Oliver Kurowski discusses various transformation functions available in CouchDB for handling JSON documents and views. He provides examples of 'shows' and 'lists' functions that can be used to manipulate and display data in specific formats during request processing. The document includes practical implementations and usage scenarios for these transformation capabilities.

1. COUCHDB
<- Watch the car Oliver Kurowski, @okurow

2. Who am I
 Oliver Kurowski
 Degree in Computer Science Beuth School of applied Sciences Berlin
 First Computer: Apple II 1983
 Since 2003: kw automotive GmbH
 Write articles in Magazines
 2012: Book „CouchDB mit PHP“ (www.CouchDBmitPHP.de)
 Twitter: @okurow
 Mail: oliver@thinkcouchdb.com
Oliver Kurowski, @okurow

3. TRANSFORMATIONS
Oliver Kurowski, @okurow

4. Transformation Functions
Documents are JSON objects
Results of views are also JSON objects
CouchDB can transfrom those JSON Objects on server side.
Shows: Transformation for documents
Lists: Transformation for views
Shows and lists are performed during request, results are not stored (like views).
Oliver Kurowski, @okurow

5. Shows:Transform Documents I
Oliver Kurowski, @okurow

6. Shows:Transform Documents I
Oliver Kurowski, @okurow

7. Shows:Transform Documents I
Oliver Kurowski, @okurow

8. Shows:Transform Documents I
Oliver Kurowski, @okurow

9. Shows:Transform Documents I
Oliver Kurowski, @okurow

10. Shows:Transform Documents I
Data document (JSON): Show function in a design doc:
{ “shows“: {
“_id“: “1“, “toHTML“:“function(doc,req) {
“make“: “Audi“, var outS=‘‘;
“model“: “A3“, outS=‘<b>‘+doc.maker+‘ ‘+doc.model+‘</b><br>`;
“year“: 2000, outS+=‘Year of Prod.: ‘+doc.year+‘<br>‘;
“price“: 5.400 outS+=‘Price: ‘+doc.price;
} return outS; }“
}
Result of _show/toHTML/1 :
Audi A3
Year of Prod.: 2000
Price: 5.400
Oliver Kurowski, @okurow

11. Shows:Transform Documents II
Data document (JSON):
{
“_id“: “1“,
“author“: “Oliver Kurowski“,
“headline“: “CouchDB is great“,
“body“: “CouchDb is a great database for schemeless data“ ,
“comments“: [ {“name“: “John“, “text“: “Yes, it really is“},
{“name“: “Jane“, “text“: “What about couchbase?“} ]
}
“shows“: {
“headline“:“function(doc,req) {
var comments=0;
if (doc.comments) { comments=doc.comments.length };
var outS=‘<b>‘ + doc.headline + ‘</b> (‘ + comments + ‘ comments)`;
return outS; }“,
“detail“:“function(doc,req) {
var outS=‘<b>‘ + doc.headline + ‘</b><br>`;
outS+= doc.body + ‘<br>`;
if (doc.comments && doc.comments.length>0) {
outS+= ‘comments:<br>`;
for (var curComment in doc.comments) {
outS+=doc.comments[curComment].name+‘:<br>`;
outS+=doc.comments[curComment].text+‘<br>`;
}
}
return outS; }“
}
Oliver Kurowski, @okurow

12. Shows:Transform Documents II
Data document (JSON):
{
“_id“: “1“,
“author“: “Oliver Kurowski“,
“headline“: “CouchDB is great“,
“body“: “CouchDb is a great database for schemeless data“ ,
“comments“: [ {“name“: “John“, “text“: “Yes, it really is“},
{“name“: “Jane“, “text“: “What about couchbase?“} ]
}
“shows“: {
“headline“:“function(doc,req) {
var comments=0;
if (doc.comments) { comments=doc.comments.length };
var outS=‘<b>‘ + doc.headline + ‘</b> (‘ + comments + ‘ comments)`;
return outS; }“,
“detail“:“function(doc,req) {
var outS=‘<b>‘ + doc.headline + ‘</b><br>`;
outS+= doc.body + ‘<br>`;
if (doc.comments && doc.comments.length>0) {
outS+= ‘comments:<br>`;
for (var curComment in doc.comments) {
outS+=doc.comments[curComment].name+‘:<br>`;
outS+=doc.comments[curComment].text+‘<br>`;
}
}
return outS; }“
}
Oliver Kurowski, @okurow

