paul-rogers commented on a change in pull request #1953: Add docs for Drill
Metastore
URL: https://github.com/apache/drill/pull/1953#discussion_r366680438
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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.
Review comment:
(Not clear here. If this command infers schema, do I specify here the only
columns that Drill should infer? Does Drill then not store schema information
for the other columns?
Or, is this the list of columns for which Drill will gather statistics?
Maybe Drill infers schema for all columns?)
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