cassandra.metadata - Schema and Ring Topology¶

Schemas¶

class cassandra.metadata.KeyspaceMetadata¶

A representation of the schema for a single keyspace.

virtual = False¶

A boolean indicating if this is a virtual keyspace or not. Always False for clusters running Cassandra pre-4.0 and DSE pre-6.7 versions.

Added in version 3.15.

name = None¶

The string name of the keyspace.

durable_writes = True¶

A boolean indicating whether durable writes are enabled for this keyspace or not.

replication_strategy = None¶

A ReplicationStrategy subclass object.

tables = None¶

A map from table names to instances of TableMetadata.

indexes = None¶

A dict mapping index names to IndexMetadata instances.

user_types = None¶

A map from user-defined type names to instances of UserType.

Added in version 2.1.0.

functions = None¶

A map from user-defined function signatures to instances of Function.

Added in version 2.6.0.

aggregates = None¶

A map from user-defined aggregate signatures to instances of Aggregate.

Added in version 2.6.0.

views = None¶

A dict mapping view names to MaterializedViewMetadata instances.

graph_engine = None¶

A string indicating whether a graph engine is enabled for this keyspace (Core/Classic).

export_as_string()¶

Returns a CQL query string that can be used to recreate the entire keyspace, including user-defined types and tables.

as_cql_query()¶

Returns a CQL query string that can be used to recreate just this keyspace, not including user-defined types and tables.

class cassandra.metadata.UserType¶

A user defined type, as created by CREATE TYPE statements.

User-defined types were introduced in Cassandra 2.1.

Added in version 2.1.0.

keyspace = None¶

The string name of the keyspace in which this type is defined.

name = None¶

The name of this type.

field_names = None¶

An ordered list of the names for each field in this user-defined type.

field_types = None¶

An ordered list of the types for each field in this user-defined type.

as_cql_query(formatted=False)¶

Returns a CQL query that can be used to recreate this type. If formatted is set to True, extra whitespace will be added to make the query more readable.

class cassandra.metadata.Function¶

A user defined function, as created by CREATE FUNCTION statements.

User-defined functions were introduced in Cassandra 2.2

Added in version 2.6.0.

keyspace = None¶

The string name of the keyspace in which this function is defined

name = None¶

The name of this function

argument_types = None¶

An ordered list of the types for each argument to the function

argument_names = None¶

An ordered list of the names of each argument to the function

return_type = None¶

Return type of the function

language = None¶

Language of the function body

body = None¶

Function body string

called_on_null_input = None¶

Flag indicating whether this function should be called for rows with null values (convenience function to avoid handling nulls explicitly if the result will just be null)

deterministic = None¶

Flag indicating if this function is guaranteed to produce the same result for a particular input. This is available only for DSE >=6.0.

monotonic = None¶

Flag indicating if this function is guaranteed to increase or decrease monotonically on any of its arguments. This is available only for DSE >=6.0.

monotonic_on = None¶

A list containing the argument or arguments over which this function is monotonic. This is available only for DSE >=6.0.

as_cql_query(formatted=False)¶

Returns a CQL query that can be used to recreate this function. If formatted is set to True, extra whitespace will be added to make the query more readable.

class cassandra.metadata.Aggregate¶

A user defined aggregate function, as created by CREATE AGGREGATE statements.

Aggregate functions were introduced in Cassandra 2.2

Added in version 2.6.0.

keyspace = None¶

The string name of the keyspace in which this aggregate is defined

name = None¶

The name of this aggregate

argument_types = None¶

An ordered list of the types for each argument to the aggregate

state_func = None¶

Name of a state function

state_type = None¶

Type of the aggregate state

final_func = None¶

Name of a final function

initial_condition = None¶

Initial condition of the aggregate

return_type = None¶

Return type of the aggregate

deterministic = None¶

Flag indicating if this function is guaranteed to produce the same result for a particular input and state. This is available only with DSE >=6.0.

as_cql_query(formatted=False)¶

Returns a CQL query that can be used to recreate this aggregate. If formatted is set to True, extra whitespace will be added to make the query more readable.

class cassandra.metadata.TableMetadata¶

A representation of the schema for a single table.

property primary_key¶

A list of ColumnMetadata representing the components of the primary key for this table.

property is_cql_compatible¶

A boolean indicating if this table can be represented as CQL in export

extensions = None¶

Metadata describing configuration for table extensions

keyspace_name = None¶

String name of this Table’s keyspace

name = None¶

The string name of the table.

partition_key = None¶

A list of ColumnMetadata instances representing the columns in the partition key for this table. This will always hold at least one column.

clustering_key = None¶

A list of ColumnMetadata instances representing the columns in the clustering key for this table. These are all of the primary_key columns that are not in the partition_key.

