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module DBI
# Provides the core-level functionality for DatabaseHandles.
#
# If the method description says "DBD Required", it's the DBD's
# responsibility to create this method.
#
# Required methods unimplemented by the DBD will raise
# DBD::NotImplementedError.
#
# "DBD Optional" methods are methods that do not have a default
# implementation but are optional due to the fact that many databases may
# not support these features (and emulating them would be prohibitive).
#
# These methods raise DBI::NotSupportedError.
#
# Otherwise, DBI will provide a general alternative which should meet the
# expectations of the documentation. However, DBDs can override every
# method in this class.
#
class BaseDatabase < Base
def initialize(handle, attr)
@handle = handle
@attr = {}
attr.each {|k,v| self[k] = v}
end
# Disconnect from the database. DBD Required.
def disconnect
raise NotImplementedError
end
# Ping the database to ensure the connection is still alive. Boolean
# return, true for success. DBD Required.
def ping
raise NotImplementedError
end
# Prepare a cached statement, returning a StatementHandle. DBD
# Required.
def prepare(statement)
raise NotImplementedError
end
#
# Return a map of the columns that exist in the provided table name.
# DBD Required.
#
# The result should be an array of DBI::ColumnInfo objects which have,
# at minimum, the following fields:
#
# * name:: the name of the column.
# * type:: This is not a field name in itself. You have two options:
# * type_name:: The name of the type as returned by the database
# * dbi_type:: A DBI::Type-conforming class that can be used to convert to a native type.
# * precision:: the precision (generally length) of the column
# * scale:: the scale (generally a secondary attribute to precision
# that helps indicate length) of the column
#
def columns(table)
raise NotImplementedError
end
#============================================
# OPTIONAL
#============================================
# Schedule a commit to the database immediately. DBD Optional.
def commit
raise NotSupportedError
end
# Schedule a rollback to the database immediately. DBD Optional.
def rollback
raise NotSupportedError
end
# Return the tables available to the database connection.
#
# Note:: the basic implementation returns an empty array.
def tables
[]
end
#
# Execute a statement with the binds provided. Returns the statement
# handle unfinished.
#
# This is roughly equivalent to:
#
# sth = dbh.prepare("my statement")
# sth.execute(my, bind, vars)
#
def execute(statement, *bindvars)
stmt = prepare(statement)
stmt.bind_params(*bindvars)
stmt.execute
stmt
end
#
# Execute and complete the statement with the binds provided. Returns
# the row modified count (via BaseStatement#rows). Finishes the
# statement handle for you.
#
# Roughly equivalent to:
#
# sth = dbh.prepare("my statement")
# sth.execute(my, bind, vars)
# result = sth.rows
# sth.finish
#
# Returning the value stored in `result`.
def do(statement, *bindvars)
stmt = execute(statement, *bindvars)
res = stmt.rows
stmt.finish
return res
end
#
# Get an attribute from the DatabaseHandle. These are DBD specific and
# embody things like Auto-Commit support for transactional databases.
#
# DBD Authors:: This messes with @attr directly.
#
def [](attr)
@attr[attr]
end
# Set an attribute on the DatabaseHandle. DBD Optional.
def []=(attr, value)
raise NotSupportedError
end
end # class BaseDatabase
end
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