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Clarify need for exchange manager configuration #18029

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Jun 27, 2023
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Clarify need for exchange manager configuration #18029

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14 changes: 7 additions & 7 deletions docs/src/main/sphinx/admin/fault-tolerant-execution.rst
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Expand Up @@ -98,8 +98,7 @@ QUERY
A ``QUERY`` retry policy instructs Trino to automatically retry a query in the
event of an error occuring on a worker node. A ``QUERY`` retry policy is
recommended when the majority of the Trino cluster's workload consists of many
small queries, or if an :ref:`exchange manager <fte-exchange-manager>` is not
configured.
small queries.

By default Trino does not implement fault tolerance for queries whose result set
exceeds 32MB in size, such as :doc:`/sql/select` statements that return a very
Expand All @@ -116,11 +115,12 @@ therefore allows for storage of spilled data beyond the in-memory buffer size.
TASK
^^^^

A ``TASK`` retry policy instructs Trino to retry individual query
:ref:`tasks <trino-concept-task>` in the event of failure. This policy is
recommended when executing large batch queries, as the cluster can more
efficiently retry smaller tasks within the query rather than retry the whole
query.
A ``TASK`` retry policy instructs Trino to retry individual query :ref:`tasks
<trino-concept-task>` in the event of failure. You must configure an
:ref:`exchange manager <fte-exchange-manager>` to use the task retry policy.
This policy is recommended when executing large batch queries, as the cluster
can more efficiently retry smaller tasks within the query rather than retry the
whole query.

When a cluster is configured with a ``TASK`` retry policy, some relevant
configuration properties have their default values changed to follow best
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