Note that a table may have no clustering keys, in which case this will be an empty list.

columns = None¶

A dict mapping column names to ColumnMetadata instances.

indexes = None¶

A dict mapping index names to IndexMetadata instances.

options = None¶

A dict mapping table option names to their specific settings for this table.

triggers = None¶

A dict mapping trigger names to TriggerMetadata instances.

views = None¶

A dict mapping view names to MaterializedViewMetadata instances.

virtual = False¶

A boolean indicating if this is a virtual table or not. Always False for clusters running Cassandra pre-4.0 and DSE pre-6.7 versions.

Added in version 3.15.

export_as_string()¶

Returns a string of CQL queries that can be used to recreate this table along with all indexes on it. The returned string is formatted to be human readable.

as_cql_query(formatted=False)¶

Returns a CQL query that can be used to recreate this table (index creations are not included). If formatted is set to True, extra whitespace will be added to make the query human readable.

class cassandra.metadata.TableMetadataV3¶

For C* 3.0+. option_maps take a superset of map names, so if nothing changes structurally, new option maps can just be appended to the list.

property is_cql_compatible¶

A boolean indicating if this table can be represented as CQL in export

class cassandra.metadata.TableMetadataDSE68¶

vertex = None¶

A VertexMetadata instance, if graph enabled

edge = None¶

A EdgeMetadata instance, if graph enabled

as_cql_query(formatted=False)¶

Returns a CQL query that can be used to recreate this table (index creations are not included). If formatted is set to True, extra whitespace will be added to make the query human readable.

class cassandra.metadata.ColumnMetadata¶

A representation of a single column in a table.

table = None¶

The TableMetadata this column belongs to.

name = None¶

The string name of this column.

cql_type = None¶

The CQL type for the column.

is_static = False¶

If this column is static (available in Cassandra 2.1+), this will be True, otherwise False.

is_reversed = False¶

If this column is reversed (DESC) as in clustering order

class cassandra.metadata.IndexMetadata¶

A representation of a secondary index on a column.

keyspace_name = None¶

A string name of the keyspace.

table_name = None¶

A string name of the table this index is on.

name = None¶

A string name for the index.

kind = None¶

A string representing the kind of index (COMPOSITE, CUSTOM,…).

index_options = {}¶

A dict of index options.

as_cql_query()¶

Returns a CQL query that can be used to recreate this index.

export_as_string()¶

Returns a CQL query string that can be used to recreate this index.

class cassandra.metadata.MaterializedViewMetadata¶

A representation of a materialized view on a table

extensions = None¶

Metadata describing configuration for table extensions

keyspace_name = None¶

A string name of the keyspace of this view.

name = None¶

A string name of the view.

base_table_name = None¶

A string name of the base table for this view.

partition_key = None¶

A list of ColumnMetadata instances representing the columns in the partition key for this view. This will always hold at least one column.

clustering_key = None¶

A list of ColumnMetadata instances representing the columns in the clustering key for this view.

Note that a table may have no clustering keys, in which case this will be an empty list.

columns = None¶

A dict mapping column names to ColumnMetadata instances.

include_all_columns = None¶

A flag indicating whether the view was created AS SELECT *

where_clause = None¶

String WHERE clause for the view select statement. From server metadata

options = None¶

A dict mapping table option names to their specific settings for this view.

as_cql_query(formatted=False)¶

Returns a CQL query that can be used to recreate this function. If formatted is set to True, extra whitespace will be added to make the query more readable.

class cassandra.metadata.VertexMetadata¶

A representation of a vertex on a table

keyspace_name = None¶

A string name of the keyspace.

