Rapid debugging and profiling for database issues

Grab
some
coffee
and
enjoy
the pre-
show
banter
before

HOST:
Eric Kavanagh
@eric_kavanagh

THELINEUP
ANALYST:
Dez Blanchfield
Data Scientist,
The Bloor Group
ANALYST:
Robin Bloor
Chief Analyst,
The Bloor Group
GUEST:
Bert Scalzo
Senior Product Manager,
IDERA

About Bug Hunting
Robin Bloor Ph.D.

Famous Bugs
u 1998: NASA’s Mars Climate Orbiter lost in
space: (units problem)
u Ariane 5 Flight 501 self-destructs after
multiple computer failures (1996)
u Soviet Gas Pipeline in 1982 – stolen
automated control software (CIA hacked)
u Morris Worm – a harmless coding
experiment became a worm (Cornell Univ
- 1988)
u Pentium chip math error (1993)
u Apple Maps (2012) – disastrous launch
u AT&T long distance outage (1990) costs
$60m
u UK insurance company (1993) database
wipes data

file://localhost/Users/robinbloor2/Dropbox/~Deskto
p/bottlenecks.jpg
The Impedance Mismatch
The RDBMS stores data
organized in tables
The OO coder manipulates data
organized in object structures,
with associated methods
The data does not simply map to
the database table structures so
a mapping is necessary
Basically: hierarchies, types,
result sets, poor APIs, language
bindings, tools

p/bottlenecks.jpg
The Impedance Mismatch
SQL has:
DDL (for data definition)
DML (for Select, Project and
Join)
But it has little MML (Math) or
TML (Time)
Usually result sets are brought to
the client for further analytical
manipulation, but this creates
problems
Alternatively doing all analytical
manipulation in the database
creates problems

p/bottlenecks.jpg
Database Performance Bottlenecks
CPU: CPU overload, context
switches, I/O waits, CPU cache,
Backplane throughput
Memory: Thrashing,
fragmentation
Disk: Caching, I/O saturation,
fragmentation, SSD performance
Network Overhead (SANs, NAS,
local disk)
Locking

Database Performance Factors
Bad database design
Bad program design
Concurrency, workload
mixing
Load balancing
Capacity planning – data
growth
Data layer issues

In A Few Words
Database debugging can be onerous
and non-trivial

There are many stories about how the terms “bug” and
“debugging” came about – one of them claims that “On
September 9, 1945, in the USA, a Harvard technical
team looked at Panel F of the Harvard's Mark II
computer, and found something unusual between points
in Relay 70”.

Apparently it was a moth, which they promptly
removed and taped in the log book. Supposedly the
legendary Grace Hopper added a caption which read
“First actual case of bug being found," and it’s long
been claimed that this was the first time anyone used
the word bug to describe a computer glitch. Naturally,
the term debugging followed.

A Boy named Robert'); DROP TABLE students;--
Little Bobble Tables..

I doubt any programmer anticipated a “hit & run” of their code
by a motor vehicle, but never under estimate angry geeks..
Not a bug bug funny all the same

there was a time when
debugging and profiling code
could be done by mere mortals..
that time has long passed..

Some Code Reviews Require Rocket Science

x$objQuery = $this->db->query
( "SELECT rd.*, ((rd.rd_numberofrooms) - (select
sum(rn.reservation_numberofrooms) as
count_reserve_room from reservation as rn WHERE
rn.reservation_rd_id = rd.rd_id AND
(str_to_date('$data_Check_in_date','%d-%m-%y')
BETWEEN
str_to_date(rn.reservation_check_in_date,'%d-%m-
%y') AND
str_to_date(rn.reservation_check_out_date,'%d-%m-
%y') OR str_to_date('$data_Check_out_date','%d-%m-
%y') BETWEEN
%y') AND
%y') OR str_to_date('$data_Check_in_date','%d-%m-
%y') <=
%y') AND str_to_date('$data_Check_out_date','%d-%m-
%y') ) )) as reserve
FROM room_details rd LEFT JOIN reservation rn ON
rd.rd_id = rn.reservation_rd_id WHERE NOT EXISTS
(
SELECT rn.* FROM reservation rn WHERE
rn.reservation_rd_id = rd.rd_id
AND (str_to_date('$data_Check_in_date','%d-%m-%y')
BETWEEN
%y') AND
%y') BETWEEN
%y') AND
%y') <=
%y') >=
%y'))
AND (rd.rd_numberofrooms <= (select
sum(rn.reservation_numberofrooms) as
count_reserve_room from reservation as rn WHERE
rn.reservation_rd_id = rd.rd_id AND
(str_to_date('$data_Check_in_date','%d-%m-%y')
BETWEEN
%y') AND
%y') BETWEEN
%y') AND
%y') <=
%y') ) ) )
)
");
www.quora.com/Whats-the-most-complex-SQL-query-you-ever-wrote

