chore: Postgres enhance get oldest timestamp (#2687)

* postgres: consider also the existing paritions when getting oldest timestamp
* test_driver_postgres_query: adapt test to oldest timestamp

tests/waku_archive/test_driver_postgres_query.nim

@@ -1,7 +1,10 @@
 {.used.}
 
 import
-  std/[options, sequtils, random, algorithm], testutils/unittests, chronos, chronicles
+  std/[options, sequtils, strformat, random, algorithm],
+  testutils/unittests,
+  chronos,
+  chronicles
 import
   ../../../waku/waku_archive,
   ../../../waku/waku_archive/driver as driver_module,
@@ -1767,9 +1770,21 @@ suite "Postgres driver - queries":
         )
       ).isOk()
 
+    ## just keep the second resolution.
+    ## Notice that the oldest timestamps considers the minimum partition timestamp, which
+    ## is expressed in seconds.
+    let oldestPartitionTimestamp =
+      Timestamp(float(oldestTime) / 1_000_000_000) * 1_000_000_000
+
     var res = await driver.getOldestMessageTimestamp()
     assert res.isOk(), res.error
-    assert res.get() == oldestTime, "Failed to retrieve the latest timestamp"
+
+    ## We give certain margin of error. The oldest timestamp is obtained from
+    ## the oldest partition timestamp and there might be at most one second of difference
+    ## between the time created in the test and the oldest-partition-timestamp created within
+    ## the driver logic.
+    assert abs(res.get() - oldestPartitionTimestamp) < (2 * 1_000_000_000),
+      fmt"Failed to retrieve the latest timestamp {res.get()} != {oldestPartitionTimestamp}"
 
     res = await driver.getNewestMessageTimestamp()
     assert res.isOk(), res.error

waku/waku_archive/driver/postgres_driver/partitions_manager.nim

@@ -83,6 +83,9 @@ proc getLastMoment*(partition: Partition): int64 =
   let lastTimeInSec = partition.timeRange.`end`
   return lastTimeInSec
 
+proc getPartitionStartTimeInNanosec*(partition: Partition): int64 =
+  return partition.timeRange.beginning * 1_000_000_000
+
 proc containsMoment*(partition: Partition, time: int64): bool =
   ## Returns true if the given moment is contained within the partition window,
   ## 'false' otherwise.

waku/waku_archive/driver/postgres_driver/postgres_driver.nim

@@ -701,7 +701,10 @@ proc getInt(
   try:
     retInt = parseInt(str)
   except ValueError:
-    return err("exception in getInt, parseInt: " & getCurrentExceptionMsg())
+    return err(
+      "exception in getInt, parseInt, str: " & str & " query: " & query & " exception: " &
+        getCurrentExceptionMsg()
+    )
 
   return ok(retInt)
 
@@ -726,11 +729,20 @@ method getMessagesCount*(
 method getOldestMessageTimestamp*(
     s: PostgresDriver
 ): Future[ArchiveDriverResult[Timestamp]] {.async.} =
+  ## In some cases it could happen that we have
+  ## empty partitions which are older than the current stored rows.
+  ## In those cases we want to consider those older partitions as the oldest considered timestamp.
+  let oldestPartition = s.partitionMngr.getOldestPartition().valueOr:
+    return err("could not get oldest partition: " & $error)
+
+  let oldestPartitionTimeNanoSec = oldestPartition.getPartitionStartTimeInNanosec()
+
   let intRes = await s.getInt("SELECT MIN(storedAt) FROM messages")
   if intRes.isErr():
-    return err("error in getOldestMessageTimestamp: " & intRes.error)
+    ## Just return the oldest partition time considering the partitions set
+    return ok(Timestamp(oldestPartitionTimeNanoSec))
 
-  return ok(Timestamp(intRes.get()))
+  return ok(Timestamp(min(intRes.get(), oldestPartitionTimeNanoSec)))
 
 method getNewestMessageTimestamp*(
     s: PostgresDriver