See what WITH CONNECTION can do for you when working with REST data sources
I was approached by a colleague with a simple but recurrent question, how can I use for…while loops in conjunction with the REST connector, and how can we make it work with the connection library that comes with Qlik Sense.
A few months ago I shared a “hack” so we can do loops in our scripts as we do with QlikView, activating Legacy Mode will make connection library optional, please remember that there are a bunch of good reasons for not do that. “With connection” is a great solution for those of you who don’t want or just can’t activate Qlik Sense Desktop to work in Legacy Mode but still need to loop through several URLs to get complete data.
Let’s do a quick example.
We need to load data from an online data source, we have a URL to connect to the data that contains the ID of each one of the elements that we would like to load into our app.
We have a list of 100 alphanumeric elementIDs and we need to make sure we load them all. Using our REST connector, we could easily connect to the online data source and extract the data, but we faced the issue of how to make to connection loop trough a series of items.
In our example we have an inline table that contains each one of the ID numbers of the elements we want to read in the REST connector, and we need to pass that parameter to the connection URL below.
LIB CONNECT TO 'REST';
ElementsToLoad:
Load * inline [
ElementID
12fa91
1sy293
h13d13
…
];
Let j=0;
for j = 0 to 99
Let vElementID = peek('ElementID', $(j), 'Teams');
RestConnectorMasterTable:
SQL SELECT
fields
FROM "datad")
FROM JSON (wrap on) "root" PK "__KEY_root"
WITH CONNECTION(Url "https://www.domain.com/element?key=$(vElementID)/more_stuff/");
NEXT j;
DROP TABLE RestConnectorMasterTable;
exit Script;
After the inline statement, we loop over the REST connection 100 times, one time for each row of the inline table, I know we have 100 rows so I'm hard coding that number but if you don't know how long your table is you should check that before and store it in a variable.
Lately, using "With Connection" we have access to the data source URL so we can expand my variable "vElementID" containing the necessary ID for the connection to work.
What I have had to do in the past is make a first call in your load script to get the Authentication Key. Save that in a variable.
Then in your With Connection you use that variable for the key value.
In the REST Connector itself you enter the username and password into the properties for that connection. I had an admin login that I used that never changed in my situation.
I don't know enough about your situation to say if this will work for you or not.
This was really a terrific article and exactly what I was looking for however it isn't quite working. Instead of inline load I'm loading from a table previously generated and trying to loop through the data in the table. I see the new data generated but it is not incrementing it simply is grabbing the same data however many times I specify in the statement for x( 'for j = 0 to x' ).
hostId is a previously generated table with Ids of hosts I'm trying to iterate through with my connection url.
I know it is working because if I substitute in hard coded 0,1,2 as "a". It pulls three different hostIds. Using the scripted example above to loop only brings back the same hostID 3 times.
LIB CONNECT TO 'GETDETAILS';
for a = 0 to 2
Let vHostDetail = peek('hostId', a);
RestConnectorMasterTable: SQL SELECT "__KEY_root", (SELECT "ip", "mac", "id", "__KEY_host", "__FK_host", (SELECT "__KEY_fields", "__FK_fields", (SELECT "timestamp" AS "timestamp_u38", "value" AS "value_u38", "__FK_matched_fingerprints" FROM "matched_fingerprints" FK "__FK_matched_fingerprints"), (SELECT "timestamp" AS "timestamp_u76", "value" AS "value_u76", "__FK_engine_seen_packet" FROM "engine_seen_packet" FK "__FK_engine_seen_packet") FROM "fields" PK "__KEY_fields" FK "__FK_fields") FROM "host" PK "__KEY_host" FK "__FK_host"), (SELECT "__KEY__links", "__FK__links", (SELECT "href", "templated", "__FK_self" FROM "self" FK "__FK_self") FROM "_links" PK "__KEY__links" FK "__FK__links") FROM JSON (wrap on) "root" PK "__KEY_root"
@beam I guess it's because you load over the same table "RestConnectorMasterTable" that gets refreshed on every new host id. You should probably do a CONCATENATE.
Hmm I don't think so the table I'm loading from is 'hosts' in a previous script. I can hardcode the 'a' value and pull back any of the IDs in the table 'hosts' just fine. Sorry if I'm not fully understanding your explanation I'm still VERY new to qlik.
[hosts]: LOAD [hostId] AS [hostId], __KEY_hosts RESIDENT RestConnectorMasterTable WHERE NOT IsNull([__KEY_hosts]); JOIN(hosts) [_links]: LOAD [__KEY__links] AS [__KEY__links], [__FK__links] AS [__KEY_hosts] RESIDENT RestConnectorMasterTable WHERE NOT IsNull([__FK__links]); JOIN(hosts) [self]: LOAD [href] AS [href], [templated] AS [templated], [__FK_self] AS [__KEY__links] RESIDENT RestConnectorMasterTable WHERE NOT IsNull([__FK_self]);
@sergeyko thanks but still doesn't work. It is weird if I just loop the top part it pulls the three urls just fine. Once I use the url inside the "with connection" statement and loop after my sql select it only takes the first url.
