false )
@driver.result_text( @func, result, utf16 )
end
# Set the result of the function to the given error message.
# The function will then return that error.
def set_error( error )
@driver.result_error( @func, error.to_s, -1 )
end
# (Only available to aggregate functions.) Returns the number of rows
# that the aggregate has processed so far. This will include the current
# row, and so will always return at least 1.
def count
ensure_aggregate!
@driver.aggregate_count( @func )
end
# Returns the value with the given key from the context. This is only
# available to aggregate functions.
def []( key )
ensure_aggregate!
@context[ key ]
end
# Sets the value with the given key in the context. This is only
# available to aggregate functions.
def []=( key, value )
ensure_aggregate!
@context[ key ] = value
end
# A function for performing a sanity check, to ensure that the function
# being invoked is an aggregate function. This is implied by the
# existence of the context variable.
def ensure_aggregate!
unless @context
raise MisuseException, "function is not an aggregate"
end
end
private :ensure_aggregate!
end
# A proxy used for defining the callbacks to an aggregate function.
class AggregateDefinitionProxy # :nodoc:
attr_reader :step_callback, :finalize_callback
def step( &block )
@step_callback = block
end
def finalize( &block )
@finalize_callback = block
end
end
end
end