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PostgreSQL Server Programming

PostgreSQL Server Programming

4.7 (9)
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PostgreSQL Server Programming

PostgreSQL Server Programming

4.7 (9)

Overview of this book

Learn how to work with PostgreSQL as if you spent the last decade working on it. PostgreSQL is capable of providing you with all of the options that you have in your favourite development language and then extending that right on to the database server. With this knowledge in hand, you will be able to respond to the current demand for advanced PostgreSQL skills in a lucrative and booming market."PostgreSQL Server Programming" will show you that PostgreSQL is so much more than a database server. In fact, it could even be seen as an application development framework, with the added bonuses of transaction support, massive data storage, journaling, recovery and a host of other features that the PostgreSQL engine provides. This book will take you from learning the basic parts of a PostgreSQL function, then writing them in languages other than the built-in PL/PgSQL. You will see how to create libraries of useful code, group them into even more useful components, and distribute them to the community. You will see how to extract data from a multitude of foreign data sources, and then extend PostgreSQL to do it natively. And you can do all of this in a nifty debugging interface that will allow you to do it efficiently and with reliability.
Table of Contents (17 chapters)
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PostgreSQL Server Programming
Credits
About the Authors
About the Reviewer
www.PacktPub.com
Preface
Index

Returning cursors


Another method of getting a tabular data out of function is by using a CURSOR.

CURSOR, or a portal as it is sometimes referenced in PostgreSQL documentation, is an internal structure which contains a prepared query plan ready to return rows from the query. Sometimes the cursor needs to retrieve all the data for the query at once, but for many queries it does lazy fetching. For example, queries that need to scan all of the data in a table such as SELECT * FROM xtable, only read as much data as needed for each FETCH from the cursor.

In plain SQL, CURSOR is defined as follows:

DECLARE mycursor CURSOR  FOR <query >;

And later the rows are fetched using the following statement:

FETCH NEXT FROM  mycursor;

While you can use a cursor to handle the data from a set returning function the usual way, by simply declaring the cursor as DECLARE mycursor CURSOR FOR SELECT * FROM mysetfunc();, it is many times more beneficial to have the function itself just return a cursor.

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