drill-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From GitBox <...@apache.org>
Subject [GitHub] [drill] paul-rogers commented on a change in pull request #1953: Add docs for Drill Metastore
Date Tue, 04 Feb 2020 03:12:26 GMT
paul-rogers commented on a change in pull request #1953: Add docs for Drill Metastore
URL: https://github.com/apache/drill/pull/1953#discussion_r374431849
 
 

 ##########
 File path: _docs/performance-tuning/drill-metastore/010-using-drill-metastore.md
 ##########
 @@ -0,0 +1,408 @@
+---
+title: "Using Drill Metastore"
+parent: "Drill Metastore"
+date: 2020-01-31
+---
+
+Drill 1.17 introduces the Drill Metastore which stores the table schema and table statistics.
Statistics allow Drill to better create optimal query plans.
+
+The Metastore is a Beta feature; it is subject to change. We encourage you to try it and
provide feedback.
+Because the Metastore is in Beta, the SQL commands and Metastore formats may change in the
next release.
+{% include startnote.html %}In Drill 1.17, this feature is supported for Parquet tables only
and is disabled by default.{% include endnote.html %}
+
+## Enabling Drill Metastore
+
+To use the Drill Metastore, you must enable it at the session or system level with one of
the following commands:
+
+	SET `metastore.enabled` = true;
+	ALTER SYSTEM SET `metastore.enabled` = true;
+
+Alternatively, you can enable the option in the Drill Web UI at `http://<drill-hostname-or-ip-address>:8047/options`.
+
+## Computing and storing table metadata to Drill Metastore
+
+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 
+ in the same way as it is done during regular select and computes some metadata like `MIN`
/ `MAX` column values and
+ `NULLS_COUNT` designated as "metadata" to be able to produce more optimizations like filter
push-down, etc. If
+ `planner.statistics.use` option is enabled, this command will also calculate and store table
statistics into Drill
+ Metastore.
+
+## Configuration
+
+Default Metastore configuration is defined in `drill-metastore-default.conf` file.
 
 Review comment:
   in *the*

----------------------------------------------------------------
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
 
For queries about this service, please contact Infrastructure at:
users@infra.apache.org


With regards,
Apache Git Services

Mime
View raw message