1.4 Query Catamorphisms

(query/foldl [#:connection con] proc init sql) → any/c

con : connection? = (current-connection)

proc : procedure?

init : any/c

sql : string?

Executes sql, left-folding proc over the resulting rows, using init as the initial seed. This call is semantically identical to:

(let ((result (query #:connection con sql)))

(if (result-set? result)

(foldl (λ (x xs) (apply proc (append x (list xs))))

init

(map vector->list (result-set-rows result)))

result))

... but is far more efficient in both time and space.

Note that the result of the query may be a side-effect, in which case no iteration occurs and the result is simply returned.

(query/map [#:connection con] proc sql?)

→ (or/c side-effect? list?)

con : connection? = (current-connection)

proc : procedure?

sql? : string?

Executes sql, mapping proc over the resulting rows. This call is semantically identical to:

(let ((result (query #:connection con sql)))

(if (result-set? result)

(map (λ (xs) (apply proc xs))

(map vector->list (result-set-rows result)))

result))

... but is far more efficient in time and space.

(query/map/filter  [ #:connection con]             proc             pred?             sql)   →   (or/c side-effect? list?)

con : connection? = (current-connection)

proc : procedure?

pred? : procedure?

sql : string?

Executes sql, mapping proc over the rows in the result set that satisfy pred?. This call is semantically identical to:

(let ((result (query #:connection con sql)))

(if (result-set? result)

(map (λ (xs) (apply proc xs))

(filter (λ (xs) (apply pred? xs))

(map vector->list (result-set-rows result))))

result))

... but is far more efficient in time and space.

(execute/foldl proc init stmt args) → any/c   proc : procedure?   init : any/c   stmt : prepared-statement?   args : list?

(execute/map proc stmt args) → (or/c side-effect list?)   proc : procedure?   stmt : prepared-statement?   args : list?

(execute/map/filter proc pred? stmt args)  → (or/c side-effect? list?)   proc : procedure?   pred? : procedure?   stmt : prepared-statement?   args : list?

These procedures behave exactly like their query/... counterparts, except they take prepared statements and argument lists, rather than SQL strings.