We are experiencing a sudden and strange issue with our Azure Search indexer. We had an index (2015-02-28-preview version) with corresponding datasource and indexer based on a table of a SQL Azure v12 database. Change tracking was enabled and changes were properly forwarded in the index. A couple of days ago, our attention was drawn by the fact that last changes in the database were no more properly replicated to the index. Being in a development phase, this index was frequently rebuilt by developers and nobody has noticed when exactly things started to go wrong.
In the Azure portal, the index is displayed in red color with an error message stating we have a duplicate column in the datasource...("Datasource contains multiple columns with the same name 'ProductId'") which is false. We cleaned the database and tried several things but could not find any duplicate column. As for today, the situation is the following :
1/ After deleting and recreating everything (index, indexer and datasource) the index is filled with the 2000 documents present in the SQL table
2/ The index is full and can be queried without any issue, though it still shows up in red with the "duplicate column" error message
3/ Due to this error, we cannot manually force a new indexation from the azure portal
4/ In order to reflect changes of the indexed table, we have to run again the script which deletes index, indexer and datasource and re-creates everything. After running this script .. we're back at step 1 above (index queryable, but in error state and cannot be updated without drop/recreate).
This problem seems to have occurred all of a sudden without any change on our side, as if there had been a server-side version change. Are there any newer release of the Azure Search Rest APIs available ? Has anyone ever encountered the same issue or has any hints on things we could check ?
Thanks for your help shedding some light on what may be broken here,
Problem fixed thanks to Eugene investigations. He discovered a bug in the C# code used to generate the datasource : a casing difference between a “ProductId” column in the database and a “ProductID” field in the index.
We fixed the misspelling and the issue is gone. Microsoft support said that they'll "fix the issue in the coming weeks" : The same code used to work properly (and is still working properly on the first run), so it looks like the indexing process has somehow become more case sensitive than before.