4f274a4de9
### What changes were proposed in this pull request? Spark introduced CHAR type for hive compatibility but it only works for hive tables. CHAR type is never documented and is treated as STRING type for non-Hive tables. However, this leads to confusing behaviors **Apache Spark 3.0.0-preview2** ``` spark-sql> CREATE TABLE t(a CHAR(3)); spark-sql> INSERT INTO TABLE t SELECT 'a '; spark-sql> SELECT a, length(a) FROM t; a 2 ``` **Apache Spark 2.4.5** ``` spark-sql> CREATE TABLE t(a CHAR(3)); spark-sql> INSERT INTO TABLE t SELECT 'a '; spark-sql> SELECT a, length(a) FROM t; a 3 ``` According to the SQL standard, `CHAR(3)` should guarantee all the values are of length 3. Since `CHAR(3)` is treated as STRING so Spark doesn't guarantee it. This PR forbids CHAR type in non-Hive tables as it's not supported correctly. ### Why are the changes needed? avoid confusing/wrong behavior ### Does this PR introduce any user-facing change? yes, now users can't create/alter non-Hive tables with CHAR type. ### How was this patch tested? new tests Closes #27902 from cloud-fan/char. Authored-by: Wenchen Fan <wenchen@databricks.com> Signed-off-by: Dongjoon Hyun <dongjoon@apache.org> |
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| .. | ||
| catalyst | ||
| core | ||
| hive | ||
| hive-thriftserver | ||
| create-docs.sh | ||
| gen-sql-api-docs.py | ||
| gen-sql-config-docs.py | ||
| mkdocs.yml | ||
| 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.