13. Shows:Transform Documents II
Data document (JSON):
{
“_id“: “1“,
“author“: “Oliver Kurowski“,
“headline“: “CouchDB is great“,
“body“: “CouchDb is a great database for schemeless data“ ,
“comments“: [ {“name“: “John“, “text“: “Yes, it really is“},
{“name“: “Jane“, “text“: “What about couchbase?“} ]
}
“shows“: {
“headline“:“function(doc,req) {
var comments=0;
if (doc.comments) { comments=doc.comments.length };
var outS=‘<b>‘ + doc.headline + ‘</b> (‘ + comments + ‘ comments)`;
return outS; }“,
“detail“:“function(doc,req) {
var outS=‘<b>‘ + doc.headline + ‘</b><br>`;
outS+= doc.body + ‘<br>`;
if (doc.comments && doc.comments.length>0) {
outS+= ‘comments:<br>`;
for (var curComment in doc.comments) {
outS+=doc.comments[curComment].name+‘:<br>`;
outS+=doc.comments[curComment].text+‘<br>`;
}
}
return outS; }“
}
Oliver Kurowski, @okurow

14. Shows:Transform Documents II
Data document (JSON):
{
“_id“: “1“,
“author“: “Oliver Kurowski“,
“headline“: “CouchDB is great“,
“body“: “CouchDb is a great database for schemeless data.“ ,
“comments“: [ {“name“: “John“, “text“: “Yes, it really is“},
{“name“: “Jane“, “text“: “What about couchbase?“} ]
}
“shows“: {
“headline“:“function(doc,req) { Result of _show/headline/1 :
var comments=0; CouchDB is great (2 comments)
if (doc.comments) { comments=doc.comments.length };
var outS=‘<b>‘ + doc.headline + ‘</b> (‘ + comments + ‘ comments)`;
return outS; }“,
“detail“:“function(doc,req) {
var outS=‘<b>‘ + doc.headline + ‘</b><br>`;
outS+= doc.body + ‘<br>`;
if (doc.comments && doc.comments.length>0) {
outS+= ‘<hr>Comments:<br>`;
for (var curComment in doc.comments) {
outS+=doc.comments[curComment].name+‘:<br>`;
outS+=doc.comments[curComment].text+‘<br>`;
}
}
return outS; }“
}
Oliver Kurowski, @okurow

15. Shows:Transform Documents II
Data document (JSON):
{
“_id“: “1“,
“author“: “Oliver Kurowski“,
“headline“: “CouchDB is great“,
“body“: “CouchDb is a great database for schemeless data.“ ,
“comments“: [ {“name“: “John“, “text“: “Yes, it really is“},
{“name“: “Jane“, “text“: “What about couchbase?“} ]
}
“shows“: {
“headline“:“function(doc,req) { Result of _show/headline/1 :
var comments=0; CouchDB is great (2 comments)
if (doc.comments) { comments=doc.comments.length };
var outS=‘<b>‘ + doc.headline + ‘</b> (‘ + comments + ‘ comments)`;
return outS; }“,
“detail“:“function(doc,req) {
var outS=‘<b>‘ + doc.headline + ‘</b><br>`;
Result of _show/detail/1 :
outS+= doc.body + ‘<br>`; CouchDB is great
if (doc.comments && doc.comments.length>0) { CouchDb is a great database for schemeless data.
outS+= ‘<hr>Comments:<br>`;
for (var curComment in doc.comments) { Comments:
outS+=doc.comments[curComment].name+‘:<br>`; John:
outS+=doc.comments[curComment].text+‘<br>`; Yes, it really is
} Jane:
} What about couchbase?
return outS; }“
}
Oliver Kurowski, @okurow

16. The Request Object
Shows and lists can access the Request Object containing:
(the most interesting)
Info: Informations about the Database
Id: called document ID (null, if not given)
requested
_path: The request in parts (divided by /) as Array
headers: Header, sent from the client
userCTX: Information about the user, usefull for access limitations!
query: Parameters of the call
The field req.query allows the use of own parameters that can be used in a
show/list function.
F.e: _show/toHTML/1?showPrice=true
handled in the show function: if(req.query.showPrice==true) { ….}
Oliver Kurowski, @okurow