© 2017 IDERA, Inc. All rights reserved.
RAPID RESPONSE:
DATABASE DEBUGGING AND
PROFILING TO THE RESCUE
Bert Scalzo, Senior Product Manager

25© 2017 IDERA, Inc. All rights reserved.
PROGRAMMING HISTORY
•1951 – Assembly
•1952 – Autocode
•1954 – IPL
•1955 – FLOW-MATIC
•1957 – FORTRAN
•1957 – COMTRAN
•1958 – LISP
•1958 – ALGOL 58
•1959 – FACT
•1959 – COBOL
•1959 – RPG
•1962 – APL
•1962 – Simula
•1962 – SNOBOL
•1963 – CPL
•1964 – Speakeasy
•1964 – BASIC
•1964 – PL/I
•1966 – JOSS
•1967 – BCPL
•1968 – Logo
•1969 – B
•1970 – Pascal
•1970 – Forth
•1972 – C
•1972 – Smalltalk
•1972 – Prolog
•1973 – ML
•1975 – Scheme
•1978 – SQL
•1980 – C++
•1983 – Ada
•1984 – Common Lisp
•1984 – MATLAB
•1985 – Eiffel
•1986 – Objective-C
•1986 – Erlang
•1987 – Perl
•1988 – Tcl
•1988 – Wolfram Language
•1989 – FL
•2000 – ActionScript
•2001 – C#
•2003 – Groovy
•2003 – Scala
•2005 – F#
•2006 – PowerShell
•2007 – Clojure
•2009 – Go
•2010 – Rust
•2011 – Dart
•2012 – Julia
•2014 – Swift
Note this point in history. Can you
guess why it’s marked? (session title)

§ Instrumentation / Print Statements / Trace File
§ Interactive Debugger
• First appeared in 1977
• Good for finding logic mistakes (i.e. effectiveness)
• Remote Debugging (special case – e.g. database)
• Common Terminology
• Breakpoints
• Watch values
• Step into
• Step over
DEBUGGING

PROFILING
§ Sampling / Instruction Set Simulators
§ Instrumentation / Print Statements / Trace File
§ Profiler (Dynamic Program Analysis)
• First appeared in 1979
• Good for finding resource consumption and performance
bottlenecks (i.e. efficiency)
• Generally separate & distinct from the debugger
• Not generally utilized as often as debuggers

DB LANGUAGES
§ Some database vendors offer 3GL languages that
“compile code” within the database
• Oracle: PL/SQL
• SQL Server: Transact-SQL (T-SQL)
• SQL-1999: SQL/PSM
• PostgreSQL: PL/pgSQL
• DB2: SQL PL
• Informix: SPL

DB OBJECTS
§ What database objects are built using procedural
languages?
• Triggers
• (Stored) Procedures
• (Stored) Functions
• Packages (Oracle only)

DEBUGGER EXAMPLE (OLD WAY)

DEBUGGER EXAMPLE (INTERACTIVE)
Hover over variable to see
value
Stepping cursor a line at a time
Setting a breakpoint to run to
Local variables autowatched
Call stack for all procedural
code

PROFILER EXAMPLE #1 (DEBUGGER)
This loop consumed most time,
so anything I can do inside it to
improve performanceshould
pay dividends

PROFILER EXAMPLE #2 (CODE ANALYST)
This loop consumed most time,
so anything I can do inside it to
improve performanceshould
pay dividends

BUSINESS REQUIREMENTS
§ Since we write code to perform some task, we must mandatorily
perform the task correctly (i.e. effective)
• DEBUGGER
§ Since users are impatient and want the results even before they
press the key, or preferably yesterday (i.e. efficient)
• PROFILER
§ Without these tools, we’re shooting blindfolded!

DEMO
Will demonstrate typical database debugger and profiler in
a typical database administration and/or development tool
like IDERA’s DBArtisan®
and Rapid SQL®

Q&A

The Archive Trifecta:
• Inside Analysis www.insideanalysis.com
• SlideShare www.slideshare.net/InsideAnalysis
• YouTube www.youtube.com/user/BloorGroup
THANK YOU!

Rapid debugging and profiling for database issues

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