Libpq++ Download
The C connector for PostgreSQLlibpqxx is the official C client API for, the enterprise-strength open-source relational database. (If 'PostgreSQL' is too verbose, call it by its shorter name, postgres).If you are writing software in C that needs to access databases managed by postgres—on just about any platform—then libpqxx is the library you use.
It is the standard C language binding for the postgres RDBMS.The source code for libpqxx is available under the BSD license, so you're free to, pass it on to others, change it, sell it, include it in your own code, and share your changes with anyone you choose. No charge, no catch. Also, no guarantees.:-)News 2019-07-29: Major changes for 7.0Well, we always knew that libpqxx 7.0 would be a major change. Here's a quick rundown of how design has evolved so far.Connection state is now really, really simple. A connection is just what you'd expect it to be — a dumb, direct, simple connection to the database. If it breaks, it remains broken. If you still need a connection after that, you'll just have to make a new one.
Libpq++ Download
No sleeping connections, lazy connections, or asynchronous connections. (I reviewed the control flow and decided that those last ones really didn't buy us much, but boy did they complicate the code!) I guess we'll want some async cleverness in the future, but I suppose it can wait until compiler support is better.Table streams have been replaced with streamfrom and streamto, as expected.The big one that's keeping me occupied right now though is string conversion: converting values in your code to and from strings which you can exchange with the database. The old code is all based on std::string, but of course I'd like to save you the allocation overhead if I can.Which means using std::stringview wherever we can. For fromstring that's easy: it now takes a std::stringview instead of a std::string.
Easy money.The hard part is the converse conversion: from a value to a string. Unfortunately we do have to deal with libpq, which uses C-style strings almost exclusively.
What we end up with is a mishmash of std::string, std::stringview, and const char. depending on the situation. I'm working out a low-overhead compromise based on a new class called str. This templated class holds one value, and can give you its std::stringview and/or const char.
representations as desired. It's an immutable string, so implementations pick internal representations on a case-by-case basis. Layered on top of str you still get tostring, and underneath there's a function template similar to std::tochars.But we're not there yet. I'm still struggling to work out all the templating machinery, the occasional inverted dependencies (sometimes it's more efficient to invert the layering!), and the joys of SFINAE. And getting it working is only half the job: I'll also have to make it simple. And once I've done that, I'll need to document the new ways of defining your own conversions.
Libpq++ Windows
It could be a lot more complicated in some cases, if you really care about performance. But of course I'd like you to have the easy option when you want it.Finding Everything WhereWhatDocumentation hosted on Read The DocsGet source, report bugs, submit patches, request changesWho made all this?Technical OverviewThis library works on top of the C-level API library, libpq. It comes with postgres. You will link your program with both libpqxx and libpq, in that order.Coding with libpqxx revolves around transactions. Transactions are a central concept in database management systems, but they are widely under-appreciated among application developers. In libpqxx, they're fundamental.With conventional database APIs, you issue commands and queries to a database session or connection, and optionally create the occasional transaction. In libpqxx you start with a connection, but you do all your SQL work in transactions that you open in your connection.
You commit each transaction when it's complete; if you don't, all changes made inside the transaction get rolled back.There are several types of transactions with various 'quality of service' properties. If you really don't want a transaction, one of the available transaction types is called nontransaction.
This transaction type provides basic non-transactional behaviour. (This is sometimes called 'autocommit': it commits every command right away).Every command or query returns a result. Your query fetches its result data immediately when you execute it, and stores it in the result. Don't check your result for errors; failures show up as regular C exceptions.Keep result objects around for as long as you need them, completely separate from the connections and transactions that originated them.
You can access the rows in a result using standard iterators, or more like an array using numerical indexes. Inside each row you can access the fields by standard iterators, numerical indexes, or using column names.Brief exampleCan't have a database example without an Employee table. Here's a simple program: find an employee by name, and raise their salary by 1 whatever-it-is-they-get-paid-in.This example is so simple that anything that goes wrong crashes the program. You won't need to do a lot more to fix that, but we'll get to it later.
Hi there.I am having trouble getting C to interface with a PostgreSQL database. Iwant to use the libpq library, but can't quite figure out quite how.I am using PostgreSQL 7.3.1 on WinXP. This distribution doesn't seem to haveshipped with libpq, so I downloaded it seperately. The problem is that Ican't seem to get any of the example code to compile. I am using MinGW.
Ihave linked my project to the libpq.a library, included all the source filesin the libpq4.0 folder that I downloaded, and specified the path to theirheaders.Does anyone have any experience with libpq on windows using MinGW?Any help would be much appreciated.Thanks,Josh Harris.