I'm writing a Couchdb _design document for the SQL command below:
SELECT NVL(MAX(NVL(VERSION,0)),0)+1 FROM pricelistdocs WHERE
PRICE_LIST_ID = ? AND DELETION_FLAG = 0;
I came up with a _design view function below while run and return values but I doubt if the correct and fulfills expectation of the above SQL command.
function(doc){
if(doc.PRICE_LIST_ID == "110011" && doc.DELETION_FLAG == "0" ){
emit(doc._id, doc.VERSION);
}
}
Please how can I add the NVL() and MAX function to my _design view document above.
Any infortiom or clue is appreciated. Thank you for your time.
You can write your own NVL function by checking for the existance of a field and returning 0 if it does not exist.
For the max functionality, you have to add a reduce function to your view. If you just want to get the maximum, "reduce": "_max" will do, which is a built in reduce function.
Related
I am brand new to noSQL, couchDB, and mapreduce and need some help.
I have the same question discussed here {How to use reduce in Fauxton} but do not understand the answer:(.
I have a working map function:
function (foo) {
if(foo.type == "blog post");
emit(foo)
}
which returns 11 individual documents. I want to modify this to return foo.type along with a count of 1.
I have tried:
function (doc) {
if(doc.type == "blog post");
return count(doc)
}
and "_count" from the Reduce panel, but clearly am doing something wrong as the View does not return anything.
Thanks in advance for any assistance or guidance!
In Fauxton, the Reduce step is kind of awkward and unintuitive to find.
Select _count in the "Reduce (optional)" popup below where you type
in your Map.
Select "Save Document and then Build Index". That will display your
map results.
Find the "Options" button at the top next to a gears icon. If you see a
green band instead, close the green band with the X.
Select Options, then the "Reduce" check-circle. Select Run Query.
Map
So when you build a map function, you are literally creating a dictionnary or map which are key:value data structures.
Your map function should emit keys that you will query. You can also emit a value but if you intend to simply get the associated document, you don't have to emit any values. Why? Because there is a query parameter that can be used to return the document associated (?include_docs=true).
Reduce
Then, you can have reduce function which will be called for every result with the same keys. Every result with the same key will be processed through your reduce function to reduce the value.
Corrected example
So in your case, you want to map document the document per type I suppose.
You could create a function that emit documents that have the type property.
function(doc){
if(doc.type)
emit(doc.type);
}
If you query this view, you will see that the keys of each rows will be the type of the document. If you choose the _count reduce function, you should have the number of document per types.
When querying the view, you have to specify : group=true&reduce=true
Also, you can get all the document of type blog postby querying with those parameters : ?key="blog post"
I have created a function in SSJS Library. Because I use it in more than one XPages.
When I call this function behind a button I cannot see the value in the field
If I print it out I can see the value at the Admin Console but cannot see it in the form Even if I get page with full refreshed.
Actually my another question is.. is it possible to compare notesXSPDocument and NotesDocument. Maybe someoen can say that what is the best way for that?
function deneme(document1:NotesXSPDocument,otherDocfromOtherDatabase:NotesDocument)
{
//do staff here
if (document1.getItemValueString("field1")==otherDocfromOtherDatabase.getItemValueString("field2"))
{ //do some staff here...
document1.replaceItemValue("fieldName","FieldValue");}
}
You can compare item values from Document and XSPDocument, just be careful with the type you are comparing.
In your code you are comparing 2 javascript strings with == operator.
The code seems to be OK, just remember to save the document1 after the changes and maybe check that the items have some value.
var valueFromXspDoc = document1.getItemValueString("field1");
var valueFromDoc = otherDocfromOtherDatabase.getItemValueString("field2");
if (valueFromXspDoc && valueFromDoc && (valueFromXspDoc === valueFromDoc)) {
// stuff here...
document1.replaceItemValue("fieldName","FieldValue");
document1.save();
}
Don not compare it with == sign. A better way is to document1.getItemValueString("field1").equals(otherDocfromOtherDatabase.getItemValueString("field2"))
I want to be able query the couchdb between dates, I know that this can be done with startkey and endkey (it works fine), but is it possible to do query for example like this:
SELECT *
FROM TABLENAME
WHERE
DateTime >= '2011-04-12T00:00:00.000' AND
DateTime <= '2012-05-25T03:53:04.000'
AND
Status = 'Completed'
AND
Job_category = 'Installation'
Generally-speaking, establishing indexes on multiple fields grows in complexity as the number of fields increases.
My main question is: do Status and Job_category need to be queried dynamically too? If not, your view is simple:
function (doc) {
if (doc.Status === 'Completed' && doc.Job_category === 'Installation') {
emit(doc.DateTime); // this line may change depending on how you break up and emit the datetimes
}
}
Views are fairly cheap, (depending on the size of your database) so don't be afraid to establish several that cover different cases. I would expect something like Status to have predefined list of available options, as oppposed to Job_category which seems like it could be more related to user input.
