Anyway, the load process at this customer had multiple steps. Truncate and then fill staging tables with the current data from various source systems. Use the data in those staging tables to update the first of the data vault tables. And then use a join between the same staging table plus the just updated data vault table, with a filter on the current date, to update all other data vault tables.
With some of the tables having more than 500 million rows and over 50 columns, this process needed some time. But that was not a problem. The load finished before the offices reopened. Usually. But not always. Sometimes, it would run a few hours longer. And nobody knew why the load would take extra time at those seemingly random moments.
Read on for the full story. It’s a sobering reminder that each environment is different, and something that worked really well in one environment may fare poorly elsewhere.
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