2f422398b5
## What changes were proposed in this pull request? We have optimization on global limit to evenly distribute limit rows across all partitions. This optimization doesn't work for ordered results. For a query ending with sort + limit, in most cases it is performed by `TakeOrderedAndProjectExec`. But if limit number is bigger than `SQLConf.TOP_K_SORT_FALLBACK_THRESHOLD`, global limit will be used. At this moment, we need to do ordered global limit. ## How was this patch tested? Unit tests. Closes #22344 from viirya/SPARK-25352. Authored-by: Liang-Chi Hsieh <viirya@gmail.com> Signed-off-by: Wenchen Fan <wenchen@databricks.com> |
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catalyst | ||
core | ||
hive | ||
hive-thriftserver | ||
create-docs.sh | ||
gen-sql-markdown.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 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
.