class SQLite3::Database
hashes, then the results will all be indexible by field name.
module before performing a query, and if you have not enabled results as
ArrayFields module from Ara Howard. If you require the ArrayFields
Furthermore, the Database class has been designed to work well with the
the database–insertions and updates are all still typeless.
for their tables). This translation only occurs when querying data from
converted into their corresponding types (as defined in the schemas
the SQLite3 data types (which are all represented as strings) may be
The Database class provides type translation services as well, by which
methods.
includes the Pragmas module for access to various pragma convenience
It wraps the lower-level methods provides by the selected driver, and
end
end
p row
db.execute( “select * from table” ) do |row|
SQLite3::Database.new( “data.db” ) do |db|
require ‘sqlite3’
Its usage is very straightforward:
The Database class encapsulates a single connection to a SQLite3 database.
def self.arity
def self.arity @arity end
def self.arity
def self.arity # this is what sqlite3_obj_method_arity did before @template.method(:step).arity end
def self.finalize( &block )
def self.finalize( &block ) define_method(:finalize_with_ctx, &block) end
def self.name
def self.name @name end
def self.name
def self.name @name end
def self.step( &block )
def self.step( &block ) define_method(:step_with_ctx, &block) end
def self.template
def self.template @template end
def authorizer( &block )
is allowed to proceed. Returning 1 causes an authorization error to
to the database. If the block returns 0 (or +nil+), the statement
Installs (or removes) a block that will be invoked for every access
def authorizer( &block ) self.authorizer = block end
def commit
to allow it to be used in idioms like
this will cause an error to be raised. This returns +true+, in order
Commits the current transaction. If there is no current transaction,
def commit execute "commit transaction" true end
def create_aggregate( name, arity, step=nil, finalize=nil,
See also #create_aggregate_handler for a more object-oriented approach to
puts db.get_first_value( "select lengths(name) from table" )
end
end
func.result = func[ :total ] || 0
finalize do |func|
end
func[ :total ] += ( value ? value.length : 0 )
func[ :total ] ||= 0
step do |func, value|
db.create_aggregate( "lengths", 1 ) do
Example:
store the result of the function.
function invocation. It should invoke FunctionProxy#result= to
single parameter, the FunctionProxy instance representing the current
The +finalize+ parameter must be a +proc+ object that accepts only a
The +step+ callback will be invoked once for each row of the result set.
invocation), with any subsequent parameters (up to the function's arity).
parameter a FunctionProxy instance (representing the function
The +step+ parameter must be a proc object that accepts as its first
variable arity functions, use -1 for the arity.)
The new function will be added as +name+, with the given +arity+. (For
a query.)
is the "count" function, for determining the number of rows that match
instead of over just a single row. (A very common aggregate function
functions are functions that apply over every row in the result set,
Creates a new aggregate function for use in SQL statements. Aggregate
def create_aggregate( name, arity, step=nil, finalize=nil, text_rep=Constants::TextRep::ANY, &block ) proxy = Class.new do def self.step( &block ) define_method(:step_with_ctx, &block) end def self.finalize( &block ) define_method(:finalize_with_ctx, &block) end end if block_given? proxy.instance_eval(&block) else proxy.class_eval do define_method(:step_with_ctx, step) define_method(:finalize_with_ctx, finalize) end end proxy.class_eval do # class instance variables @name = name @arity = arity def self.name @name end def self.arity @arity end def initialize @ctx = FunctionProxy.new end def step( *args ) step_with_ctx(@ctx, *args) end def finalize finalize_with_ctx(@ctx) @ctx.result end end define_aggregator2(proxy, name) end
def create_aggregate_handler( handler )
db.create_aggregate_handler( LengthsAggregateHandler )
end
end
ctx.result = @total
def finalize( ctx )
end
@total += ( name ? name.length : 0 )
def step( ctx, name )
end
@total = 0
def initialize
def self.name; 'lengths'; end
def self.arity; 1; end
class LengthsAggregateHandler
Example:
#create_aggregate.
same signature as the +finalize+ callback for
aggregate function's evaluation. It should implement the
+finalize+:: this is the method that will be called to finalize the
signature as the +step+ callback for #create_aggregate.
aggregate function's evaluation. It should implement the same
+step+:: this is the method that will be called for each step of the
above), must respond to the following messages:
The handler instance (the object returned by the +new+ message, described
the function.
instance of the object that will handle a specific invocation of
+new+:: this must be implemented by the handler. It should return a new
this message.
