[#231] fix broken endpoints

fix endpoints broken due to assumption that predefined dreps always exist, even if noone delegated to them

govtool/backend/sql/get-network-metrics.sql

@@ -21,17 +21,17 @@ with current_epoch as (
     select count(*) as count
     from drep_hash
 ), always_abstain_voting_power as (
-    select amount
-    from drep_distr
-    join drep_hash
+    select coalesce(amount, 0) as amount
+    from drep_hash
+    left join drep_distr
     on drep_hash.id = drep_distr.hash_id
     where drep_hash.view = 'drep_always_abstain'
     order by epoch_no desc
     limit 1
 ), always_no_confidence_voting_power as (
-    select amount
-    from drep_distr
-    join drep_hash
+    select coalesce(amount, 0) as amount
+    from drep_hash
+    left join drep_distr
     on drep_hash.id = drep_distr.hash_id
     where drep_hash.view = 'drep_always_no_confidence'
     order by epoch_no desc

govtool/backend/sql/get-voting-power.sql

@@ -1,5 +1,7 @@
-select drep_distr.amount
-from drep_distr
-join drep_hash
+select coalesce(drep_distr.amount, 0) as amount
+from drep_hash
+left join drep_distr
 on drep_hash.id = drep_distr.hash_id
-where drep_hash.raw = decode(?,'hex')
+where drep_hash.raw = decode(?,'hex')
+order by epoch_no desc
+limit 1

govtool/backend/sql/list-proposals.sql

@@ -10,17 +10,17 @@ WITH LatestDrepDistr AS (
         Max(end_time) as last_epoch_end_time
     FROM epoch
 ), always_no_confidence_voting_power as (
-    select amount
-    from drep_distr
-    join drep_hash
+    select coalesce(amount, 0) as amount
+    from drep_hash
+    left join drep_distr
     on drep_hash.id = drep_distr.hash_id
     where drep_hash.view = 'drep_always_no_confidence'
     order by epoch_no desc
     limit 1
 ), always_abstain_voting_power as (
-    select amount
-    from drep_distr
-    join drep_hash
+    select coalesce(amount, 0) as amount
+    from drep_hash
+    left join drep_distr
     on drep_hash.id = drep_distr.hash_id
     where drep_hash.view = 'drep_always_abstain'
     order by epoch_no desc

govtool/backend/src/VVA/DRep.hs

@@ -47,11 +47,9 @@ getVotingPower ::
   Text ->
   m Integer
 getVotingPower drepId = withPool $ \conn -> do
-  votingPower <-
-    sum . map (\(SQL.Only x) -> x) <$>
-        liftIO
-          (SQL.query @_ @(SQL.Only Scientific) conn getVotingPowerSql $
-            SQL.Only drepId)
+  [SQL.Only votingPower] <-
+    liftIO
+      (SQL.query @_ @(SQL.Only Scientific) conn getVotingPowerSql $ SQL.Only drepId)
   return $ floor votingPower
 
 listDRepsSql :: SQL.Query