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module DBI
#
# StatementHandles are used to encapsulate the process of managing a
# statement (DDL or DML) and its parameters, sending it to the database,
# and gathering any results from the execution of that statement.
#
# As with the other `Base` classes, the terms "DBD Required" and "DBD
# Optional" are defined in DBI::BaseDatabase.
#
class BaseStatement < Base
attr_accessor :raise_error
def initialize(attr=nil)
@attr = attr || {}
end
#
# Bind a parameter to the statement. DBD Required.
#
# The parameter number is numeric and indexes starting at 1. This
# corresponds to the question marks (?) in the statement from the
# left-most part of the statement moving forward.
#
# The value may be any ruby type. How these are handled is
# DBD-dependent, but the vast majority of DBDs will convert these to
# string inside the query.
#
def bind_param(param, value, attribs)
raise NotImplementedError
end
#
# Execute the statement with the known binds. DBD Required.
#
def execute
raise NotImplementedError
end
#
# Close the statement and any result cursors. DBD Required.
#
# Note:: Most implementations will fail miserably if you forget to
# finish your statement handles.
def finish
raise NotImplementedError
end
#
# Fetch the next row in the result set. DBD Required.
#
# DBI::Row is responsible for formatting the data the DBD provides it.
#
def fetch
raise NotImplementedError
end
##
# returns result-set column information as array
# of hashs, where each hash represents one column. See
# BaseDatabase#columns. DBD Required.
#
def column_info
raise NotImplementedError
end
#============================================
# OPTIONAL
#============================================
#
# Take a list of bind variables and bind them successively using bind_param.
#
def bind_params(*bindvars)
bindvars.each_with_index {|val,i| bind_param(i+1, val, nil) }
self
end
#
# Cancel any result cursors. DBD Optional, but intentionally does not
# raise any exception as it's used internally to maintain consistency.
#
def cancel
end
#
# fetch_scroll is provided with a direction and offset and works
# similar to how seek() is used on files.
#
# The constants available for direction are as follows:
#
# * SQL_FETCH_NEXT: fetch the next result.
# * SQL_FETCH_LAST: fetch the last result, period.
# * SQL_FETCH_RELATIVE: fetch the result at the offset.
#
# Other constants can be used, but if this method is not supplied by
# the driver, they will result in a raise of DBI::NotSupportedError.
#
def fetch_scroll(direction, offset)
case direction
when SQL_FETCH_NEXT
return fetch
when SQL_FETCH_LAST
last_row = nil
while (row=fetch) != nil
last_row = row
end
return last_row
when SQL_FETCH_RELATIVE
raise NotSupportedError if offset <= 0
row = nil
offset.times { row = fetch; break if row.nil? }
return row
else
raise NotSupportedError
end
end
#
# fetch x rows. The result is Array of DBI::Row.
#
def fetch_many(cnt)
rows = []
cnt.times do
row = fetch
break if row.nil?
rows << row.dup
end
if rows.empty?
nil
else
rows
end
end
#
# Fetch all available rows. Result is Array of DBI::Row.
#
def fetch_all
rows = []
loop do
row = fetch
break if row.nil?
rows << row.dup
end
if rows.empty?
nil
else
rows
end
end
#
# Get statement attributes.
#
def [](attr)
@attr ||= { }
@attr[attr]
end
#
# Set statement attributes. DBD Optional.
#
def []=(attr, value)
raise NotSupportedError
end
end # class BaseStatement
end
|
