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Maxim Gekk 3d85c54895 [SPARK-28700][SQL] Use DECIMAL type for sec in make_timestamp() 
## What changes were proposed in this pull request?

Changed type of `sec` argument in the `make_timestamp()` function from `DOUBLE` to `DECIMAL(8, 6)`. The scale is set to 6 to cover microsecond fractions, and the precision is 2 digits for seconds + 6 digits for microsecond fraction. New type prevents losing precision in some cases, for example:

Before:
```sql
spark-sql> select make_timestamp(2019, 8, 12, 0, 0, 58.000001);
2019-08-12 00:00:58
```

After:
```sql
spark-sql> select make_timestamp(2019, 8, 12, 0, 0, 58.000001);
2019-08-12 00:00:58.000001
```

Also switching to `DECIMAL` fixes rounding `sec` towards "nearest neighbor" unless both neighbors are equidistant, in which case round up. For example:

Before:
```sql
spark-sql> select make_timestamp(2019, 8, 12, 0, 0, 0.1234567);
2019-08-12 00:00:00.123456
```

After:
```sql
spark-sql> select make_timestamp(2019, 8, 12, 0, 0, 0.1234567);
2019-08-12 00:00:00.123457
```

## How was this patch tested?

This was tested by `DateExpressionsSuite` and `pgSQL/timestamp.sql`.

Closes #25421 from MaxGekk/make_timestamp-decimal.

Authored-by: Maxim Gekk <max.gekk@gmail.com>
Signed-off-by: Dongjoon Hyun <dhyun@apple.com>
2019-08-13 15:51:50 -07:00
..
catalyst [SPARK-28700][SQL] Use DECIMAL type for sec in make_timestamp() 2019-08-13 15:51:50 -07:00
core [SPARK-28700][SQL] Use DECIMAL type for sec in make_timestamp() 2019-08-13 15:51:50 -07:00
hive [SPARK-28708][SQL] IsolatedClientLoader will not load hive classes from application jars on JDK9+ 2019-08-13 11:21:19 -07:00
hive-thriftserver [SPARK-28714][SQL][TEST] Add hive.aux.jars.path test for spark-sql shell 2019-08-13 09:19:58 -07:00
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 [SPARK-28473][DOC] Stylistic consistency of build command in README 2019-07-23 16:29:46 -07:00

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.