716 lines
24 KiB
Ruby
716 lines
24 KiB
Ruby
require 'sqlite3/constants'
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require 'sqlite3/errors'
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require 'sqlite3/pragmas'
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require 'sqlite3/statement'
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require 'sqlite3/translator'
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require 'sqlite3/value'
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module SQLite3
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# The Database class encapsulates a single connection to a SQLite3 database.
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# Its usage is very straightforward:
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#
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# require 'sqlite3'
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#
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# db = SQLite3::Database.new( "data.db" )
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#
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# db.execute( "select * from table" ) do |row|
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# p row
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# end
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#
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# db.close
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#
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# It wraps the lower-level methods provides by the selected driver, and
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# includes the Pragmas module for access to various pragma convenience
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# methods.
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#
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# The Database class provides type translation services as well, by which
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# the SQLite3 data types (which are all represented as strings) may be
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# converted into their corresponding types (as defined in the schemas
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# for their tables). This translation only occurs when querying data from
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# the database--insertions and updates are all still typeless.
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#
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# Furthermore, the Database class has been designed to work well with the
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# ArrayFields module from Ara Howard. If you require the ArrayFields
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# module before performing a query, and if you have not enabled results as
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# hashes, then the results will all be indexible by field name.
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class Database
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include Pragmas
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class <<self
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alias :open :new
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# Quotes the given string, making it safe to use in an SQL statement.
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# It replaces all instances of the single-quote character with two
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# single-quote characters. The modified string is returned.
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def quote( string )
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string.gsub( /'/, "''" )
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end
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end
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# The low-level opaque database handle that this object wraps.
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attr_reader :handle
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# A reference to the underlying SQLite3 driver used by this database.
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attr_reader :driver
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# A boolean that indicates whether rows in result sets should be returned
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# as hashes or not. By default, rows are returned as arrays.
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attr_accessor :results_as_hash
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# A boolean indicating whether or not type translation is enabled for this
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# database.
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attr_accessor :type_translation
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# Create a new Database object that opens the given file. If utf16
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# is +true+, the filename is interpreted as a UTF-16 encoded string.
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#
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# By default, the new database will return result rows as arrays
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# (#results_as_hash) and has type translation disabled (#type_translation=).
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def initialize( file_name, options={} )
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utf16 = options.fetch(:utf16, false)
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load_driver( options[:driver] )
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@statement_factory = options[:statement_factory] || Statement
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result, @handle = @driver.open( file_name, utf16 )
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Error.check( result, self, "could not open database" )
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@closed = false
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@results_as_hash = options.fetch(:results_as_hash,false)
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@type_translation = options.fetch(:type_translation,false)
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@translator = nil
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@transaction_active = false
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end
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# Return +true+ if the string is a valid (ie, parsable) SQL statement, and
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# +false+ otherwise. If +utf16+ is +true+, then the string is a UTF-16
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# character string.
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def complete?( string, utf16=false )
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@driver.complete?( string, utf16 )
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end
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# Return a string describing the last error to have occurred with this
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# database.
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def errmsg( utf16=false )
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@driver.errmsg( @handle, utf16 )
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end
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# Return an integer representing the last error to have occurred with this
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# database.
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def errcode
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@driver.errcode( @handle )
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end
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# Return the type translator employed by this database instance. Each
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# database instance has its own type translator; this allows for different
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# type handlers to be installed in each instance without affecting other
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# instances. Furthermore, the translators are instantiated lazily, so that
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# if a database does not use type translation, it will not be burdened by
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# the overhead of a useless type translator. (See the Translator class.)
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def translator
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@translator ||= Translator.new
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end
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# Closes this database.
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def close
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unless @closed
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result = @driver.close( @handle )
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Error.check( result, self )
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end
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@closed = true
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end
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# Returns +true+ if this database instance has been closed (see #close).
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def closed?
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@closed
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end
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# Installs (or removes) a block that will be invoked for every SQL
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# statement executed. The block receives a two parameters: the +data+
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# argument, and the SQL statement executed. If the block is +nil+,
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# any existing tracer will be uninstalled.
