pgr_dijkstra combinations SQL

[mahmsakr]

My program needs to compute the shortest path between millions of (source, target) combinations on the same edges_table. It is very inefficient to do millions of calls to pgr_dijkstra, each of which will construct the same graph from the edges_table.

An efficient way to do it is to add a new signature as follows:
pgr_dijkstra(
edges_sql,
combinations_sql, -- a table (possibly big) of with two attributes source, target
directed)
Like this, one call will constrcut the graph once, and compute as many shortest paths as returned by the combinations_sql.