Balance between table and database user defined function

[sharkAndshark]

Hi guys.Here some very naive thoughts.If it's not Ok,just ignore.

There are two implementations of source for PostgreSQL : table/view, database function.If user want something a little beyond table,like tile grid 4326,filtering by some condition,cross tables/schema query...Choices they have:

• Create a view if it can solve the problem
• Asking help from database function

Parametrized Custom sql source

Could we introduce another implementation of PostgreSQL source ,like:

custom_sql: ……. ST_TileEnvelope(@z, @x,@y) …. WHERE geom && ST_TileEnvelope(@z,@x,@y)….

And Martin will inject z,x,y (or even other custom parameters from front end query )to sql in runtime.

[nyurik]

I was thinking about it too - essentially the usecase is a read-only database (no matter how unlikely), and a SQL statement that is used to generate a tile. We can use the same approach I did in the tilelive-pgquery - where a user-supplied query is examined (by asking DB to parse it), and made into a data source. I'm all for prototyping it if you want. This probably should have been an issue rather than a discussion, but either one is ok.