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def trace( data=nil, &block )
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@driver.trace( @handle, data, &block )
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end
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# Installs (or removes) a block that will be invoked for every access
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# to the database. If the block returns 0 (or +nil+), the statement
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# is allowed to proceed. Returning 1 causes an authorization error to
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# occur, and returning 2 causes the access to be silently denied.
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def authorizer( data=nil, &block )
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result = @driver.set_authorizer( @handle, data, &block )
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Error.check( result, self )
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end
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# Returns a Statement object representing the given SQL. This does not
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# execute the statement; it merely prepares the statement for execution.
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#
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# The Statement can then be executed using Statement#execute.
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#
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def prepare( sql )
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stmt = @statement_factory.new( self, sql )
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if block_given?
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begin
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yield stmt
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ensure
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stmt.close
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end
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else
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return stmt
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end
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end
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# Executes the given SQL statement. If additional parameters are given,
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# they are treated as bind variables, and are bound to the placeholders in
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# the query.
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#
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# Note that if any of the values passed to this are hashes, then the
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# key/value pairs are each bound separately, with the key being used as
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# the name of the placeholder to bind the value to.
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#
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# The block is optional. If given, it will be invoked for each row returned
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# by the query. Otherwise, any results are accumulated into an array and
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# returned wholesale.
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#
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# See also #execute2, #query, and #execute_batch for additional ways of
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# executing statements.
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def execute( sql, *bind_vars )
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prepare( sql ) do |stmt|
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result = stmt.execute( *bind_vars )
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if block_given?
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result.each { |row| yield row }
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else
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return result.inject( [] ) { |arr,row| arr << row; arr }
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end
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end
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end
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# Executes the given SQL statement, exactly as with #execute. However, the
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# first row returned (either via the block, or in the returned array) is
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# always the names of the columns. Subsequent rows correspond to the data
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# from the result set.
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#
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# Thus, even if the query itself returns no rows, this method will always
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# return at least one row--the names of the columns.
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#
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# See also #execute, #query, and #execute_batch for additional ways of
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# executing statements.
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def execute2( sql, *bind_vars )
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prepare( sql ) do |stmt|
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result = stmt.execute( *bind_vars )
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if block_given?
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yield result.columns
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result.each { |row| yield row }
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else
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return result.inject( [ result.columns ] ) { |arr,row|
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arr << row; arr }
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end
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end
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end
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# Executes all SQL statements in the given string. By contrast, the other
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# means of executing queries will only execute the first statement in the
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# string, ignoring all subsequent statements. This will execute each one
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# in turn. The same bind parameters, if given, will be applied to each
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# statement.
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#
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# This always returns +nil+, making it unsuitable for queries that return
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# rows.
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def execute_batch( sql, *bind_vars )
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sql = sql.strip
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until sql.empty? do
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prepare( sql ) do |stmt|
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stmt.execute( *bind_vars )
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sql = stmt.remainder.strip
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end
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end
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nil
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end
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# This is a convenience method for creating a statement, binding
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# paramters to it, and calling execute:
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#
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# result = db.query( "select * from foo where a=?", 5 )
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# # is the same as
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# result = db.prepare( "select * from foo where a=?" ).execute( 5 )
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#
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# You must be sure to call +close+ on the ResultSet instance that is
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# returned, or you could have problems with locks on the table. If called
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# with a block, +close+ will be invoked implicitly when the block
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# terminates.
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def query( sql, *bind_vars )
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result = prepare( sql ).execute( *bind_vars )
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if block_given?
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begin
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yield result
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ensure
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result.close
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end
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else
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return result
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end
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end
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# A convenience method for obtaining the first row of a result set, and
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# discarding all others. It is otherwise identical to #execute.
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#
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# See also #get_first_value.
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def get_first_row( sql, *bind_vars )
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execute( sql, *bind_vars ) { |row| return row }
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nil
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end
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# A convenience method for obtaining the first value of the first row of a
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# result set, and discarding all other values and rows. It is otherwise
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# identical to #execute.
