PostgreSQL Server Programming, 2nd Edition: Extend PostgreSQL using PostgreSQL server programming to create, test, debug, and optimize a range of user-defined functions in your favorite programming language

508 Pages·2015·2.7 MB·English

by  Usama Dar

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PostgreSQL Server Programming Second
Edition
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Table of Contents
PostgreSQL Server Programming Second Edition
Credits
About the Authors
About the Reviewers
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Free access for Packt account holders
Preface
What this book covers
What you need for this book
Who this book is for
Conventions
Reader feedback
Customer support
Downloading the example code
Errata
Piracy
Questions
1. What Is a PostgreSQL Server?
Why program in the server?
Using PL/pgSQL for integrity checks
About this book’s code examples
Switching to the expanded display
Moving beyond simple functions
Data comparisons using operators
Managing related data with triggers
Auditing changes
Data cleaning
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Custom sort orders
Programming best practices
KISS – keep it simple stupid
DRY – don’t repeat yourself
YAGNI – you ain’t gonna need it
SOA – service-oriented architecture
Type extensibility
Caching
Wrapping up – why program in the server?
Performance
Ease of maintenance
Improved productivity
Simple ways to tighten security
Summary
2. Server Programming Environments
Cost of acquisition
Availability of developers
Licensing
Predictability
Community
Procedural languages
Third-party tools
Platform compatibility
Application design
Databases are considered harmful
Encapsulation
What does PostgreSQL offer?
Data locality
More basics
Transactions
General error reporting and error handling
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User-defined functions
Other parameters
More control
Summary
3. Your First PL/pgSQL Function
Why PL/pgSQL?
The structure of a PL/pgSQL function
Accessing function arguments
Conditional expressions
Loops with counters
Statement termination
Looping through query results
PERFORM versus SELECT
Looping Through Arrays
Returning a record
Acting on the function’s results
Summary
4. Returning Structured Data
Sets and arrays
Returning sets
Returning a set of integers
Using a set returning function
Functions based on views
OUT parameters and records
OUT parameters
Returning records
Using RETURNS TABLE
Returning with no predefined structure
Returning SETOF ANY
Variadic argument lists
A summary of the RETURN SETOF variants
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Returning cursors
Iterating over cursors returned from another function
Wrapping up of functions returning cursors
Other ways to work with structured data
Complex data types for the modern world – XML and JSON
XML data type and returning data as XML from functions
Returning data in the JSON format
Summary
5. PL/pgSQL Trigger Functions
Creating the trigger function
Creating the trigger
Working on a simple “Hey, I’m called” trigger
The audit trigger
Disallowing DELETE
Disallowing TRUNCATE
Modifying the NEW record
The timestamping trigger
The immutable fields trigger
Controlling when a trigger is called
Conditional triggers
Triggers on specific field changes
Visibility
Most importantly – use triggers cautiously!
Variables passed to the PL/pgSQL TRIGGER function
Summary
6. PostgreSQL Event Triggers
Use cases for creating event triggers
Creating event triggers
Creating an audit trail
Preventing schema changes
A roadmap of event triggers
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Summary
7. Debugging PL/pgSQL
Manual debugging with RAISE NOTICE
Throwing exceptions
Logging to a file
The advantages of RAISE NOTICE
The disadvantages of RAISE NOTICE
Visual debugging
Installing the debugger
Installing the debugger from the source
Installing pgAdmin3
Using the debugger
The advantages of the debugger
The disadvantages of the debugger
Summary
8. Using Unrestricted Languages
Are untrusted languages inferior to trusted ones?
Can you use untrusted languages for important functions?
Will untrusted languages corrupt the database?
Why untrusted?
Why PL/Python?
Quick introduction to PL/Python
A minimal PL/Python function
Data type conversions
Writing simple functions in PL/Python
A simple function
Functions returning a record
Table functions
Running queries in the database
Running simple queries
Using prepared queries
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Caching prepared queries
Writing trigger functions in PL/Python
Exploring the inputs of a trigger
A log trigger
Constructing queries
Handling exceptions
Atomicity in Python
Debugging PL/Python
Using plpy.notice() to track the function’s progress
Using assert
Redirecting sys.stdout and sys.stderr
Thinking out of the “SQL database server” box
Generating thumbnails when saving images
Sending an e-mail
Listing directory contents
Summary
9. Writing Advanced Functions in C
The simplest C function – return (a + b)
add_func.c
Version 0 call conventions
Makefile
CREATE FUNCTION add(int, int)
add_func.sql.in
Summary for writing a C function
Adding functionality to add(int, int)
Smart handling of NULL arguments
Working with any number of arguments
Basic guidelines for writing C code
Memory allocation
Use palloc() and pfree()
Zero-fill the structures
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Include files
Public symbol names
Error reporting from C functions
“Error” states that are not errors
When are messages sent to the client?
Running queries and calling PostgreSQL functions
A sample C function using SPI
Visibility of data changes
More info on SPI_* functions
Handling records as arguments or returned values
Returning a single tuple of a complex type
Extracting fields from an argument tuple
Constructing a return tuple
Interlude – what is Datum?
Returning a set of records
Fast capturing of database changes
Doing something at commit/rollback
Synchronizing between backends
Writing functions in C++
Additional resources for C
Summary
10. Scaling Your Database with PL/Proxy
Creating a simple single-server chat
Dealing with success – splitting tables over multiple databases
What expansion plans work and when?
Moving to a bigger server
Master-slave replication – moving reads to slave
Multimaster replication
Data partitioning across multiple servers
Splitting the data
PL/Proxy – the partitioning language
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