The document discusses Cloudera's Impala, a real-time SQL query engine designed for Hadoop that provides high-performance, low-latency access to data stored in HDFS and HBase. Impala supports various SQL query operations and is optimized for both analytical and transactional workloads, achieving significant speed improvements over traditional MapReduce, particularly for queries involving large datasets. The architecture includes a distributed processing model with high disk throughput, although it has some current limitations such as the absence of User Defined Functions and certain optimizations.

1. Cloudera Impala
Real Time Query for HDFS and HBase
Alexander Alten-Lorenz, Cloudera INC
Tuesday, July 2, 13

2. 2
Beyond Batch
What is Impala
Capability
Architecture
Demo
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3. Beyond Batch
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For some things MapReduce is just too slow
Apache Hive:
MapReduce execution engine
High-latency, low throughput
High runtime overhead
Google realized this early on
Analysts wanted fast, interactive results
Tuesday, July 2, 13

4. Dremel
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Google paper (2010)
“scalable, interactive ad-hoc query system for
analysis of read-only nested data”
Columnar storage format
Distributed scalable aggregation
“capable of running aggregation queries over
trillion-row tables in seconds”
http://research.google.com/pubs/pub36632.html
Tuesday, July 2, 13

5. Impala: Goals
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General-purpose SQL query engine for Hadoop
For analytical and transactional workloads
Support queries that take μs to hours
Run directly with Hadoop
Collocated daemons
Same file formats
Same storage managers (NN, metastore)
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6. Impala: Goals
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High performance
C++
runtime code generation (LLVM)
direct access to data (no MapReduce)
Retain user experience
easy for Hive users to migrate
100% open-source
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7. Impala: Capability
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HiveQL (subset of SQL92)
select, project, join, union, subqueries,
aggregation, insert, order by (with limit)
DDL
Directly queries data in HDFS & HBase
Text files (compressed)
Sequence files (snappy/gzip)
Avro &Trevni
GA features
Tuesday, July 2, 13

8. Impala: Capability
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Familiar and unified platform
Uses Hive’s metastore
Submit queries via ODBC | BeeswaxThrift API
Query is distributed to nodes with relevant data
Process-to-process data exchange
Kerberos authentication
No fault tolerance
Tuesday, July 2, 13

9. Impala: Performance
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Greater disk throughput
~100MB/sec/disk
I/O-bound workloads faster by 3-4x
Queries that require multiple map-reduce phases
in Hive are significantly faster in Impala (up to 45x)
Queries that run against in-memory cached data
see a significant speedup (up to 90x)
Tuesday, July 2, 13

10. Impala:Architecture
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impalad
runs on every node
handles client requests (ODBC, thrift)
handles query planning & execution
statestored
provides name service
metadata distribution
used for finding data
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11. Impala:Architecture
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12. Impala:Architecture
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13. Impala:Architecture
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14. Impala:Architecture
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15. Current limitations
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1.0.1 (available since May 2013)
No SerDes
No User Defined Functions (UDF’s)
impalad’s only read statestored metadata at
startup
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16. Futures
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DDL support (CREATE)
Rudimentary cost-based optimizer (CBO)
metadata distribution through statestored
Doug Cutting’sTrevni
Columnar storage format like Dremel’s
Impala +Trevni = Dremel superset
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17. Demo
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impala-user@cloudera.com
alexander@cloudera.com
@mapredit
mapredit.blogspot.com
Web: http://goo.gl/7sxdp
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18. Tuesday, July 2, 13