List available cohort definitions

Queries each connected server for existing cohort definitions. Returns a named list (one entry per server) of data frames describing the cohorts that are usable for analysis. This is useful for discovering cohorts that have already been created in persistent storage.

Usage

ds.omop.cohort.list(symbol = "omop", conns = NULL)

Arguments

symbol

Character; the session symbol used when the OMOP connection was initialised (default: "omop").

conns

DSI connection object(s). If NULL (the default), the connections stored in the active session are used.

Value

Named list (one entry per server) of data frames with cohort metadata. Each row is a cohort at or above the server's nfilter_subset threshold; its reported size is BANDED to a multiple of nfilter_band (never the exact subject count). Sub-threshold cohorts are intentionally absent. Returns an empty list (or per-server empty data frames) when no cohort clears the threshold.

Disclosure control

Listing is gated server-side and is intentionally a partial, approximate view so that discovery is itself disclosure-safe:

• Only cohorts whose distinct-subject count reaches the server's per-subset threshold (nfilter_subset) appear. A cohort below that threshold is OMITTED entirely – it never shows up in the listing, exactly as if it did not exist. You therefore cannot use the listing to learn that a small cohort exists.

• Each surviving cohort's size is BANDED (rounded down to a multiple of nfilter_band), never the exact subject count, so the listing cannot be differenced to recover an individual's membership.

The net effect: you can discover the cohorts you can actually use and their approximate size, but never tiny cohorts and never an exact count. The gating and banding happen on the server through the shared disclosure helpers; the client surfaces the server's response unchanged.

Examples

if (FALSE) { # \dontrun{
cohorts <- ds.omop.cohort.list()
cohorts[["server_a"]]
} # }