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Maxim Gekk 46fe40838a [SPARK-25669][SQL] Check CSV header only when it exists 
## What changes were proposed in this pull request?

Currently the first row of dataset of CSV strings is compared to field names of user specified or inferred schema independently of presence of CSV header. It causes false-positive error messages. For example, parsing `"1,2"` outputs the error:

```java
java.lang.IllegalArgumentException: CSV header does not conform to the schema.
 Header: 1, 2
 Schema: _c0, _c1
Expected: _c0 but found: 1
```

In the PR, I propose:
- Checking CSV header only when it exists
- Filter header from the input dataset only if it exists

## How was this patch tested?

Added a test to `CSVSuite` which reproduces the issue.

Closes #22656 from MaxGekk/inferred-header-check.

Authored-by: Maxim Gekk <maxim.gekk@databricks.com>
Signed-off-by: hyukjinkwon <gurwls223@apache.org>
2018-10-09 14:35:00 +08:00
..
catalyst [SPARK-25408] Move to more ideomatic Java8 2018-10-08 09:58:52 -05:00
core [SPARK-25669][SQL] Check CSV header only when it exists 2018-10-09 14:35:00 +08:00
hive [SPARK-25630][TEST] Reduce test time of HadoopFsRelationTest 2018-10-08 13:05:53 -07:00
hive-thriftserver Revert "[SPARK-25408] Move to mode ideomatic Java8" 2018-10-05 11:03:41 +08:00
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-21485][FOLLOWUP][SQL][DOCS] Describes examples and arguments separately, and note/since in SQL built-in function documentation 2017-08-05 10:10:56 -07:00
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.