Cluster: A cluster consists of one or more nodes which share a cluster configuration. The cluster also defines how data is replicated and how internode communication is coordinated. Pilosa does not have a leader node, all data is evenly distributed, and any node can respond to queries.
Field: Fields are used to group rows into different categories. Row IDs are namespaced by field such that the same row ID in a different field refers to a different row. For ranked fields, rows are kept in sorted order within the field. Fields are one of five types: set, int, bool, time, and mutex. For more information, see data model and Creating fields.
Frame: Prior to Pilosa 1.0, fields were known as frames.
Gossip: A protocol used by Pilosa for internal communication.
GroupBy: A PQL query, with functionality similar to a SQL
GROUP BY clause, that returns the count of the intersection of every combination of rows taking one row each from the specified
Rows calls. GroupBy can be thought of as a multi-dimensional version of the TopN query.
Index: An Index is a top level container in Pilosa, analogous to a database in an RDBMS. Basic queries cannot operate across multiple indexes.
Jump Consistent Hash: A fast, minimal memory, consistent hash algorithm that evenly distributes the workload even when the number of buckets changes.
MaxShard: The total number of shards allocated to handle the current set of columns. This value is important for all nodes to efficiently distribute queries. MaxShard is zero-indexed, so if an index contains six shards, its MaxShard will be 5.
Node: An individual running instance of Pilosa server which belongs to a cluster.
Partition: The consistent hash maps keys to partitions (or locations on the unit circle), based on a preset maximum number of partitions. Partitions are then evenly mapped to physical nodes. To add nodes to the cluster, the partitions must be remapped, and data is then associated across the new cluster topology.
DefaultPartitionN is 256. It can be modified, but only at compile time, and before ingesting any data.
PQL: Pilosa Query Language.
Protobuf: Protocol Buffers is a binary serialization format which Pilosa uses for internal messages, and can be used by clients as an alternative to JSON.
Replica: A copy of a fragment on a different node than the original. The
cluster.replicas configuration parameter determines how many replicas of a fragment exist in the cluster. This includes the original, so a value of 1 means no extra copies are made.
Rows: A PQL query that returns a list of row IDs in the given field which have at least one bit set. The field argument is mandatory, the others are optional.
Rows is the primary argument used with the GroupBy query.
Slice: Prior to Pilosa 1.0, shards were known as slices.
View: Views separate the different data layouts within a Field. The primary view is standard, which represents the typical row/column data. Time based field views are automatically generated for each time quantum. Views are internally managed by Pilosa, and never exposed directly via the API. This simplifies the functional interface by separating it from the physical data representation.