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Maxim Gekk ab8710b579 [SPARK-27423][SQL] Cast DATE <-> TIMESTAMP according to the SQL standard 
## What changes were proposed in this pull request?

According to SQL standard, value of `DATE` type is union of year, month, dayInMonth, and it is independent from any time zones. To convert it to Catalyst's `TIMESTAMP`, `DATE` value should be "extended" by the time at midnight - `00:00:00`. The resulted local date+time should be considered as a timestamp in the session time zone, and casted to microseconds since epoch in `UTC` accordingly.

The reverse casting from `TIMESTAMP` to `DATE` should be performed in the similar way. `TIMESTAMP` values should be represented as a local date+time in the session time zone. And the time component should be just removed. For example, `TIMESTAMP 2019-04-10 00:10:12` -> `DATE 2019-04-10`. The resulted date is converted to days since epoch `1970-01-01`.

## How was this patch tested?

The changes were tested by existing test suites - `DateFunctionsSuite`, `DateExpressionsSuite` and `CastSuite`.

Closes #24332 from MaxGekk/cast-timestamp-to-date2.

Lead-authored-by: Maxim Gekk <maxim.gekk@databricks.com>
Co-authored-by: Maxim Gekk <max.gekk@gmail.com>
Signed-off-by: Wenchen Fan <wenchen@databricks.com>
2019-04-10 22:41:19 +08:00
..
catalyst [SPARK-27423][SQL] Cast DATE <-> TIMESTAMP according to the SQL standard 2019-04-10 22:41:19 +08:00
core [SPARK-27422][SQL] current_date() should return current date in the session time zone 2019-04-10 21:54:50 +08:00
hive [SPARK-27271][SQL] Migrate Text to File Data Source V2 2019-04-08 10:15:22 -07:00
hive-thriftserver [SPARK-26992][STS] Fix STS scheduler pool correct delivery 2019-04-06 17:14:29 -05:00
create-docs.sh [MINOR][DOCS] Minor doc fixes related with doc build and uses script dir in SQL doc gen script 2017-08-26 13:56:24 +09:00
gen-sql-markdown.py [SPARK-27328][SQL] Add 'deprecated' in ExpressionDescription for extended usage and SQL doc 2019-04-09 13:49:42 +08:00
mkdocs.yml [SPARK-21485][SQL][DOCS] Spark SQL documentation generation for built-in functions 2017-07-26 09:38:51 -07:00
README.md [MINOR][DOC] Fix some typos and grammar issues 2018-04-06 13:37:08 +08:00

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 an extension of SQLContext called HiveContext that allows 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.