The engine’s vocabulary, one term at a time

Concurrent commits written to the write-ahead log together, behind one persistence barrier per group. A write is acknowledged, and published to consumers, only after its group is durable.

A secondary index that keeps the smallest and largest value per region of data, so a range read skips regions that cannot match. Like every index, it changes how much data a read touches, never what it returns.

The engine’s one internal contract for publishing committed changes to every consumer that derives state from them. It has no SQL of its own; you use it through streaming queries, transformations and materialized views.

A named policy bound to a table that expires its rows by age.

The clause that decides which recording wins among versions at the same effective position. It is compared after the effective order, and the commit order breaks any remaining tie.

The state a continuous query keeps, shared by every subscriber of the same statement. When the last subscriber leaves, it stays ready for a configured time so a returning subscriber joins without reseeding.

On a federation consumer, the declaration that connects to a host instance with a stored credential and registers the host’s exposed tables as read-only external relations under local names.

A named policy bound to a table that tiers its data between local devices and object storage.

The per-table choice of physical layout: a row-oriented projection, a columnar projection, or both. Omitting the clause takes the node’s default.

A query that stays open. It sends one snapshot of its result, then exact changes to that result as new writes commit, over a WebSocket session.

What a subscriber selects changes by: a relation, a component of its stored state such as one attribute group, and a key. Never a stream name alone.

A consumer of the committed feed: a streaming query session, a transformation, a materialized view, an index, a projection or a cache, each with its own durable cursor.

The read-only relations the engine maintains about itself, read with an ordinary query or followed with a streaming one. Each read needs the permission the docs list for it.

A named, catalog-owned writer that keeps a table, or one attribute group of it, derived from other relations. It applies every committed change once, across restarts, until it is dropped.

The three windows a streaming query can open over a relation and a time: fixed, non-overlapping windows; overlapping windows that advance by a step; and windows closed by a gap in activity.

A principal created with a SQL statement, its password passed as a bound parameter so it never appears in statement text. A new user holds no permission until a role grants one.

A table that keeps one current row per primary key and retains every accepted version beside it, so you can read the table as it stood at a past commit.

The local, segmented, checksummed log a tablet’s commits go to before they are acknowledged. On restart a tablet replays the suffix written after its last checkpoint.