Android Room在运行时确定查询中的列名称

Question

This is my Value table structure

varName   value    timestamp    oneHour    oneDay    oneWeek
============================================================
varA      12.7     129387230    true       false     false
varB      32.0     129387230    true       true      false
varA      32.2     129387234    true       true      true
...

As you can see, each entry has one or more flags that determine whether this entry is used in a graph with the corresponding timescale.

In my Dao I have a query to get all values of a timescale for a variable. Timescale is just an enum with oneHour, oneDay, oneWeek

@Query("SELECT * FROM Value WHERE varName = :varName AND [       ] ORDER BY timestamp ASC")
fun getByTimescale(varName: String, timescale: Timescale): Flowable<List<Value>>

In the bracket, I want to do something like timescale.name = true , but that would throw an error.

Answer 1

Changing the query at runtime would not be possible as Room generates code during build time based on the SQL query to fetch the result. Changing query means changing the method implementation.

You can achieve this by creating 3 queries, one for each enum value. Then at runtime, decide which of the 3 methods you need to call.