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Integrating Perl and Databases

Integrating Perl and Databases. Making simple things easy and difficult things possible Tim Bunce. August 1997. Why?. Why Perl?. Fewer lines of code faster development / fewer errors / easier maintenance “A picture is worth a thousand words” vs “Can’t see the wood for the trees”

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Integrating Perl and Databases

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  1. IntegratingPerl and Databases Making simple things easyand difficult things possible Tim Bunce August 1997

  2. Why?

  3. Why Perl? • Fewer lines of code • faster development / fewer errors / easier maintenance • “A picture is worth a thousand words” vs “Can’t see the wood for the trees” • Freedom of expression - “There’s more than one way to do it” • The tool builders tool factory

  4. Why Perl for Databases? • Ideally suited to data processing: • parsing, cleansing / filtering / merging and formatting • Applications • Data Migration • Data acquisition and reporting • Web Page creation • Building sharper tools faster

  5. Your Mission... should you choose to accept it...

  6. The Task • Read a tabular text report file of product codes and costs CODE DESCRIPTION COST OTHER NOTES ---- ----------- ------ ------------------- 1201 WIDGET 37A 500.00 LEFT HANDED ONLY 1202 BRACKET X7J 790.00 REDUCED FROM 800.00 1203 FLANGE 9Q7 449.00 LIMITED STOCK • Read a CSV file of product codes, price markup and comments 1201,0.90,Special Offer for limited period only 1202,1.30, • Output a new tabular report containing the new product prices and comments word wrapped in a narrow field

  7. Reading the CSV file open MARGIN, “<margin.csv” or die “open margin.csv: $!”; while (<MARGIN>) { chop; ($prod, $margin, $notes) = split /,/; $prod_margin{$prod} = $margin; $prod_notes{$prod} = $notes; }

  8. Defining the Output Format format STDOUT_TOP = Code Price Notes ---- ------- -------- . format STDOUT = @>>> ^###.## ^<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< $prod, $cost, $note ~~ ^<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< $note .

  9. Writing the New Report open COST, "<cost.txt" or die "open cost.txt: $!"; while ($line = <COST>) { next unless $line =~ m/^\d/; ($prod, $cost) = unpack 'A4 @20 A7', $line; $cost *= $prod_margin{$prod} || 1.10; $note = $prod_notes{$prod} || 'n/a'; write; # using format with $prod, $cost and $note }

  10. Mission Accomplished! Code Price Notes ---- ------- -------- 1201 450.00 Special offer for limited period only 1202 1027.00 n/a 1203 493.90 n/a

  11. Changeis the only Constant Your new mission...

  12. “Cache the data for other uses!” dbmopen(%price_cache, "price_cache", 0644) or die …; while ($line = <COST>) { . . . write; # using format with $prod, $cost and $note $price_cache{$prod} = "$cost $note"; }

  13. “Update the Prices in a Database!” use DBI; $db = DBI->connect('dbi:ODBC:PRICE', 'user', 'password', { RaiseError => 1 }); $upd = $db->prepare('UPDATE prices SET price=? WHERE prod=?'); $ins = $db->prepare('INSERT INTO prices(prod,price) VALUES (?,?)'); while ($line = <COST>) { . . . $rows = $upd->execute($price, $prod); $ins->execute($prod,$price) if $rows == 0; } $db->commit;

  14. “Now get Cost Data from a Database!” • Original Code open COST, "<cost.txt" or die "open cost.txt: $!"; while ($line = <COST>) { next unless $line =~ m/^\d/; ($prod, $cost) = unpack 'A4 @20 A7', $line; . . . • New Code $costs = $cost_db->prepare('SELECT prod,cost FROM costs'); $costs->execute; while ( ($prod, $cost) = $costs->fetchrow_array ) { . . .

  15. What Is the Perl DBI? • The standard Database Interface for Perl • “A perl module and specification that defines a consistent database interface independent of the actual database being used”

  16. Why the Perl DBI? • Once upon a time… • One language, many database interfaces • A vision of the future... “DBperl” • Talk, talk, talk - the dbperl-interest mailing list • Perl 5 - A new way • Modules and Objects. The DBI is born. • The future is now… • ODBC, Oracle, Informix, Ingres, mSQL, mysql, DB2, Solid,Sybase, Postgress,Quickbase,Empress,Fulcrum, ...

  17. Making simple things easyand difficult things possible • Goals • Be simple to use for simple applications • Have sufficient flexibility to accommodate unusual functionality and non-SQL databases • Conform to applicable standards (ODBC etc.) • Enable the creation of database-independent Perl scripts without being limited to the lowest functionality • Be free. • A ‘higher-level’ interface than ODBC/JDBC

  18. Getting Technical... for the techies...

  19. Under the Hood • DBI defines and implements an interface • Driver modules do much of the real work • DBI provides default methods, functions, tools etc for drivers • Not limited to the lowest common denominator - mechanism provided for driver specific extensions • Designed and built for speed • Valuable detailed call tracing/debugging built-in

  20. A Picture is Worth... Perl Application DBI Module DBD::Oracle DBD::Informix DBD::Other Oracle Server Informix Server Other Server

  21. State of the Nation • DBI builds and runs on many systems • Unix, Windows 95, Windows NT, VMS etc • Many drivers exist • more in development • Merging the ODBC/JDBC ‘inheritance’ • data types, meta-data etc • Specifying the unspecified • Documenting the undocumented

  22. What Next? • SQL for Non-SQL data sources • Networking for Non-Networked data sources • Template driver for command line interfaces • Data types, especially date/time/interval • Non-blocking (method calls return at once) • Multi-threading • Binding In/Out Variables • Binding Arrays

  23. Comparing DBI and Alternatives(Attempting the Impossible!) “Power” DBI and Drivers Sybase::DBlib Win32::ODBC Native API ODBC/ JDBC and drivers Precompilers Command Line TCL (oratcl, sybtcl) “Effort” Please note: This chart is correct only for some values of correct!

  24. So why use the Perl DBI? • Because... • It delivers what it promises • It’s here, there and everywhere • It’s fast, flexible and well proven • It’s free, with source • Commercial support is available • It has a large user base and a strong future

  25. So What?

  26. Success Stories in Industry • Large Scale Data Migration • by Michael Peppler • Database Interfaced Web Pages • by Frank San Filippo • The British TelecomCall Management Information Service • by Tim Bunce

  27. Too Good to Be True? • Just three examples of many • Thousands of Perl DBI developers around the world • Millions of users of DBI powered web sites • Oracle and Apache web servers with built-in Perl and DBI • Commercial support available from The Perl Clinic

  28. And finally... • “We have replaced all Netscape JavaScript code with Perl DBI/DBD to Informix” - Del Simmons, Cox Interactive Media. • “I have found performance and stability to be exceptional” - Stuart Huges, PECC. • “Perl and DBI saved our butt. The tool we came closest to purchasing was SQR but it just doesn’t have the flexibility and power of Perl/DBI.” - Jared Still, RxNet. • “I have been able to recommend the Perl/DBI route to a number of our clients and all of them have been pleased with the results” - Paul Rubenis, Ulysses Telemedia Networks

  29. The end. Till next year...

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