11283: Add explanatory comment to SQL query.

Arvados-DCO-1.1-Signed-off-by: Tom Clegg <tom@curoverse.com>

diff --git a/services/api/app/models/node.rb b/services/api/app/models/node.rb
index e1c1e649143c3f142acb24c7e9525c5247d4800d..8eb40f9fbb7d9e96988a233b1436f491ef665cff 100644 (file)
--- a/services/api/app/models/node.rb
+++ b/services/api/app/models/node.rb
@@ -139,6 +139,9 @@ class Node < ArvadosModel
   protected
 
   def self.available_slot_number
+    # Join the sequence 1..max with the nodes table. Return the first
+    # (i.e., smallest) value that doesn't match the slot_number of any
+    # existing node.
     connection.exec_query('SELECT n FROM generate_series(1, $1) AS slot(n)
                           LEFT JOIN nodes ON n=slot_number
                           WHERE slot_number IS NULL