> Thus, I suggest that we implement MERGE as a separate operation backed by > putIfAbsent operation, while INSERT will be implemented via put.
Sorry, of course I meant that MERGE has to be put-based, while INSERT has to be putIfAbsent-based. 2016-07-20 12:30 GMT+03:00 Alexander Paschenko <alexander.a.pasche...@gmail.com>: > Hell Igniters, > > In this thread I would like to share and discuss some thoughts on DML > operations' implementation, so let's start and keep it here. Everyone > is of course welcome to share their suggestions. > > For starters, I was thinking about semantics of INSERT. In traditional > RDBMSs, INSERT works only for records whose primary keys don't > conflict with those of records that are already persistent - you can't > try to insert the same key more than once because you'll get an error. > However, semantics of cache put is obviously different - it does not > have anything about duplicate keys, it just quietly updates values in > case of keys' duplication. Still, cache has putIfAbsent operation that > is closer to traditional notion of INSERT, and H2's SQL dialect has > MERGE operation which corresponds to semantics of cache put. Thus, I > suggest that we implement MERGE as a separate operation backed by > putIfAbsent operation, while INSERT will be implemented via put. > > And one more, probably more important thing: I suggest that we create > separate class Update and corresponding operation update() in > IgniteCache. The reasons are as follows: > > - Query bears some flags that are clearly redundant for Update (page > size, locality) > - query() method in IgniteCache (one that accepts Query) and query() > methods in GridQueryIndexing return iterators. So, if we strive to > leave interfaces unchanged, we still will introduce some design > ugliness like query methods returning empty iterators for certain > queries, and/or query flags that indicate whether it's an update query > or not, etc. > - If some Queries are update queries, then continuous queries can't be > based on them - more design-wise ugly checks and stuff like that. > - I'm pretty sure there's more I don't know about. > > Comments and suggestions are welcome. Sergi Vladykin, Dmitry > Setrakyan, your opinions are of particular interest, please advise. > > Regards, > Alex