+name+:: this is the name of the function. The handler _must_ implement
the function will have an arity of -1.
message is optional, and if the handler does not respond to it,
+arity+:: corresponds to the +arity+ parameter of #create_aggregate. This
handler should respond to the following messages:
(the "handler") that knows how to obtain all of that information. The
callbacks, arity, and type, you specify a factory object
#create_aggregate). Instead of explicitly specifying the name,
This is another approach to creating an aggregate function (see
def create_aggregate_handler( handler ) # This is a compatiblity shim so the (basically pointless) FunctionProxy # "ctx" object is passed as first argument to both step() and finalize(). # Now its up to the library user whether he prefers to store his # temporaries as instance varibales or fields in the FunctionProxy. # The library user still must set the result value with # FunctionProxy.result= as there is no backwards compatible way to # change this. proxy = Class.new(handler) do def initialize super @fp = FunctionProxy.new end def step( *args ) super(@fp, *args) end def finalize super(@fp) @fp.result end end define_aggregator2(proxy, proxy.name) self end
def create_function name, arity, text_rep=Constants::TextRep::UTF8, &block
end
end
func.result = value.split(//).sort.join
else
func.result = nil
if value.nil?
db.create_function( "maim", 1 ) do |func, value|
Example:
indicate the return value that way.
the FunctionProxy#result= method on the +func+ parameter and
The block does not return a value directly. Instead, it will invoke
arguments it needs (up to its arity).
instance that wraps this function invocation--and any other
The block should accept at least one parameter--the FunctionProxy
-1 for the arity.)
+name+, with the given +arity+. (For variable arity functions, use
Creates a new function for use in SQL statements. It will be added as
def create_function name, arity, text_rep=Constants::TextRep::UTF8, &block define_function_with_flags(name, text_rep) do |*args| fp = FunctionProxy.new block.call(fp, *args) fp.result end self end
def define_aggregator( name, aggregator )
already provide a suitable +clone+.
individual instances of the aggregate function. Regular ruby objects
+aggregator+ object will serve as template that is cloned to provide the
_API Change:_ +aggregator+ must also implement +clone+. The provided
return value for the aggregator function.
+step+ will be called with row information and +finalize+ must return the
object +aggregator+. +aggregator+ must respond to +step+ and +finalize+.
Define an aggregate function named +name+ using a object template
def define_aggregator( name, aggregator ) # Previously, this has been implemented in C. Now this is just yet # another compatiblity shim proxy = Class.new do @template = aggregator @name = name def self.template @template end def self.name @name end def self.arity # this is what sqlite3_obj_method_arity did before @template.method(:step).arity end def initialize @klass = self.class.template.clone end def step(*args) @klass.step(*args) end def finalize @klass.finalize end end define_aggregator2(proxy, name) self end
def execute sql, bind_vars = [], *args, &block
See also #execute2, #query, and #execute_batch for additional ways of
returned wholesale.
by the query. Otherwise, any results are accumulated into an array and
The block is optional. If given, it will be invoked for each row returned
the name of the placeholder to bind the value to.
key/value pairs are each bound separately, with the key being used as
Note that if any of the values passed to this are hashes, then the
the query.
they are treated as bind variables, and are bound to the placeholders in
Executes the given SQL statement. If additional parameters are given,
def execute sql, bind_vars = [], *args, &block if bind_vars.nil? || !args.empty? if args.empty? bind_vars = [] else bind_vars = [bind_vars] + args end warn(<<-eowarn) if $VERBOSE ller[0]} is calling SQLite3::Database#execute with nil or multiple bind params out using an array. Please switch to passing bind parameters as an array. ort for bind parameters as *args will be removed in 2.0.0. eowarn end prepare( sql ) do |stmt| stmt.bind_params(bind_vars) stmt = ResultSet.new self, stmt if block_given? stmt.each do |row| yield row end else stmt.to_a end end end
def execute2( sql, *bind_vars )
See also #execute, #query, and #execute_batch for additional ways of
return at least one row--the names of the columns.
