I could swear I sent an example of this kind to the list years ago, but
I couldn't find it quickly, so here's a new one! The function
[matching] is fine to call with expressions that are only determined at
runtime.
I do believe all of the ingredients (e.g. parser extensions) here are
documented in the manual, but admittedly it's not trivial to piece them
all together into a sufficient intuitive understanding.
table t : { A : int, B : int }
datatype int_exp =
A
| B
| Plus of int_exp * int_exp
datatype bool_exp =
Eq of int_exp * int_exp
| And of bool_exp * bool_exp
fun int_exp (e : int_exp) : sql_exp [T = [A = int, B = int]] [] [] int =
case e of
A => (SQL t.A)
| B => (SQL t.B)
| Plus (e1, e2) => (SQL {int_exp e1} + {int_exp e2})
fun bool_exp (e : bool_exp) : sql_exp [T = [A = int, B = int]] [] [] bool =
case e of
Eq (e1, e2) => (SQL {int_exp e1} = {int_exp e2})
| And (e1, e2) => (SQL {bool_exp e1} AND {bool_exp e2})
fun matching (e : bool_exp) : transaction (list {A : int, B : int}) =
queryL1 (SELECT * FROM t WHERE {bool_exp e})
On 06/02/2015 03:43 PM, Sergey Mironov wrote:
Hi! I am trying to implement a post-query filter. Of cause it is
possible to use [queryL] followed by server-side filtering code, but
using the DB engine is a better solution in my case.
Typically, I'd like to convert a list of string patterns to a WHERE
clause of the form (OR Field LIKE {[patter1]} OR Filed LIKE
{[pattern2]} OR ... pattern x ... OR FALSE)
I think it should be possible to write it in Ur/Web, but I can't
remember any examples demonstrating this. Is it really possible?
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