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Checkout of Instiki Trunk 1/21/2007.

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Jacques Distler 2007-01-22 07:43:50 -06:00
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vendor/plugins/sqlite3-ruby/sqlite3/statement.rb vendored Normal file
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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 'sqlite3/errors'
require 'sqlite3/resultset'
class String
def to_blob
SQLite3::Blob.new( self )
end
end
module SQLite3
# A class for differentiating between strings and blobs, when binding them
# into statements.
class Blob < String; end
# A statement represents a prepared-but-unexecuted SQL query. It will rarely
# (if ever) be instantiated directly by a client, and is most often obtained
# via the Database#prepare method.
class Statement
# This is any text that followed the first valid SQL statement in the text
# with which the statement was initialized. If there was no trailing text,
# this will be the empty string.
attr_reader :remainder
# The underlying opaque handle used to access the SQLite @driver.
attr_reader :handle
# Create a new statement attached to the given Database instance, and which
# encapsulates the given SQL text. If the text contains more than one
# statement (i.e., separated by semicolons), then the #remainder property
# will be set to the trailing text.
def initialize( db, sql, utf16=false )
@db = db
@driver = @db.driver
@closed = false
@results = @columns = nil
result, @handle, @remainder = @driver.prepare( @db.handle, sql )
Error.check( result, @db )
end
# Closes the statement by finalizing the underlying statement
# handle. The statement must not be used after being closed.
def close
must_be_open!
@closed = true
@driver.finalize( @handle )
end
# Returns true if the underlying statement has been closed.
def closed?
@closed
end
# Binds the given variables to the corresponding placeholders in the SQL
# text.
#
# See Database#execute for a description of the valid placeholder
# syntaxes.
#
# Example:
#
# stmt = db.prepare( "select * from table where a=? and b=?" )
# stmt.bind_params( 15, "hello" )
#
# See also #execute, #bind_param, Statement#bind_param, and
# Statement#bind_params.
def bind_params( *bind_vars )
index = 1
bind_vars.flatten.each do |var|
if Hash === var
var.each { |key, val| bind_param key, val }
else
bind_param index, var
index += 1
end
end
end
# Binds value to the named (or positional) placeholder. If +param+ is a
# Fixnum, it is treated as an index for a positional placeholder.
# Otherwise it is used as the name of the placeholder to bind to.
#
# See also #bind_params.
def bind_param( param, value )
must_be_open!
reset! if active?
if Fixnum === param
case value
when Bignum then
@driver.bind_int64( @handle, param, value )
when Integer then
@driver.bind_int( @handle, param, value )
when Numeric then
@driver.bind_double( @handle, param, value.to_f )
when Blob then
@driver.bind_blob( @handle, param, value )
when nil then
@driver.bind_null( @handle, param )
else
@driver.bind_text( @handle, param, value )
end
else
param = param.to_s
param = ":#{param}" unless param[0] == ?:
index = @driver.bind_parameter_index( @handle, param )
raise Exception, "no such bind parameter '#{param}'" if index == 0
bind_param index, value
end
end
# Execute the statement. This creates a new ResultSet object for the
# statement's virtual machine. If a block was given, the new ResultSet will
# be yielded to it; otherwise, the ResultSet will be returned.
#
# Any parameters will be bound to the statement using #bind_params.
#
# Example:
#
# stmt = db.prepare( "select * from table" )
# stmt.execute do |result|
# ...
# end
#
# See also #bind_params, #execute!.
def execute( *bind_vars )
must_be_open!
reset! if active?
bind_params(*bind_vars) unless bind_vars.empty?
@results = ResultSet.new( @db, self )
if block_given?
yield @results
else
return @results
end
end
# Execute the statement. If no block was given, this returns an array of
# rows returned by executing the statement. Otherwise, each row will be
# yielded to the block.
#
# Any parameters will be bound to the statement using #bind_params.
#
# Example:
#
# stmt = db.prepare( "select * from table" )
# stmt.execute! do |row|
# ...
# end
#
# See also #bind_params, #execute.
def execute!( *bind_vars )
result = execute( *bind_vars )
rows = [] unless block_given?
while row = result.next
if block_given?
yield row
else
rows << row
end
end
rows
end
# Resets the statement. This is typically done internally, though it might
# occassionally be necessary to manually reset the statement.
def reset!(clear_result=true)
@driver.reset(@handle)
@results = nil if clear_result
end
# Returns true if the statement is currently active, meaning it has an
# open result set.
def active?
not @results.nil?
end
# Return an array of the column names for this statement. Note that this
# may execute the statement in order to obtain the metadata; this makes it
# a (potentially) expensive operation.
def columns
get_metadata unless @columns
return @columns
end
# Return an array of the data types for each column in this statement. Note
# that this may execute the statement in order to obtain the metadata; this
# makes it a (potentially) expensive operation.
def types
get_metadata unless @types
return @types
end
# A convenience method for obtaining the metadata about the query. Note
# that this will actually execute the SQL, which means it can be a
# (potentially) expensive operation.
def get_metadata
must_be_open!
@columns = []
@types = []
column_count = @driver.column_count( @handle )
column_count.times do |column|
@columns << @driver.column_name( @handle, column )
@types << @driver.column_decltype( @handle, column )
end
@columns.freeze
@types.freeze
end
private :get_metadata
# Performs a sanity check to ensure that the statement is not
# closed. If it is, an exception is raised.
def must_be_open! # :nodoc:
if @closed
raise SQLite3::Exception, "cannot use a closed statement"
end
end
end
end