Thus, even if the query itself returns no rows, this method will always
from the result set.
always the names of the columns. Subsequent rows correspond to the data
first row returned (either via the block, or in the returned array) is
Executes the given SQL statement, exactly as with #execute. However, the
def execute2( sql, *bind_vars ) prepare( sql ) do |stmt| result = stmt.execute( *bind_vars ) if block_given? yield stmt.columns result.each { |row| yield row } else return result.inject( [ stmt.columns ] ) { |arr,row| arr << row; arr } end end end
def execute_batch( sql, bind_vars = [], *args )
See also #execute_batch2 for additional ways of
rows.
This always returns +nil+, making it unsuitable for queries that return
statement.
in turn. The same bind parameters, if given, will be applied to each
string, ignoring all subsequent statements. This will execute each one
means of executing queries will only execute the first statement in the
Executes all SQL statements in the given string. By contrast, the other
def execute_batch( sql, bind_vars = [], *args ) # FIXME: remove this stuff later unless [Array, Hash].include?(bind_vars.class) bind_vars = [bind_vars] warn(<<-eowarn) if $VERBOSE ller[0]} is calling SQLite3::Database#execute_batch with bind parameters are not a list of a hash. Please switch to passing bind parameters as an y or hash. Support for this behavior will be removed in version 2.0.0. eowarn end # FIXME: remove this stuff later if bind_vars.nil? || !args.empty? if args.empty? bind_vars = [] else bind_vars = [nil] + args end warn(<<-eowarn) if $VERBOSE ller[0]} is calling SQLite3::Database#execute_batch with nil or multiple bind params out using an array. Please switch to passing bind parameters as an array. ort for this behavior will be removed in version 2.0.0. eowarn end sql = sql.strip until sql.empty? do prepare( sql ) do |stmt| unless stmt.closed? # FIXME: this should probably use sqlite3's api for batch execution # This implementation requires stepping over the results. if bind_vars.length == stmt.bind_parameter_count stmt.bind_params(bind_vars) end stmt.step end sql = stmt.remainder.strip end end # FIXME: we should not return `nil` as a success return value nil end
def execute_batch2(sql, &block)
See also #execute_batch for additional ways of
a block can be passed to parse the values accordingly.
Because all values except for 'NULL' are returned as strings,
If no query is made, an empty array will be returned.
If a query is made, all values will be returned as strings.
in turn. Bind parameters cannot be passed to #execute_batch2.
string, ignoring all subsequent statements. This will execute each one
means of executing queries will only execute the first statement in the
Executes all SQL statements in the given string. By contrast, the other
def execute_batch2(sql, &block) if block_given? result = exec_batch(sql, @results_as_hash) result.map do |val| yield val end else exec_batch(sql, @results_as_hash) end end
def filename db_name = 'main'
to "main". Main return `nil` or an empty string if the database is
Returns the filename for the database named +db_name+. +db_name+ defaults
def filename db_name = 'main' db_filename db_name end
def finalize
def finalize finalize_with_ctx(@ctx) @ctx.result end
def finalize
def finalize super(@fp) @fp.result end
def finalize
def finalize @klass.finalize end
def get_first_row( sql, *bind_vars )
discarding all others. It is otherwise identical to #execute.
A convenience method for obtaining the first row of a result set, and
def get_first_row( sql, *bind_vars ) execute( sql, *bind_vars ).first end
def get_first_value( sql, *bind_vars )
identical to #execute.
result set, and discarding all other values and rows. It is otherwise
A convenience method for obtaining the first value of the first row of a
def get_first_value( sql, *bind_vars ) query( sql, bind_vars ) do |rs| if (row = rs.next) return @results_as_hash ? row[rs.columns[0]] : row[0] end end nil end
def initialize file, options = {}, zvfs = nil
def initialize file, options = {}, zvfs = nil mode = Constants::Open::READWRITE | Constants::Open::CREATE if file.encoding == ::Encoding::UTF_16LE || file.encoding == ::Encoding::UTF_16BE || options[:utf16] open16 file else # The three primary flag values for sqlite3_open_v2 are: # SQLITE_OPEN_READONLY # SQLITE_OPEN_READWRITE # SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE -- always used for sqlite3_open and sqlite3_open16 mode = Constants::Open::READONLY if options[:readonly] if options[:readwrite] raise "conflicting options: readonly and readwrite" if options[:readonly] mode = Constants::Open::READWRITE end if options[:flags] if options[:readonly] || options[:readwrite] raise "conflicting options: flags with readonly and/or readwrite" end mode = options[:flags] end open_v2 file.encode("utf-8"), mode, zvfs end @tracefunc = nil @authorizer = nil @encoding = nil @busy_handler = nil @collations = {} @functions = {} @results_as_hash = options[:results_as_hash] @type_translation = options[:type_translation] @type_translator = make_type_translator @type_translation @readonly = mode & Constants::Open::READONLY != 0 if block_given? begin yield self ensure close end end end
def initialize
def initialize @ctx = FunctionProxy.new end
def initialize
def initialize super @fp = FunctionProxy.new end
def initialize
def initialize @klass = self.class.template.clone end
def make_type_translator should_translate
def make_type_translator should_translate if should_translate lambda { |types, row| types.zip(row).map do |type, value| translator.translate( type, value ) end } else NULL_TRANSLATOR end end
def prepare sql
The Statement can then be executed using Statement#execute.
