Category: Programming

Missing indexes in Oracle

Some little details cause trouble entirely disproportionate to their importance. One such thing is a little quirk in how Oracle handles indexes. I have some code which gets a list of tables using a particular criteria and then...

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Parsing doubles in Finland

One problem I had this week is that a piece of code which had, for the previous few years, been perfectly behaved suddenly started crashing for a new customer. This was the first time I’d seen the code run on a Finnish...

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Oracle, index-organized tables, and overflow tablespaces

SQL Error: ORA-25191: cannot reference overflow table of an index-organized table

A refresher: a SQL database is relational, and rows are stored unsorted; Oracle calls standard tables heap-organized tables. For a given SQL query, unless an ORDER BY clause is used, results can be returned in any order. Oracle also has IOTs, which are tables that are instead stored in a B*Tree index structure. This structure stores all columns of the table, sorted by primary key; because this is both the table and the index, accessing rows is much faster and less storage space is needed than for a heap-organized table with a separate index.

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