Thanks for the pointer, Shawn. It, definitely, is useful. I am wondering if you could retrieve minDid from the solr rather than storing it externally. Max id from Solr index and max id from DB should define the lower and upper thresholds, respectively, of the delta range. Am I missing something?
--shashi On Wed, Sep 22, 2010 at 6:47 PM, Shawn Heisey <s...@elyograg.org> wrote: > On 9/22/2010 1:39 AM, Shashikant Kore wrote: > >> Hi, >> >> I'm using DIH to index records from a database. After every update on >> (MySQL) DB, Solr DIH is invoked for delta import. In my tests, I have >> observed that if db updates and DIH import is happening concurrently, >> import >> misses few records. >> >> Here is how it happens. >> >> The table has a column 'lastUpdated' which has default value of current >> timestamp. Many records are added to database in a single transaction that >> takes several seconds. For example, if 10,000 rows are being inserted, the >> rows may get timestamp values from '2010-09-20 18:21:20' to '2010-09-20 >> 18:21:26'. These rows become visible only after transaction is committed. >> That happens at, say, '2010-09-20 18:21:30'. >> >> If Solr is import gets triggered at '18:20:29', it will use a timestamp of >> last import for delta query. This import will not see the records added in >> the aforementioned transaction as transaction was not committed at that >> instant. After this import, the dataimport.properties will have last index >> time as '18:20:29'. The next import will not able to get all the rows of >> previously referred trasaction as some of the rows have timestamp earlier >> than '18:20:29'. >> >> While I am testing extreme conditions, there is a possibility of missing >> out >> on some data. >> >> I could not find any solution in Solr framework to handle this. The table >> has an auto increment key, all updates are deletes followed by inserts. >> So, >> having last_indexed_id would have helped, where last_indexed_id is the max >> value of id fetched in that import. The query would then become "Select id >> where id>last_indexed_id.' I suppose, Solr does not have any provision >> like >> this. >> >> Two options I could think of are: >> (a) Ensure at application level that there are no concurrent DB updates >> and >> DIH import requests going concurrently. >> (b) Use exclusive locking during DB update >> >> What is the best way to address this problem? >> > > Shashi, > > I was not solving the same problem, but perhaps you can adapt my solution > to yours. My main problem was that I don't have a modified date in my > database, and due to the size of the table, it is impractical to add one. > Instead, I chose to track the database primary key (a simple autoincrement) > outside of Solr and pass min/max values into DIH for it to use in the SELECT > statement. You can see a simplified version of my entity here, with a URL > showing how to send the parameters in via the dataimport GET: > > http://www.mail-archive.com/solr-user@lucene.apache.org/msg40466.html > > The update script that runs every two minutes gets MAX(did) from the > database, retrieves the minDid from a file on an NFS share, and runs a > delta-import with those two values. When the import is reported successful, > it writes the maxDid value to the minDid file on the network share for the > next run. If the import fails, it sends an alarm and doesn't update the > minDid. > > Shawn > >