execute the statement; it merely prepares the statement for execution.
Returns a Statement object representing the given SQL. This does not
def prepare sql stmt = SQLite3::Statement.new( self, sql ) return stmt unless block_given? begin yield stmt ensure stmt.close unless stmt.closed? end end
def query( sql, bind_vars = [], *args )
with a block, +close+ will be invoked implicitly when the block
returned, or you could have problems with locks on the table. If called
You must be sure to call +close+ on the ResultSet instance that is
result = db.prepare( "select * from foo where a=?" ).execute( 5 )
# is the same as
result = db.query( "select * from foo where a=?", [5])
paramters to it, and calling execute:
This is a convenience method for creating a statement, binding
def query( sql, bind_vars = [], *args ) if bind_vars.nil? || !args.empty? if args.empty? bind_vars = [] else bind_vars = [bind_vars] + args end warn(<<-eowarn) if $VERBOSE ller[0]} is calling SQLite3::Database#query with nil or multiple bind params out using an array. Please switch to passing bind parameters as an array. ort for this will be removed in version 2.0.0. eowarn end result = prepare( sql ).execute( bind_vars ) if block_given? begin yield result ensure result.close end else return result end end
def quote( string )
It replaces all instances of the single-quote character with two
Quotes the given string, making it safe to use in an SQL statement.
def quote( string ) string.gsub( /'/, "''" ) end
def readonly?
Returns +true+ if the database has been open in readonly mode
def readonly? @readonly end
def rollback
to allow it to be used in idioms like
this will cause an error to be raised. This returns +true+, in order
Rolls the current transaction back. If there is no current transaction,
def rollback execute "rollback transaction" true end
def step( *args )
def step( *args ) step_with_ctx(@ctx, *args) end
def step( *args )
def step( *args ) super(@fp, *args) end
def step(*args)
def step(*args) @klass.step(*args) end
def transaction( mode = :deferred )
transaction explicitly, either by calling #commit, or by calling
If a block is not given, it is the caller's responsibility to end the
explicitly or you'll get an error when the block terminates.
a block is given, #commit and #rollback should never be called
raises an exception, a rollback will be performed instead. Note that if
transaction is committed when the block terminates. If the block
If a block is given, the database instance is yielded to it, and the
:immediate, or :exclusive.
The +mode+ parameter may be either :deferred (the default),
exception.
by SQLite, so attempting to nest a transaction will result in a runtime
Begins a new transaction. Note that nested transactions are not allowed
def transaction( mode = :deferred ) execute "begin #{mode.to_s} transaction" if block_given? abort = false begin yield self rescue abort = true raise ensure abort and rollback or commit end end true end
def translate_from_db types, row
def translate_from_db types, row @type_translator.call types, row end
def translator
if a database does not use type translation, it will not be burdened by
instances. Furthermore, the translators are instantiated lazily, so that
type handlers to be installed in each instance without affecting other
database instance has its own type translator; this allows for different
Return the type translator employed by this database instance. Each
def translator @translator ||= Translator.new end
def type_translation= value # :nodoc:
def type_translation= value # :nodoc: warn(<<-eowarn) if $VERBOSE ller[0]} is calling SQLite3::Database#type_translation= te3::Database#type_translation= is deprecated and will be removed ersion 2.0.0. eowarn @type_translator = make_type_translator value @type_translation = value end