17. Shows:Talking Parrots
Data documents : Design document :
{ {
“_id“: “lora“, “_id“: “_design/parrot“,
“name“: “Lora LoL“, “shows{
“owner“: “Emily“, "introduce": "function(doc,req) {
“color“: [“red“ , “#ff0000“ ] , var outS='';
“languages“: [ “english“ ] if(doc) { // doc with id in database found
} outS+='<font color='+doc.color[1]+'>'+doc.name
+' belongs to '+doc.owner+'</font>';
{ if(req.query.say) {
“_id“: “polly“, if(doc.languages) {
“name“: “Polly Poll“, outS+=' and says: '+req.query.say;
“owner“: “Ernest“, }else{
“color“: [“blue“ , “#0000ff“ ], outS+='tweet';
“languages“: [ “english“ ] }
} }
} else { // no doc found
if(req.path[5]!=undefined) { // no id given
{ outS+='I dont know '+req.path[5];
“_id“: “agnus“, }else{
“name“: “Agnus Angry“, outS+='which parrot?';
“owner“: “Ernest“, }
“color“: [“grey“ , “#cococo“ ] }
} return outS; }“
}
}
Oliver Kurowski, @okurow

18. Shows: Talking Parrots
http://localhost:5984/parrots/_design/parrot/_show/introduce/
->which parrot?
http://localhost:5984/parrots/_design/parrot/_show/introduce/polly
->Polly Poll belongs to Ernest
http://localhost:5984/parrots/_design/parrot/_show/introduce/pollx
->I dont know pollx
http://localhost:5984/parrots/_design/parrot/_show/introduce/lora?say=Hello
->Lora Loll belongs to Emily and says: Hello
http://localhost:5984/parrots/_design/parrot/_show/introduce/agnus?say=Hello
->Agnus Angry belongs to Ernest tweet
Oliver Kurowski, @okurow

19. List:Transform view results I
Oliver Kurowski, @okurow

20. List:Transform view results I
Oliver Kurowski, @okurow

21. List:Transform view results I
Oliver Kurowski, @okurow

22. List:Transform view results I
Oliver Kurowski, @okurow

23. List:Transform view results I
Oliver Kurowski, @okurow

24. List:Transform view results I
Result of a View byPrice: A simple list function:
{"total_rows":5,"offset":0, “lists“: {
"rows":[ “asLI “:“function(head,req) {
{"id":"1","key":5.400,"value":“Audi-A3- start({'code':200,'headers':{'Content-Type':'text/html'}});
2000“}, {"id":"2","key":9.000,"value":“VW-Golf- while(row=getRow()) {
2008“}, {"id":"3","key":12.000,"value":“VW-Polo- send(‘<li>‘+row.value+‘ :‘ +row.key+‘</li>‘);
2010“}, {"id":"4","key":15.000,"value":“VW-Golf- }
2009“}, {"id":"5","key":16.000,"value":“Audi-A4- }“
2009“} ]} }
result from _list/asLi/byPrice :
• Audi-A3-2000 : 5.400
• VW-Golf-2008 : 9.000
• VW-Polo-2010 : 12.000
• VW-Golf-2009 : 15.000
• Audi-A4-2009 : 16.000
- All arguments from a view can also be used in a list call
(startkey, endkey, skip, limit etc)
- Like Shows, you have access to the request Object with all ist possibilities.
Oliver Kurowski, @okurow

25. List:Transform view results II
Different headers can be sent
“lists“: {
“asXML “:“function(head,req) {
start({'code':200,'headers':{'Content-Type':'application/xml'}});
var xmlS=‘<cars>‘;
while(row=getRow()) {
xmlS+=‘<car id=‘ + row.id + ‘>‘+row.value+‘ :‘ +row.key+‘</car>‘);
}
xmlS+=‘</cars>‘;
return xmlS;
}“
}
result from _list/asXML/byPrice :
<cars>
<car id=‘1‘>Audi-A3-2000 : 5.400</car>
<car id=‘2‘>VW-Golf-2008 : 9.000</car>
<car id=‘3‘ >VW-Polo-2010 : 12.000</car>
<car id=‘4‘>VW-Golf-2009 : 15.000</car>
<car id=‘5‘>Audi-A4-2009 : 16.000</car>
</cars>
Oliver Kurowski, @okurow

26. http://apache.couchdb.org
Irc: #couchdb
Q (&A?)
Oliver Kurowski, @okurow