paul-rogers commented on a change in pull request #1953: Add docs for Drill
Metastore
URL: https://github.com/apache/drill/pull/1953#discussion_r366679074
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File path:
_docs/sql-reference/sql-commands/007-analyze-table-refresh-metadata.md
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@@ -0,0 +1,158 @@
+---
+title: "ANALYZE TABLE REFRESH METADATA"
+parent: "SQL Commands"
+date: 2020-01-13
+---
+
+Starting from Drill 1.17, you can store table metadata (including schema and
computed statistics) into Drill Metastore.
+This metadata will be used when querying a table for more optimal plan
creation.
+
+{% include startnote.html %}In Drill 1.17, this feature is supported for
Parquet tables only and is disabled by default.{% include endnote.html %}
+
+To enable Drill Metastore usage, the following option `metastore.enabled`
should be set to `true`, as shown:
+
+ SET `metastore.enabled` = true;
+
+Alternatively, you can enable the option in the Drill Web UI at
`http://<drill-hostname-or-ip-address>:8047/options`.
+
+## Syntax
Review comment:
(We just told the user that a metastore exists and how to enable it. Now we
tell them the syntax of commands. We need a transition.)
Once you enable the Metastore, the next step is to populate it with data.
Drill can query a table whether that table has a Metastore entry or not. (If
you are familiar with Hive, then you know that Hive requires that all tables
have Hive Metastore entries before you can query them.) In Drill, only add data
to the Metastore when doing so improves query performance. In general, large
tables benefit from statistics more than small tables do.
Unlike Hive, Drill does not require you to declare a schema. Instead, Drill
infers the schema by scanning your table. Drill not only infers the schema, it
optionally computes statistics about your table.
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