If you need those fields to be dynamic, you can just add them to the index as well:
function (doc) {
emit([ doc.Status, doc.Job_category, doc.DateTime ]);
}
Then you can use an array as your start_key. For example:
start_key=["Completed", "Installation", ...]
tl;dr: use "static" views where you have a predetermined list of values for a given field. while possible to query "dynamic" views with multiple fields, the complexity grows very quickly.
suppose i have the following data in my database:
[1,2],[2,1],[1,3],[3,1]...
were the numbers represent the a and b values of the formula a*x+b
what i now want is a query that returns the difference to a given point x,y.
for example: the point [2,6] is given. i want my query to return
[1,2] = -2 (1*2+2=4 4-6=-2)
[2,1] = -1 (2*2+1=5 5-6=-1)
[1,3] = -1 (1*2+3=5 4-6=-1)
[3,1] = 1 (3*2+1=7 7-6=-1)
I know how to do this in SQL but the data is already in a couchdb. I'm quite new to the NoSQL world and was wondering if something like this would be possible in couchdb.
what you can do is to use the standard MapReduce functionality of CouchDB.
Map is function you put in a view, which finds your data. You can have various criteria how to locate the docs you need. Next, if you specify so in the query with reduce=true, a reduce function is executed on each document that matched the map condition. You can use JavaScript to perform various operations on the document's values.
In your case, the map can look something like this:
function(doc) {
if(doc.a && doc.b) {
emit(doc._id,[doc.a, doc.b]);
}
}
then, the reduce gets called, like this:
function(keys, values, rereduce) {
var res;
//do something with values...
return res;
}
In your case keys will be list of document ID's and values will be the array of your a & b fields.
When you call the MapReduce (depending what method you use to access the DB), you should specify reduce=true.
Good resources on MapReduce (and on Views, Sorting and List funtions) are:
http://guide.couchdb.org/draft/views.html
http://www.slideshare.net/okurow/couchdb-mapreduce-13321353
Another way to go is to use a list function on the Map result, if you want to output the result in HTML. A good reason to use List function is that you can pass arguments to it with querystring, in your case it may be the point for which you want to calculate distances.
For detailed description on List functions, have a look here:
http://guide.couchdb.org/draft/transforming.html
Hope this helps.
I'm stumbling a bit with my CouchDB knowledge.
I have a database of content that is tagged with an array of tags and has a created date.
I want to create a view that pulls a limited number of newest stories tagged with a specific tag.
For example, the newest 6 stories tagged "Business."
Ran across this question, which seems to get me almost to where I need to go, but I'm missing one key element, which I think is how to craft the query string to sort by one key while searching by the other.
Here's my map function.
function(doc) {
if (doc.published == "yes" && doc.type == "news") {
for (var i = 0; i < doc.tags.length; i++) {
if (doc.tags[i]) {
emit([doc.created, doc.tags[i]], doc);
}
}
}
}
So how do I query that view for a all documents tagged "Business" that are the newest documents based on created.
The created attribute is a date sortable format.
First, I would switch the order of your emit:
emit([doc.tags[i], doc.created]);
(leave out doc as well, you can just add include_docs=true to get the entire document, and your view won't take up so much disk-space in the process)
Now you can query for the all the stories tagged as "Business" by using the following querystring:
startkey=["Business"]&endkey=["Business",{}]
You'll get all the documents with the tag business, and they'll be sorted by date.
This takes advantage of view collation, which basically is the rules governing how indexes are sorted/queried. For complex keys like this, the sorting is done for each item of the array separately. (ie. the first key is sorted first, the second key is sorted second, etc) This is why the order matters, as you must always move from left to right when querying a view index.
If you want the 6 most recent, your querystring will need to change:
descending=true&limit=6&endkey=["Business"]&startkey=["Business",{}]
NOTICE You need to swap the startkey/endkey values, due to how the descending parameter works. See the View reference page on the wiki for further explanation.
OK, I think I figured this out, but I'm not quite certain I fully understand it.
I found this story about complex keys and searching and sorting.
My map function looks like this:
function(doc) {
if (doc.published == "yes" && doc.type == "news") {
for (var i = 0; i < doc.tags.length; i++) {
if (doc.tags[i]) {
emit([doc.tags[i], doc.created], doc);
}
}
}
}
And to query and sort using it, the query looks like this.
http://localhost:5984/database/_design/story/_view/tagged?limit=10&startkey=["Business"]&endkey=["Business",{}]&descending=false
I'm getting the results I want, but I'm not entirely certain I understand it all.