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#
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# See also #get_first_row.
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def get_first_value( sql, *bind_vars )
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execute( sql, *bind_vars ) { |row| return row[0] }
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nil
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end
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# Obtains the unique row ID of the last row to be inserted by this Database
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# instance.
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def last_insert_row_id
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@driver.last_insert_rowid( @handle )
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end
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# Returns the number of changes made to this database instance by the last
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# operation performed. Note that a "delete from table" without a where
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# clause will not affect this value.
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def changes
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@driver.changes( @handle )
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end
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# Returns the total number of changes made to this database instance
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# since it was opened.
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def total_changes
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@driver.total_changes( @handle )
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end
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# Interrupts the currently executing operation, causing it to abort.
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def interrupt
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@driver.interrupt( @handle )
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end
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# Register a busy handler with this database instance. When a requested
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# resource is busy, this handler will be invoked. If the handler returns
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# +false+, the operation will be aborted; otherwise, the resource will
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# be requested again.
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#
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# The handler will be invoked with the name of the resource that was
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# busy, and the number of times it has been retried.
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#
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# See also the mutually exclusive #busy_timeout.
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def busy_handler( data=nil, &block ) # :yields: data, retries
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result = @driver.busy_handler( @handle, data, &block )
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Error.check( result, self )
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end
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# Indicates that if a request for a resource terminates because that
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# resource is busy, SQLite should sleep and retry for up to the indicated
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# number of milliseconds. By default, SQLite does not retry
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# busy resources. To restore the default behavior, send 0 as the
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# +ms+ parameter.
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#
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# See also the mutually exclusive #busy_handler.
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def busy_timeout( ms )
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result = @driver.busy_timeout( @handle, ms )
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Error.check( result, self )
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end
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# Creates a new function for use in SQL statements. It will be added as
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# +name+, with the given +arity+. (For variable arity functions, use
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# -1 for the arity.)
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#
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# The block should accept at least one parameter--the FunctionProxy
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# instance that wraps this function invocation--and any other
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# arguments it needs (up to its arity).
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#
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# The block does not return a value directly. Instead, it will invoke
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# the FunctionProxy#set_result method on the +func+ parameter and
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# indicate the return value that way.
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#
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# Example:
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#
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# db.create_function( "maim", 1 ) do |func, value|
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# if value.nil?
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# func.result = nil
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# else
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# func.result = value.split(//).sort.join
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# end
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# end
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#
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# puts db.get_first_value( "select maim(name) from table" )
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def create_function( name, arity, text_rep=Constants::TextRep::ANY,
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&block ) # :yields: func, *args
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# begin
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callback = proc do |func,*args|
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begin
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block.call( FunctionProxy.new( @driver, func ),
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*args.map{|v| Value.new(self,v)} )
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rescue StandardError, Exception => e
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@driver.result_error( func,
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"#{e.message} (#{e.class})", -1 )
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end
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end
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result = @driver.create_function( @handle, name, arity, text_rep, nil,
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callback, nil, nil )
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Error.check( result, self )
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self
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end
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# Creates a new aggregate function for use in SQL statements. Aggregate
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# functions are functions that apply over every row in the result set,
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# instead of over just a single row. (A very common aggregate function
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# is the "count" function, for determining the number of rows that match
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# a query.)
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#
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# The new function will be added as +name+, with the given +arity+. (For
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# variable arity functions, use -1 for the arity.)
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#
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# The +step+ parameter must be a proc object that accepts as its first
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# parameter a FunctionProxy instance (representing the function
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# invocation), with any subsequent parameters (up to the function's arity).
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# The +step+ callback will be invoked once for each row of the result set.
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#
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# The +finalize+ parameter must be a +proc+ object that accepts only a
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# single parameter, the FunctionProxy instance representing the current
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# function invocation. It should invoke FunctionProxy#set_result to
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# store the result of the function.
