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  • Book Overview & Buying PostgreSQL Server Programming - Second Edition
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PostgreSQL Server Programming - Second Edition

PostgreSQL Server Programming - Second Edition - Second Edition

By : Dar, Krosing, Jim Mlodgenski
4.5 (8)
Buy this Book
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PostgreSQL Server Programming - Second Edition

PostgreSQL Server Programming - Second Edition

4.5 (8)
By: Dar, Krosing, Jim Mlodgenski
Buy this Book

Overview of this book

This book is for moderate to advanced PostgreSQL database professionals who wish to extend PostgreSQL, utilizing the most updated features of PostgreSQL 9.4. For a better understanding of this book, familiarity with writing SQL, a basic idea of query tuning, and some coding experience in your preferred language is expected.
Table of Contents (16 chapters)
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Preface
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Preface
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What this book covers
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What you need for this book
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Who this book is for
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Conventions
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Reader feedback
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Customer support
Lock Free Chapter
1
1. What Is a PostgreSQL Server?
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1. What Is a PostgreSQL Server?
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Why program in the server?
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About this book's code examples
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Moving beyond simple functions
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Managing related data with triggers
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Auditing changes
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Data cleaning
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Custom sort orders
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Programming best practices
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Caching
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Wrapping up – why program in the server?
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Summary
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2. Server Programming Environments
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2. Server Programming Environments
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Cost of acquisition
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Availability of developers
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Licensing
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Predictability
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Community
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Procedural languages
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Summary
3
3. Your First PL/pgSQL Function
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3. Your First PL/pgSQL Function
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Why PL/pgSQL?
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The structure of a PL/pgSQL function
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Conditional expressions
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Returning a record
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Acting on the function's results
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Summary
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4. Returning Structured Data
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4. Returning Structured Data
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Sets and arrays
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Returning sets
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Using a set returning function
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Functions based on views
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OUT parameters and records
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A summary of the RETURN SETOF variants
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Returning cursors
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Other ways to work with structured data
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Summary
5
5. PL/pgSQL Trigger Functions
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5. PL/pgSQL Trigger Functions
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Creating the trigger function
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Working on a simple "Hey, I'm called" trigger
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The audit trigger
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Disallowing DELETE
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Disallowing TRUNCATE
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Modifying the NEW record
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The immutable fields trigger
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Controlling when a trigger is called
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Visibility
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Variables passed to the PL/pgSQL TRIGGER function
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Summary
6
6. PostgreSQL Event Triggers
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6. PostgreSQL Event Triggers
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Use cases for creating event triggers
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Creating event triggers
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Creating an audit trail
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Preventing schema changes
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A roadmap of event triggers
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Summary
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7. Debugging PL/pgSQL
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7. Debugging PL/pgSQL
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Manual debugging with RAISE NOTICE
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Visual debugging
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Summary
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8. Using Unrestricted Languages
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8. Using Unrestricted Languages
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Are untrusted languages inferior to trusted ones?
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Can you use untrusted languages for important functions?
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Will untrusted languages corrupt the database?
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Why untrusted?
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Quick introduction to PL/Python
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Thinking out of the "SQL database server" box
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Summary
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9. Writing Advanced Functions in C
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9. Writing Advanced Functions in C
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The simplest C function – return (a + b)
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Adding functionality to add(int, int)
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Basic guidelines for writing C code
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Error reporting from C functions
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Running queries and calling PostgreSQL functions
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Handling records as arguments or returned values
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Fast capturing of database changes
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Doing something at commit/rollback
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Synchronizing between backends
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Writing functions in C++
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Additional resources for C
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Summary
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10. Scaling Your Database with PL/Proxy
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10. Scaling Your Database with PL/Proxy
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Creating a simple single-server chat
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Dealing with success – splitting tables over multiple databases
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Connection Pooling
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Summary
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11. PL/Perl – Perl Procedural Language
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11. PL/Perl – Perl Procedural Language
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When to use PL/Perl
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Installing PL/Perl
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A simple PL/Perl function
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Passing and returning non-scalar types
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Writing PL/Perl triggers
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Untrusted Perl
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Summary
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12. PL/Tcl – Tcl Procedural Language
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12. PL/Tcl – Tcl Procedural Language
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Installing PL/Tcl
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A simple PL/Tcl function
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Passing and returning arrays
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Passing composite-type arguments
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Accessing databases
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Writing PL/Tcl triggers
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Untrusted Tcl
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Summary
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13. Publishing Your Code as PostgreSQL Extensions
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13. Publishing Your Code as PostgreSQL Extensions
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When to create an extension
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Unpackaged extensions
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Extension versions
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The .control file
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Building an extension
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Installing an extension
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Viewing extensions
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Publishing your extension
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Installing an extension from PGXN
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Summary
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14. PostgreSQL as an Extensible RDBMS
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14. PostgreSQL as an Extensible RDBMS
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What can't be extended?
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Creating a new operator
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Creating index access methods
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Creating user-defined aggregates
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Using foreign data wrappers
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Summary
15
Index
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Index

Basic guidelines for writing C code

After having written our first function, let's look at some of the basic coding guidelines for PostgreSQL backend coding.

Memory allocation

One of the places you have to be extra careful when writing C code in general is memory management. For any non-trivial C program, you have to carefully design and implement your programs, so that all your allocated memory is freed when you are done with it, or else you will "leak memory" and will probably run out of memory at some point.

As this is also a common concern for PostgreSQL, it has its own solution—memory contexts. Let's take a deeper dive into them.

Use palloc() and pfree()

Most PostgreSQL memory allocations are done using PostgreSQL's memory allocation function palloc() and not standard C malloc(). What makes palloc() special is that it allocates the memory in the current context and the whole memory is freed in one go when the context is destroyed. For example, the transaction context—which is the current...

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