Import the subgraph reachable from root_id in src into dst.

Node ids are renumbered; a SourceNode identical in (path, band, nodata, grid, dtype) to one already in dst is deduplicated, and every node imported from src is memoised in dst, so importing the same foreign node again (or a descendant of an already-imported node) reuses the existing local copy instead of planting a second chain. Without this a lazy raster built on one graph and referenced from several consumers on another gained one full read+compute chain per consumer (hutan's fused SI tail: 4-6 predicts per year, 2026-09-03). Graphs are append-only (rewrites swap nodes in place, ids never reorder), so ascending id order within the reachable set is a valid topological order.

Usage

graph_import(dst, src, root_id)

Arguments

dst

Destination Graph (modified by reference).

src

Source Graph.

root_id

Id in src whose ancestry is imported.

Value

The id of the imported root in dst.

See also

Other graph functions: Graph(), graph_add(), graph_get(), graph_ids(), graph_new(), graph_replace(), graph_toposort()