Apache phoenix: Past, Present and Future of SQL over HBAse

© Hortonworks Inc. 2011 – 2014. All Rights Reserved
Apache Phoenix and HBase: Past, Present
and Future of SQL over HBase
Enis Soztutar (enis@hortonworks.com)

About Me
Enis Soztutar
Committer and PMC member in Apache HBase, Phoenix, and Hadoop
HBase/Phoenix team @Hortonworks
Twitter @enissoz
Disclaimer: Not a SQL expert!

Outline
PART I – The Past (a.k.a. All the existing stuff)
 Phoenix the basics
 Architecture
 Overview of existing Phoenix features
PART II – The Present (a.k.a. All the recent stuff)
 Look at recent releases
 Transactions
 Phoenix Query Server
 Other features
PART III – The Future (a.k.a. All the upcoming stuff)
 Calcite integration
 Phoenix – Hive

Part I – The Past
All the existing stuff !

Obligatory Slide - Who uses Phoenix

Phoenix – The Basics
• Hope everybody is familiar with HBase
• Otherwise you are in the wrong talk!
• What is wrong with pure-HBase?
• HBase is a powerful, flexible and extensible “engine”
• Too low level
• Have to write java code to do anything!
• Phoenix is relational layer over HBase
• Also described as a SQL-Skin
• Looking more and more like a generic SQL engine
• Why not Hive / Spark SQL / other SQL-over-Hadoop
• OTLP versus OLAP
• As fast as HBase, 1 ms query, 10K-1M qps

Why SQL?

From CDK Global
slides
https://phoenix.apache.
org/presentations/Strata
HadoopWorld.pdf

HBase Architecture
DataNode
RegionServer 2
T:foo, region:a
T:bar, region:54
T:foo, region:t
Application
HBase client
DataNode
RegionServer 1
T:foo, region:c
T:bar, region:14
T:foo, region:d
DataNode
RegionServer 3
T:bar, region:32
T:foo, region:k
ZooKeeper
Quorum

Phoenix Architecture
DataNode
RegionServer 2
T:foo, region:c
T:bar, region:54
T:foo, region:t
Phoenix RPC
endpoint
px
px
Application
Phoenix client / JDBC
HBase client
DataNode
RegionServer 1
T:foo, region:c
T:bar, region:14
T:foo, region:d
Phoenix RPC
endpoint
px
px
DataNode
RegionServer 3
T:SYSTEM.CATALOG
T:bar, region:32
T:foo, region:k
Phoenix RPC
endpoint
px
px
ZooKeeper
Quorum

Phoenix Goodies
SQL DataTypes
Schemas / DDL / HBase table properties
Composite Types (Composite Primary Key)
Map existing HBase tables
Write from HBase, read from Phoenix
Salting
Parallel Scan
Skip scan
Filter push down
Statistics Collection / Guideposts

DDL Example
CREATE TABLE IF NOT EXISTS METRIC_RECORD (
METRIC_NAME VARCHAR,
HOSTNAME VARCHAR,
SERVER_TIME UNSIGNED_LONG NOT NULL
METRIC_VALUE DOUBLE,
…
CONSTRAINT pk PRIMARY KEY (METRIC_NAME, HOSTNAME,
SERVER_TIME))
DATA_BLOCK_ENCODING=’FAST_DIFF', TTL=604800,
COMPRESSION=‘SNAPPY’
SPLIT ON ('a', 'k', 'm');

METRIC_NAME HOSTNAME SERVER_TIME METRIC_VALUE
Regionserver.readRequestCount cn011.hortonworks.com 1396743589 92045759
Regionserver.readRequestCount cn011.hortonworks.com 1396767589 93051916
Regionserver.readRequestCount cn011.hortonworks.com …. …
Regionserver.readRequestCount cn012. hortonworks.com 1396743589
….. … … …
Regionserver.wal.bytesWritten cn011.hortonworks.com
Regionserver.wal.bytesWritten …. …. …
SORT ORDERSORTORDER
HBASE ROW KEY OTHER COLUMNS

Parallel Scan
SELECT * FROM METRIC_RECORD;
CLIENT 4-CHUNK PARALLEL 1-WAY
FULL SCAN OVER METRIC_RECORD
Region1
Region2
Region3
Region4
Client
RS3RS2
RS1
scanscanscanscan

