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gengjiaan 1686cff9a1 [SPARK-36037][SQL] Support ANSI SQL LOCALTIMESTAMP datetime value function 
### What changes were proposed in this pull request?
`LOCALTIMESTAMP()` is a datetime value function from ANSI SQL.
The syntax show below:
```
<datetime value function> ::=
    <current date value function>
  | <current time value function>
  | <current timestamp value function>
  | <current local time value function>
  | <current local timestamp value function>
<current date value function> ::=
CURRENT_DATE
<current time value function> ::=
CURRENT_TIME [ <left paren> <time precision> <right paren> ]
<current local time value function> ::=
LOCALTIME [ <left paren> <time precision> <right paren> ]
<current timestamp value function> ::=
CURRENT_TIMESTAMP [ <left paren> <timestamp precision> <right paren> ]
<current local timestamp value function> ::=
LOCALTIMESTAMP [ <left paren> <timestamp precision> <right paren> ]
```

`LOCALTIMESTAMP()` returns the current timestamp at the start of query evaluation as TIMESTAMP WITH OUT TIME ZONE. This is similar to `CURRENT_TIMESTAMP()`.
Note we need to update the optimization rule `ComputeCurrentTime` so that Spark returns the same result in a single query if the function is called multiple times.

### Why are the changes needed?
`CURRENT_TIMESTAMP()` returns the current timestamp at the start of query evaluation.
`LOCALTIMESTAMP()` returns the current timestamp without time zone at the start of query evaluation.
The `LOCALTIMESTAMP` function is an ANSI SQL.
The `LOCALTIMESTAMP` function is very useful.

### Does this PR introduce _any_ user-facing change?
'Yes'. Support new function `LOCALTIMESTAMP()`.

### How was this patch tested?
New tests.

Closes #33258 from beliefer/SPARK-36037.

Lead-authored-by: gengjiaan <gengjiaan@360.cn>
Co-authored-by: Jiaan Geng <beliefer@163.com>
Co-authored-by: Wenchen Fan <cloud0fan@gmail.com>
Signed-off-by: Wenchen Fan <wenchen@databricks.com>
(cherry picked from commit b4f7758944)
Signed-off-by: Wenchen Fan <wenchen@databricks.com>
2021-07-14 15:39:02 +08:00
..
catalyst [SPARK-36037][SQL] Support ANSI SQL LOCALTIMESTAMP datetime value function 2021-07-14 15:39:02 +08:00
core [SPARK-36037][SQL] Support ANSI SQL LOCALTIMESTAMP datetime value function 2021-07-14 15:39:02 +08:00
hive [SPARK-36012][SQL] Add null flag in SHOW CREATE TABLE 2021-07-09 01:21:57 +08:00
hive-thriftserver [SPARK-35749][SPARK-35773][SQL] Parse unit list interval literals as tightest year-month/day-time interval types 2021-07-13 18:55:22 +08:00
create-docs.sh [SPARK-34010][SQL][DODCS] Use python3 instead of python in SQL documentation build 2021-01-05 19:48:10 +09:00
gen-sql-api-docs.py [SPARK-34747][SQL][DOCS] Add virtual operators to the built-in function document 2021-03-19 10:19:26 +09:00
gen-sql-config-docs.py [SPARK-32194][PYTHON] Use proper exception classes instead of plain Exception 2021-05-26 11:54:40 +09:00
gen-sql-functions-docs.py
mkdocs.yml
README.md

README.md

Spark SQL

This module provides support for executing relational queries expressed in either SQL or the DataFrame/Dataset API.

Spark SQL is broken up into four subprojects:

  • Catalyst (sql/catalyst) - An implementation-agnostic framework for manipulating trees of relational operators and expressions.
  • Execution (sql/core) - A query planner / execution engine for translating Catalyst's logical query plans into Spark RDDs. This component also includes a new public interface, SQLContext, that allows users to execute SQL or LINQ statements against existing RDDs and Parquet files.
  • Hive Support (sql/hive) - Includes extensions that allow users to write queries using a subset of HiveQL and access data from a Hive Metastore using Hive SerDes. There are also wrappers that allow users to run queries that include Hive UDFs, UDAFs, and UDTFs.
  • HiveServer and CLI support (sql/hive-thriftserver) - Includes support for the SQL CLI (bin/spark-sql) and a HiveServer2 (for JDBC/ODBC) compatible server.

Running ./sql/create-docs.sh generates SQL documentation for built-in functions under sql/site, and SQL configuration documentation that gets included as part of configuration.md in the main docs directory.