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It is interesting, but what I really need in the JSON functionality of PG is some internal representation that will allow fast and efficient exploration of the
by DEinspanjer 14y ago
It is interesting, but what I really need in the JSON functionality of PG is some internal representation that will allow fast and efficient exploration of the JSON blob within the query. i.e. being able to refer to a single attribute within the select/where/groupby clauses without having to pay the toll of serde every time.
- jerrysievert 14y agoexactly. calling the find_in_obj() function can get fairly expensive, especially given the need to execute JSON.parse() for every call. there is definitely a lot of room for improvement in the postgres native JSON toolkit. i am hoping that building this exposes more of those issues and helps move it forward.
- disbelief 14y agoBut the same is true for MongoDB. If you're querying an attribute of a document that isn't indexed, Mongo has to scan all of the Documents in the collection for it. The solution to this is to have additional indexes on any attributes you want to be able to query by. This holds true both in Mongo and this Postgres implementation.
- rarrrrrr 14y agoI haven't tried it, but I think you would be able to use a PostgreSQL functional index (i.e. indexing the result of a function call to extract a particular bit of data from the JSON.) http://www.postgresql.org/docs/9.1/interactive/indexes-expressional.html http://www.postgresql.org/docs/9.1/interactive/indexes-expre...
- rosser 14y agoI was just coming here to say exactly this. You could also use a partial index (that is, an index with a WHERE clause; so, "WHERE json_field LIKE '%foo.bar = baz%'" or whatever).
- jerrysievert 14y agoyou can, but in order to build a partial index, the function needs to be immutable. not exactly ideal in this case.
- rosser 14y agoImmutability is perfectly appropriate for that use-case, though. Creating an index via a function that may return different outputs when provided the same input is always going to lose.
- rhizome 14y agoIsn't this a category error? If you need to query within serialized data, you don't want to serialize. Normalize your database for this.
- rdtsc 14y agoOr de-normalize and keep your data serialized but also keep an additional index of data you want to query.
- rhizome 14y agoSerialized is already denormalized, you're talking about a kind of double-denormalization where you introduce metadata as a guide for the serialized-data queries. Spaghetti.
- randomdata 14y agoWouldn't that kind of defeat the purpose of using a document database in the first place? Being able to throw unstructured data into the system, and then being able to query on that data once the space is better understood is where the document databases really shine. If you are able to start with rigid structure, you, in many cases, could have just used a relational database to begin with.
- rhizome 14y agoWouldn't that kind of defeat the purpose of using a document database in the first place? Yes. Use the right tool for the job.
- mgkimsal 14y agoDefining 'right', and being able to predict 'right' for future iterations/versions of an app's life is where that mantra seems to fall down. I'm not a huge nosql fan right now, given that I sometimes need document-style schemaless data storage, but I always (eventually) need adhoc reporting and relational querying capabilities on projects. With that (fore)knowledge, I may as well always choose a relational db.