Module mz_join_core_v2

A fork of DD’s JoinCore::join_core.

Currently, compute rendering knows three implementations for linear joins:

• Differential’s JoinCore::join_core
• A Materialize fork thereof, called mz_join_core
• Another Materialize fork thereof, called mz_join_core_v2

mz_join_core exists to solve a responsiveness problem with the DD implementation. DD’s join is only able to yield between keys. When computing a large cross-join or a highly skewed join, this can result in loss of interactivity when the join operator refuses to yield control for multiple seconds or longer, which in turn causes degraded user experience.

mz_join_core resolves the yielding issue but compromises by being quadratic over the number of distinct times in the input. mz_join_core_v2 is an attempt to replace the quadratic behavior by using a linear scan through times, copied from the DD implementation.

For the moment, we keep all three implementations around, selectable through feature flags. Eventually, we hope that mz_join_core_v2 proves itself sufficiently to become the only join implementation.

Structs

EditList 🔒

An accumulation of (value, time, diff) updates.

Joiner 🔒

Type that knows how to perform the core join logic.

ValueHistory 🔒

A history for replaying updates in time order.

Work 🔒

Work collected by the join operator.

Functions

mz_join_core 🔒

Joins two arranged collections with the same key type.