Separate SELECT Queries on All Status Tables |
Every time Iguana polls for a message from the database, it will execute a select query on each message that was defined in the vmd file. The select query will utilize the MIN() or MAX() function (for ascending or descending, respectively) to retrieve just one row from each table (no limits required).
When Iguana iterates through all the retrieved values, it will know which message has the global minimum/maximum MESSAGE_ID (or other order by column).
For example:
| MessageA | MESSAGE_ID | STATUS |
|---|---|---|
| 2 | W |
| MessageB | MESSAGE_ID | STATUS |
|---|---|---|
| 1 | W |
| MessageC | MESSAGE_ID | STATUS |
|---|---|---|
| 3 | W |
- SELECT MIN(MESSAGE_ID) FROM MESSAGEA; => GlobalMin = MessageA[2]
- SELECT MIN(MESSAGE_ID) FROM MESSAGEB; => GlobalMin = MessageB[1]
- SELECT MIN(MESSAGE_ID) FROM MESSAGEC; => GlobalMin still MessageB[1]
Therefore, Iguana sends MessageB[1]. After sending, Iguana re-executes the queries and sends MessageA[2].
Re-executing the queries will handle situations where you decide to rearrange the order of messages of, say, MessageA[2] and MessageC[3] before MessageB[1] is finished.
If all tables are empty, Iguana will wait for the poll time (as it does now) before re-executing the queries.