table_name = None¶

A string name of the table this vertex is on.

label_name = None¶

A string name of the label of this vertex.

class cassandra.metadata.EdgeMetadata¶

A representation of an edge on a table

keyspace_name = None¶

A string name of the keyspace

table_name = None¶

A string name of the table this edge is on

label_name = None¶

A string name of the label of this edge

from_table = None¶

A string name of the from table of this edge (incoming vertex)

from_label = None¶

A string name of the from table label of this edge (incoming vertex)

from_partition_key_columns = None¶

The columns that match the partition key of the incoming vertex table.

from_clustering_columns = None¶

The columns that match the clustering columns of the incoming vertex table.

to_table = None¶

A string name of the to table of this edge (outgoing vertex)

to_label = None¶

A string name of the to table label of this edge (outgoing vertex)

to_partition_key_columns = None¶

The columns that match the partition key of the outgoing vertex table.

to_clustering_columns = None¶

The columns that match the clustering columns of the outgoing vertex table.

Tokens and Ring Topology¶

class cassandra.metadata.TokenMap¶

Information about the layout of the ring.

token_class = None¶

A subclass of Token, depending on what partitioner the cluster uses.

ring = None¶

An ordered list of Token instances in the ring.

token_to_host_owner = None¶

A map of Token objects to the Host that owns that token.

tokens_to_hosts_by_ks = None¶

A map of keyspace names to a nested map of Token objects to sets of Host objects.

get_replicas(keyspace, token)¶

Get a set of Host instances representing all of the replica nodes for a given Token.

class cassandra.metadata.Token¶

Abstract class representing a token.

class cassandra.metadata.Murmur3Token(token)¶

A token for Murmur3Partitioner.

token is an int or string representing the token.

class cassandra.metadata.MD5Token(token)¶

A token for RandomPartitioner.

class cassandra.metadata.BytesToken(token)¶

A token for ByteOrderedPartitioner.

classmethod from_string(token_string)¶

token_string should be the string representation from the server.

cassandra.metadata.ReplicationStrategy¶

alias of _ReplicationStrategy

class cassandra.metadata.ReplicationFactor(all_replicas, transient_replicas=None)¶

Represent the replication factor of a keyspace.

all_replicas = None¶

The number of total replicas.

transient_replicas = None¶

The number of transient replicas.

Only set if the keyspace has transient replication enabled.

full_replicas = None¶

The number of replicas that own a full copy of the data. This is the same than all_replicas when transient replication is not enabled.

class cassandra.metadata.SimpleStrategy(options_map)¶

property replication_factor¶

The replication factor for this keyspace.

For backward compatibility, this returns the cassandra.metadata.ReplicationFactor.full_replicas value of cassandra.metadata.SimpleStrategy.replication_factor_info.

replication_factor_info = None¶

A cassandra.metadata.ReplicationFactor instance.

export_for_schema()¶

Returns a string version of these replication options which are suitable for use in a CREATE KEYSPACE statement.

class cassandra.metadata.NetworkTopologyStrategy(dc_replication_factors)¶

dc_replication_factors_info = None¶

A map of datacenter names to the cassandra.metadata.ReplicationFactor instance for that DC.

dc_replication_factors = None¶

A map of datacenter names to the replication factor for that DC.

For backward compatibility, this maps to the cassandra.metadata.ReplicationFactor.full_replicas value of the cassandra.metadata.NetworkTopologyStrategy.dc_replication_factors_info dict.

export_for_schema()¶

Returns a string version of these replication options which are suitable for use in a CREATE KEYSPACE statement.

class cassandra.metadata.LocalStrategy(options_map)¶

export_for_schema()¶

Returns a string version of these replication options which are suitable for use in a CREATE KEYSPACE statement.

cassandra.metadata.group_keys_by_replica(session, keyspace, table, keys)¶

Returns a dict with the keys grouped per host. This can be used to more accurately group by IN clause or to batch the keys per host.

If a valid replica is not found for a particular key it will be grouped under NO_VALID_REPLICA

Example usage:

>>> result = group_keys_by_replica(
...     session, "system", "peers",
...     (("127.0.0.1", ), ("127.0.0.2", )))