(fix) Hotfix for duplicated entries for pools for epoch 568 on mainnet in pool_stat table

Author: Ciabas

govtool/backend/sql/list-proposals.sql

@@ -113,15 +113,28 @@ RankedPoolVotes AS (
         vp.vote
     FROM
         voting_procedure vp
-    WHERE 
+    WHERE
         vp.pool_voter IS NOT NULL
         AND vp.gov_action_proposal_id IN (SELECT id FROM ActiveProposals)
-    ORDER BY 
-        vp.pool_voter, 
-        vp.gov_action_proposal_id, 
+    ORDER BY
+        vp.pool_voter,
+        vp.gov_action_proposal_id,
         vp.tx_id DESC,
         vp.id DESC
 ),
+-- This CTE retrieves the latest pool statistics for each pool in the current epoch.
+-- It ensures that we only consider the most recent data for each pool.
+-- it's a hotfix for duplication issue https://github.com/IntersectMBO/cardano-db-sync/issues/1986
+LatestPoolStat AS (
+    SELECT DISTINCT ON (pool_hash_id, epoch_no, number_of_blocks, number_of_delegators, stake, voting_power)
+        *
+    FROM
+        pool_stat
+    WHERE
+        epoch_no = (SELECT MAX(no) FROM epoch)
+    ORDER BY
+        pool_hash_id, epoch_no, number_of_blocks, number_of_delegators, stake, voting_power, id DESC
+),
 PoolVotes AS (
     SELECT
         rpv.gov_action_proposal_id,
@@ -132,10 +145,10 @@ PoolVotes AS (
         SUM(CASE WHEN rpv.vote = 'Yes' THEN ps.voting_power ELSE 0 END) AS poolYesVotes,
         SUM(CASE WHEN rpv.vote = 'No' THEN ps.voting_power ELSE 0 END) AS poolNoVotes,
         SUM(CASE WHEN rpv.vote = 'Abstain' THEN ps.voting_power ELSE 0 END) AS poolAbstainVotes
-    FROM 
+    FROM
         RankedPoolVotes rpv
-    JOIN 
-        pool_stat ps
+    JOIN
+        LatestPoolStat ps
         ON rpv.pool_voter = ps.pool_hash_id
     WHERE
         ps.epoch_no = (SELECT MAX(no) FROM epoch)