paul-rogers commented on a change in pull request #1953: Add docs for Drill
Metastore
URL: https://github.com/apache/drill/pull/1953#discussion_r366681625
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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
+
+The ANALYZE TABLE REFRESH METADATA statement supports the following syntax:
+
+ ANALYZE TABLE [table_name] [COLUMNS {(col1, col2, ...) | NONE}]
+ REFRESH METADATA ['level' LEVEL]
+ [{COMPUTE | ESTIMATE} | STATISTICS [(column1, column2, ...)]
+ [ SAMPLE number PERCENT ]]
+
+## Parameters
+
+*table_name*
+The name of the table or directory for which Drill will collect table
metadata. If the table does not exist, or the table
+ is temporary, the command fails and metadata is not collected and stored.
+
+*COLUMNS (col1, col2, ...)*
+Optional names of the column(s) for which Drill will generate and store
metadata. the Stored schema will include all table columns.
+
+*COLUMNS NONE*
+Specifies to ignore collecting and storing metadata for all table columns.
+
+*level*
+Optional varchar literal which specifies maximum level depth for collecting
metadata.
Review comment:
varchar --> VARCHAR
(Since this is a quoted string, can we make it user friendly? "ROW_GROUP"
--> "ROW GROUP" (no underscore.) Actually, why can't this be a keyword?
Please define the terms, especially `SEGMENT`. Also, what is the advantage
of one level vs. another?)
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