add comment explaining the <= :low condition

dcSpark · Mar 12, 2024 · 9ece156 · 9ece156
1 parent 9906695
commit 9ece156
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Showing 2 changed files with 17 additions and 1 deletion.
diff --git a/webserver/server/app/models/pagination/slotBoundsPagination.queries.ts b/webserver/server/app/models/pagination/slotBoundsPagination.queries.ts
@@ -19,7 +19,7 @@ export interface ISlotBoundsPaginationQuery {
   result: ISlotBoundsPaginationResult;
 }
 
-const slotBoundsPaginationIR: any = {"usedParamSet":{"low":true,"high":true},"params":[{"name":"low","required":true,"transform":{"type":"scalar"},"locs":[{"a":155,"b":159}]},{"name":"high","required":true,"transform":{"type":"scalar"},"locs":[{"a":409,"b":414}]}],"statement":"WITH\n    low_block AS (\n        SELECT\n            \"Block\".id,\n            \"Block\".slot\n        FROM\n            \"Block\"\n        WHERE\n            slot <= :low! AND tx_count > 0\n        ORDER BY\n            \"Block\".id DESC\n        LIMIT\n            1\n    ),\n    high_block AS (\n        SELECT\n            \"Block\".id,\n            \"Block\".slot\n        FROM\n            \"Block\"\n        WHERE\n            slot <= :high! AND tx_count > 0\n        ORDER BY\n            \"Block\".id DESC\n        LIMIT 1\n    ),\n    min_hash AS (\n        (SELECT\n            COALESCE(MAX(\"Transaction\".id), -1) AS min_tx_id\n        FROM\n            \"Transaction\"\n            JOIN low_block ON \"Transaction\".block_id = low_block.id\n        GROUP BY\n            low_block.slot\n        LIMIT\n            1\n        )\n        UNION (SELECT min_tx_id FROM (values(-1)) s(min_tx_id))\n        ORDER BY min_tx_id DESC\n        LIMIT\n            1\n    ),\n    max_hash AS (\n        SELECT\n            COALESCE(MAX(\"Transaction\".id), -2) AS max_tx_id\n        FROM\n            \"Transaction\"\n            JOIN high_block ON \"Transaction\".block_id = high_block.id\n        GROUP BY\n            high_block.slot\n    )\nSELECT\n    *\nFROM min_hash\nLEFT JOIN max_hash ON 1 = 1"};
+const slotBoundsPaginationIR: any = {"usedParamSet":{"low":true,"high":true},"params":[{"name":"low","required":true,"transform":{"type":"scalar"},"locs":[{"a":782,"b":786}]},{"name":"high","required":true,"transform":{"type":"scalar"},"locs":[{"a":1036,"b":1041}]}],"statement":"WITH\n    low_block AS (\n        SELECT\n            \"Block\".id,\n            \"Block\".slot\n        FROM\n            \"Block\"\n        WHERE\n                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  \n            slot <= :low! AND tx_count > 0\n        ORDER BY\n            \"Block\".id DESC\n        LIMIT\n            1\n    ),\n    high_block AS (\n        SELECT\n            \"Block\".id,\n            \"Block\".slot\n        FROM\n            \"Block\"\n        WHERE\n            slot <= :high! AND tx_count > 0\n        ORDER BY\n            \"Block\".id DESC\n        LIMIT 1\n    ),\n    min_hash AS (\n        (SELECT\n            COALESCE(MAX(\"Transaction\".id), -1) AS min_tx_id\n        FROM\n            \"Transaction\"\n            JOIN low_block ON \"Transaction\".block_id = low_block.id\n        GROUP BY\n            low_block.slot\n        LIMIT\n            1\n        )\n        UNION (SELECT min_tx_id FROM (values(-1)) s(min_tx_id))\n        ORDER BY min_tx_id DESC\n        LIMIT\n            1\n    ),\n    max_hash AS (\n        SELECT\n            COALESCE(MAX(\"Transaction\".id), -2) AS max_tx_id\n        FROM\n            \"Transaction\"\n            JOIN high_block ON \"Transaction\".block_id = high_block.id\n        GROUP BY\n            high_block.slot\n    )\nSELECT\n    *\nFROM min_hash\nLEFT JOIN max_hash ON 1 = 1"};
 
 /**
  * Query generated from SQL:
@@ -32,6 +32,7 @@ const slotBoundsPaginationIR: any = {"usedParamSet":{"low":true,"high":true},"pa
  *         FROM
  *             "Block"
  *         WHERE
+ *                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
  *             slot <= :low! AND tx_count > 0
  *         ORDER BY
  *             "Block".id DESC

diff --git a/webserver/server/app/models/pagination/slotBoundsPagination.sql b/webserver/server/app/models/pagination/slotBoundsPagination.sql
@@ -7,6 +7,21 @@ WITH
         FROM
             "Block"
         WHERE
+        /*
+            We use <= here even though slot filter parameter is exclusive on the
+            lower bound. This is because the tx that we find here (after joining
+            with min_hash) is used later in a condition of the form:
+
+            "Transaction".id > :after_tx_id!
+
+            For example.
+
+            Lets say :low is 1, and there is a block with txs at this slot. This
+            means we want to find _at least_ the first tx in slot 2.
+
+            So what we want in this query is to find the last tx in slot 1.
+            Then, when we use the > comparator we would get the right tx.
+        */
             slot <= :low! AND tx_count > 0
         ORDER BY
             "Block".id DESC