from .dispatch import dispatch

from .compatibility import basestring

from blaze.interactive import _Data

from blaze.interactive import data as bz_data

@dispatch(object, (basestring, list, tuple))

def create_index(t, column_name_or_names, name=None):

"""Create an index on a column.

Parameters

----------

o : table-like

index_name : str

The name of the index to create

column_name_or_names : string, list, tuple

A column name to index on, or a list or tuple for a composite index

Examples

--------

>>> # Using SQLite

>>> from blaze import SQL

>>> # create a table called 'tb', in memory

>>> sql = SQL('sqlite:///:memory:', 'tb',

... schema='{id: int64, value: float64, categ: string}')

>>> dta = [(1, 2.0, 'a'), (2, 3.0, 'b'), (3, 4.0, 'c')]

>>> sql.extend(dta)

>>> # create an index on the 'id' column (for SQL we must provide a name)

>>> sql.table.indexes

set()

>>> create_index(sql, 'id', name='id_index')

>>> sql.table.indexes

{Index('id_index', Column('id', BigInteger(), table=<tb>, nullable=False))}

"""

raise NotImplementedError("create_index not implemented for type %r" %

type(t).__name__)

@dispatch(_Data, (basestring, list, tuple))

def create_index(dta, column_name_or_names, name=None, **kwargs):

return create_index(dta.data, column_name_or_names, name=name, **kwargs)

@dispatch(basestring, (basestring, list, tuple))

def create_index(uri, column_name_or_names, name=None, **kwargs):

dta = bz_data(uri, **kwargs)

create_index(dta, column_name_or_names, name=name)

return dta