492d5d174a
### What changes were proposed in this pull request? docs/sql-ref-syntax-qry-select-usedb.md -> docs/sql-ref-syntax-ddl-usedb.md docs/sql-ref-syntax-aux-refresh-table.md -> docs/sql-ref-syntax-aux-cache-refresh-table.md ### Why are the changes needed? usedb belongs to DDL. Its location should be consistent with other DDL commands file locations similar reason for refresh table ### Does this PR introduce _any_ user-facing change? before change, when clicking USE DATABASE, the side bar menu shows select commands <img width="1200" alt="Screen Shot 2020-07-04 at 9 05 35 AM" src="https://user-images.githubusercontent.com/13592258/86516696-b45f8a80-bdd7-11ea-8dba-3a5cca22aad3.png"> after change, when clicking USE DATABASE, the side bar menu shows DDL commands <img width="1120" alt="Screen Shot 2020-07-04 at 9 06 06 AM" src="https://user-images.githubusercontent.com/13592258/86516703-bf1a1f80-bdd7-11ea-8a90-ae7eaaafd44c.png"> before change, when clicking refresh table, the side bar menu shows Auxiliary statements <img width="1200" alt="Screen Shot 2020-07-04 at 9 30 40 AM" src="https://user-images.githubusercontent.com/13592258/86516877-3d2af600-bdd9-11ea-9568-0a6f156f57da.png"> after change, when clicking refresh table, the side bar menu shows Cache statements <img width="1199" alt="Screen Shot 2020-07-04 at 9 35 21 AM" src="https://user-images.githubusercontent.com/13592258/86516937-b4f92080-bdd9-11ea-8ad1-5f5a7f58d76b.png"> ### How was this patch tested? Manually build and check Closes #28995 from huaxingao/docs_fix. Authored-by: Huaxin Gao <huaxing@us.ibm.com> Signed-off-by: Huaxin Gao <huaxing@us.ibm.com>
83 lines
2.7 KiB
Markdown
83 lines
2.7 KiB
Markdown
---
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layout: global
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title: CACHE TABLE
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displayTitle: CACHE TABLE
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license: |
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Licensed to the Apache Software Foundation (ASF) under one or more
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contributor license agreements. See the NOTICE file distributed with
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this work for additional information regarding copyright ownership.
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The ASF licenses this file to You under the Apache License, Version 2.0
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(the "License"); you may not use this file except in compliance with
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the License. You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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---
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### Description
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`CACHE TABLE` statement caches contents of a table or output of a query with the given storage level. If a query is cached, then a temp view will be created for this query.
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This reduces scanning of the original files in future queries.
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### Syntax
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```sql
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CACHE [ LAZY ] TABLE table_identifier
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[ OPTIONS ( 'storageLevel' [ = ] value ) ] [ [ AS ] query ]
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```
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### Parameters
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* **LAZY**
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Only cache the table when it is first used, instead of immediately.
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* **table_identifier**
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Specifies the table or view name to be cached. The table or view name may be optionally qualified with a database name.
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**Syntax:** `[ database_name. ] table_name`
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* **OPTIONS ( 'storageLevel' [ = ] value )**
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`OPTIONS` clause with `storageLevel` key and value pair. A Warning is issued when a key other than `storageLevel` is used. The valid options for `storageLevel` are:
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* `NONE`
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* `DISK_ONLY`
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* `DISK_ONLY_2`
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* `MEMORY_ONLY`
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* `MEMORY_ONLY_2`
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* `MEMORY_ONLY_SER`
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* `MEMORY_ONLY_SER_2`
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* `MEMORY_AND_DISK`
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* `MEMORY_AND_DISK_2`
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* `MEMORY_AND_DISK_SER`
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* `MEMORY_AND_DISK_SER_2`
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* `OFF_HEAP`
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An Exception is thrown when an invalid value is set for `storageLevel`. If `storageLevel` is not explicitly set using `OPTIONS` clause, the default `storageLevel` is set to `MEMORY_AND_DISK`.
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* **query**
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A query that produces the rows to be cached. It can be in one of following formats:
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* a `SELECT` statement
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* a `TABLE` statement
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* a `FROM` statement
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### Examples
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```sql
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CACHE TABLE testCache OPTIONS ('storageLevel' 'DISK_ONLY') SELECT * FROM testData;
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```
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### Related Statements
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* [CLEAR CACHE](sql-ref-syntax-aux-cache-clear-cache.html)
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* [UNCACHE TABLE](sql-ref-syntax-aux-cache-uncache-table.html)
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* [REFRESH TABLE](sql-ref-syntax-aux-cache-refresh-table.html)
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* [REFRESH](sql-ref-syntax-aux-cache-refresh.html)
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