Filter push down
SELECT * FROM METRIC_RECORD
WHERE SERVER_TIME > NOW() - 7;
CLIENT 4-CHUNK PARALLEL 1-WAY
FULL SCAN OVER METRIC_RECORD
SERVER FILTER BY
SERVER_TIME > DATE
'2016-04-06 09:09:05.978’
Region1
Region2
Region3
Region4
Client
RS3RS2RS1
scanscanscanscan
Server-side Filter

Skip Scan
WHERE METRIC_NAME LIKE 'abc%'
AND HOSTNAME in ('host1’,
'host2');
CLIENT 1-CHUNK PARALLEL 1-WAY SKIP
SCAN ON 2 RANGES OVER
METRIC_RECORD ['abc','host1'] -
['abd','host2']
Region1
Region2
Region3
Region4
Client
RS3RS2RS1
Skip scan

TopN
WHERE SERVER_TIME > NOW() - 7
ORDER BY HOSTNAME LIMIT 5;
CLIENT 4-CHUNK PARALLEL 4-WAY FULL
SCAN OVER METRIC_RECORD
SERVER FILTER BY SERVER_TIME > …
SERVER TOP 5 ROWS SORTED BY
[HOSTNAME]
CLIENT MERGE SORT
Region1
Region2
Region3
Region4
Client
RS3RS2RS1
scanscanscanscan
Sort by HOSTNAME
Return only 5
ROWS

Aggregation
SELECT METRIC_NAME, HOSTNAME,
AVG(METRIC_VALUE)
FROM METRIC_RECORD
WHERE SERVER_TIME > NOW() - 7
GROUP BY METRIC_NAME, HOSTNAME
ORDER BY METRIC_NAME, HOSTNAME;
CLIENT 4-CHUNK PARALLEL 1-WAY FULL
SCAN OVER METRIC_RECORD
SERVER FILTER BY SERVER_TIME > …
SERVER AGGREGATE INTO ORDERED
DISTINCT ROWS BY
[METRIC_NAME, HOSTNAME]
CLIENT MERGE SORT
Region1
Region2
Region3
Region4
Client
RS3RS2RS1
scanscanscanscan
Return only
aggregated data by
METRIC_NAME,
HOSTNAME

Joins and subqueries in Phoenix
Grammar
• Inner, Left, Right, Full outer join, Cross join
• Semi-join / Anti-join
Algorithms
• Hash-join, sort-merge join
• Hash-join table is computed and pushed to each regionserver from client
Optimizations
• Predicate push-down
• PK-to-FK join optimization
• Global index with missing columns
• Correlated query rewrite

Joins and subqueries in Phoenix
Phoenix can execute most of TPC-H queries!
No nested loop join
With Calcite support, more improvements soon
No statistical Guided join selection yet
Not very good at executing very big joins
• No generic YARN / Tez execution layer
• But Hive / Spark support for generic DAG execution

Secondary Indexes
HBase table is a sorted map
• Everything in HBase is sorted in primary key order
• Full or partial scans in sort order is very efficient in HBase
• Sort data differently with secondary index dimensions
Two types
• Global index
• Local index
Query
• Indexes are “covered”
• Indexes are automatically selected from queries
• Only covered columns are returned from index without going back to data table

Global and Local Index
Global Index
• A single instance for all table data in a
different sort order
• A different HBase table per index
• Optimized for read-heavy use cases
• Can be one edit “behind” actual primary
data
• Transactional tables indices have ACID
guarantees
• Different consistency / durability for
mutable / immutable tables
Local Index
• Multiple mini-instances per region
• Uses same HBase table, different cf
• Optimized for write-heavy use cases
• Atomic commit and visibility (coming soon)
• Queries have to ask all regions for relevant
data from index

Part II – The Present
All the recent stuff !

Release Note Highlights
4.4
• Functional Indexes
• UDFs
• Query Server
• UNION ALL
• MR Index Build
• Spark Integration
• Date built-in functions
4.5
• Client-side per-statement metrics
• SELECT without FROM
• ALTER TABLE with VIEWS
• Math and Array built-in functions

Release Note Highlights
4.6
• ROW_TIMESTAMP for HBase native timestamps
• Support for correlate variable
• Support for un-nesting arrays
• Web-app for visualizing trace info (alpha)
4.7
• Transaction support
• Enhanced secondary index consistency guarantees
• Statistics improvements
• Perf improvements

