Cloud Spanner DB - Unable to read timestamp from ReadOnlyTransaction.getReadTimestamp() - google-cloud-platform

Question

I was trying to use ReadOnlyTransaction.getReadTimestamp() function but I keep running into exception:
"Method can only be called after read has returned data or finished"
I have returned one or two records from DB, but I can't read timestamp.
Below is sample code how and what I am doing.
IO {
val db = spannerClientInstance
val rotxn = db.singleUseReadOnlyTransaction()
val sql = "SELECT " +
"Name " +
"FROM Person " +
"WHERE Name= #Name"
val resultSet = db.singleUse.executeQuery(
Statement.newBuilder(sql).bind("Name").to(name).build()
)
(resultSet, rotxn)
}.bracket {
case (resultSet, rotxn) =>
IO {
val result =
scala.collection.mutable.Map.empty[String, Person]
while (resultSet.next()) {
result += (resultSet.getString(0) -> new Person(resultSet.getString(0)))
}
(result.toMap, rotxn.getReadTimestamp)
}
} {
case (resultSet, _) =>
IO(resultSet.close())
}
I tried closing resultSet and/or rotxn with resultSet.close() and rotxn.close() and then calling rotxn.getReadTimestamp(), but didn't have much luck. I got the same error message.
I am using Spanner Java lib: com.google.cloud:google-cloud-spanner:2.0.1
Tried googling the issue but didn't find much. Any help is welcomed :)
Thanks. :)

Answer 1

It seems that you are not actually executing the query on the read-only transaction that you started. The code that is executing the query is:
val resultSet = db.singleUse.executeQuery(
Statement.newBuilder(sql).bind("Name").to(name).build()
)
That query is using a single-use read-only transaction, and not your previously read-only transaction. Try executing it like this instead:
val resultSet = rotxn.executeQuery(
Statement.newBuilder(sql).bind("Name").to(name).build()
)