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Limitations
on Oracle SQL processing?
Oracle Tips by Burleson Consulting |
Question: I'm doing a
"group by rollup" and I'm concerned that there may be limitations to
the amount of processing that you can do within a SQL statement.
Answer:
Oracle will always return an error message when SQL fails.
David Aldridge notes a limitation on GROUP BY when using materialized views
that might apply.
"Oracle ’s attempt to index all the columns
of an aggregating materialized view fails when more than 32 columns are
included in the GROUP BY, and the error “ORA-01793: maximum number of index
columns is 32″ is raised."
Mark Rittman notes a problem with invoking automatic query rewrite for
materialized views when using GROUP BY ROLLUP:
"The problem is, that the query
rewrite mechanism won’t be able to make the connection between the GROUP BY
/ GROUP BY … ROLLUP used to request the summary on the relational data, and
the SQL used to expose the analytic workspace data through the OLAP_TABLE
function. It’ll never qualify for query rewrite"
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