Row Timestamps
A pseudo-column for HBase native timestamps (versions)
Enables setting and querying cell timestamps
Perfect for time-series use cases
• Combine with FIFO / Date Tiered Compaction policies
• And HBase scan file pruning based on min-max ts for very efficient scans
CREATE TABLE METRICS_TABLE (
CREATED_DATE NOT NULL DATE,
METRIC_ID NOT NULL CHAR(15), METRIC_VALUE LONG
CONSTRAINT PK PRIMARY KEY(CREATED_DATE ROW_TIMESTAMP,
METRIC_ID)) SALT_BUCKETS = 8;

Transactions
Uses Tephra
Snapshot isolation semantics
Completely optional.
• Can be enabled per-table (TRANSACTIONAL=true)
• Transactional and non-transactional tables can live side by side
Transactions see their own uncommitted data
Released in 4.7, will GA in 5.0
Optimistic Concurrency Control
• No locking for rows
• Transactions have to roll back and undo their writes in case of conflict
• Cost of conflict is higher

Tephra Architecture
RegionServer 2
Tephra / HBase Client
RegionServer 1 RegionServer 3
HBase client
ZooKeeper
Quorum
Tephra Trx Manager
(active)
Tephra Trx Manager
(standby)

Transaction Lifecycle
From Tephra
presentation
http://www.slideshare.n
et/alexbaranau/transacti
ons-over-hbase

Phoenix Query Server
Similar to HBase REST Server / Hive Server 2
Built on top of Calcite’s Avatica Server with Phoenix bindings
Embeds a Phoenix thick client inside
No client side sorting / join!
Protobuf-3.0 over HTTP protocol
Has a (thin) JDBC driver
Allows ODBC driver for Phoenix

Phoenix architecture revisited (thick client)
RegionServer 2
T:foo, region:d
Phoenix RPC
endpoint
px
Application
RegionServer 1
T:foo, region:d
Phoenix RPC
endpoint
px
RegionServer 3
T:foo, region:d
Phoenix RPC
endpoint
px
HBase client

Phoenix Query Server (thin client)
RegionServer 2
T:foo, region:d
Phoenix RPC
endpoint
px
Application
Phoenix thin client / JDBC
RegionServer 1
T:foo, region:d
Phoenix RPC
endpoint
px
RegionServer 3
T:foo, region:d
Phoenix RPC
endpoint
px
HBase client
HBase client
HBase client

Other new features (4.8+)
Shaded client by default. No more library dependency problems!
Phoenix schema mapping to HBase namespace
• Allows using isolation and security features of HBase namespaces
• Standard SQL syntax:
CREATE SCHEMA FOO;
USE FOO;
LIMIT / OFFSET
• We already had LIMIT. Now we have OFFSET
• Together with Row-Value-Constructs, covers most of cursor use cases

Part III – The Future
All the upcoming stuff !

Local Index
• Local Index re-implemented
• Instead of a different table, now local index data is kept within the same data
table
• Local index data goes into a different column family
• Index and data is committed together atomically without external transactions
• Bunch of stability improvements with region splits and merges

Calcite Integration
Calcite is a framework for:
• Query parser
• Compiler
• Planner
• Cost based optimizer
SQL-92 compliant
Based on relational algebra
Cost based optimizer with default rules + pluggable rules per-backend
Used by Hive / Drill / Kylin / Samza, etc.

Calcite Integration

Phoenix - Hive integration
Hive is a very rich and generic execution engine
Uses Tez + YARN to execute arbitrary DAG
Hive integration enables big joins and other Hive features
Phoenix DDL with HiveQL
Data insert / update delete (DML) with HiveQL
Predicate pushdown, salting, partitioning, partition pruning, etc
Can use secondary indexes as well since it uses Phoenix compiler
https://issues.apache.org/jira/browse/PHOENIX-2743

Future<Phoenix>
JSON support
TPC-H / Microstrategy / Tableau queries
Sqoop integration
Support Omid based transactions
Dogfooding within the Hadoop-ecosystem
• Ambari Metrics Service (AMS) uses Phoenix
• YARN will soon use HBase / Phoenix (ATS)
STRUCT type
Improvements to cost based optimization
Security and other HBase features used from Phoenix
See https://phoenix.apache.org/roadmap.html

Further Reference
Even more info on https://phoenix.apache.org
 New Features: https://phoenix.apache.org/recent.html
 Roadmap: https://phoenix.apache.org/roadmap.html
Get involved in mailing lists
 user@phoenix.apache.org
 dev@phoenix.apache.org

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Apache phoenix: Past, Present and Future of SQL over HBAse

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