Batching “UPDATE vs. INSERT” Queries Against Oracle Database

Question

Let's assume that I have an Oracle database with a table called RUN_LOG I am using to record when jobs have been executed.

The table has a primary key JOB_NAME which uniquely identifies the job that has been executed, and a column called LAST_RUN_TIMESTAMP which reflects when the job was last executed.

When an job starts, I would like to update the existing row for a job (if it exists), or otherwise insert a new row into the table.

Given Oracle does not support a REPLACE INTO -style query, it is necessary to try an UPDATE , and if zero rows are affected follow this up with an INSERT .

This is typically achieved with jdbc using something like the following:

PreparedStatement updateStatement = connection.prepareStatement("UPDATE ...");
PreparedStatement insertStatement = connection.prepareStatement("INSERT ...");

updateStatement.setString(1, "JobName");
updateStatement.setTimestamp(2, timestamp);

// If there are no rows to update, it must be a new job...
if (updateStatement.executeUpdate() == 0) {
    // Follow-up 
    insertStatement.setString(1, "JobName");
    insertStatement.setTimestamp(2, timestamp);
    insertStatement.executeUpdate();
}

This is a fairly well-trodden path, and I am very comfortable with this approach.

---

However , let's assume my use-case requires me to insert a very large number of these records. Performing individual SQL queries against the database would be far too "chatty". Instead, I would like to start batching these INSERT / UPDATE queries

Given the execution of the UPDATE queries will be deferred until the batch is committed, I cannot observe how many rows are affected until a later date.

What is the best mechanism for achieving this REPLACE INTO -like result?

I'd rather avoid using a stored procedure, as I'd prefer to keep my persistence logic in this one place (class), rather than distributing it between the Java code and the database.

Answer 1

What about the SQL MERGE statement. You can insert large number of records to temporary table, then merge temp table with RUN_LOG For example:

merge into RUN_LOG tgt using (
   select job_name, timestamp 
   from my_new_temp_table 
) src 
on (src.job_name = tgt.job_name) 
when matched then update set
   tgt.timestamp = src.timestamp
when not matched then insert values (src.job_name, src.timestamp)
;