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#
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# Example:
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#
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# db.create_aggregate( "lengths", 1 ) do
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# step do |func, value|
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# func[ :total ] ||= 0
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# func[ :total ] += ( value ? value.length : 0 )
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# end
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#
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# finalize do |func|
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# func.set_result( func[ :total ] || 0 )
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# end
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# end
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#
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# puts db.get_first_value( "select lengths(name) from table" )
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#
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# See also #create_aggregate_handler for a more object-oriented approach to
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# aggregate functions.
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def create_aggregate( name, arity, step=nil, finalize=nil,
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text_rep=Constants::TextRep::ANY, &block )
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# begin
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if block
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proxy = AggregateDefinitionProxy.new
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proxy.instance_eval(&block)
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step ||= proxy.step_callback
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finalize ||= proxy.finalize_callback
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end
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step_callback = proc do |func,*args|
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ctx = @driver.aggregate_context( func )
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unless ctx[:__error]
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begin
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step.call( FunctionProxy.new( @driver, func, ctx ),
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*args.map{|v| Value.new(self,v)} )
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rescue Exception => e
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ctx[:__error] = e
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end
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end
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end
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finalize_callback = proc do |func|
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ctx = @driver.aggregate_context( func )
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unless ctx[:__error]
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begin
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finalize.call( FunctionProxy.new( @driver, func, ctx ) )
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rescue Exception => e
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@driver.result_error( func,
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"#{e.message} (#{e.class})", -1 )
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end
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else
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e = ctx[:__error]
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@driver.result_error( func,
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"#{e.message} (#{e.class})", -1 )
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end
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end
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result = @driver.create_function( @handle, name, arity, text_rep, nil,
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nil, step_callback, finalize_callback )
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Error.check( result, self )
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self
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end
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# This is another approach to creating an aggregate function (see
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# #create_aggregate). Instead of explicitly specifying the name,
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# callbacks, arity, and type, you specify a factory object
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# (the "handler") that knows how to obtain all of that information. The
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# handler should respond to the following messages:
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#
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# +arity+:: corresponds to the +arity+ parameter of #create_aggregate. This
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# message is optional, and if the handler does not respond to it,
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# the function will have an arity of -1.
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# +name+:: this is the name of the function. The handler _must_ implement
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# this message.
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# +new+:: this must be implemented by the handler. It should return a new
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# instance of the object that will handle a specific invocation of
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# the function.
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#
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# The handler instance (the object returned by the +new+ message, described
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# above), must respond to the following messages:
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#
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# +step+:: this is the method that will be called for each step of the
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# aggregate function's evaluation. It should implement the same
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# signature as the +step+ callback for #create_aggregate.
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# +finalize+:: this is the method that will be called to finalize the
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# aggregate function's evaluation. It should implement the
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# same signature as the +finalize+ callback for
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# #create_aggregate.
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#
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# Example:
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#
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# class LengthsAggregateHandler
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# def self.arity; 1; end
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#
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# def initialize
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# @total = 0
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# end
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#
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# def step( ctx, name )
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# @total += ( name ? name.length : 0 )
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# end
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#
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# def finalize( ctx )
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# ctx.set_result( @total )
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# end
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# end
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#
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# db.create_aggregate_handler( LengthsAggregateHandler )
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# puts db.get_first_value( "select lengths(name) from A" )
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def create_aggregate_handler( handler )
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arity = -1
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text_rep = Constants::TextRep::ANY
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arity = handler.arity if handler.respond_to?(:arity)
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text_rep = handler.text_rep if handler.respond_to?(:text_rep)
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name = handler.name
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step = proc do |func,*args|
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ctx = @driver.aggregate_context( func )
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unless ctx[ :__error ]
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ctx[ :handler ] ||= handler.new
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begin
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ctx[ :handler ].step( FunctionProxy.new( @driver, func, ctx ),
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*args.map{|v| Value.new(self,v)} )
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rescue Exception, StandardError => e
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ctx[ :__error ] = e
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end
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end
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end
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finalize = proc do |func|
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ctx = @driver.aggregate_context( func )
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unless ctx[ :__error ]
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ctx[ :handler ] ||= handler.new
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begin
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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
|
|
|