OT: postgres 8.1 features ... possible pressure on migration of features from enterprise edition down to standard edition?

  • From: Paul Drake <bdbafh@xxxxxxxxx>
  • To: oracle list <oracle-l@xxxxxxxxxxxxx>
  • Date: Tue, 8 Nov 2005 16:20:10 -0500


The following seemed interesting to me.

block quote:

Allow index scans to use an intermediate in-memory bitmap (Tom)

In previous releases, only a single index could be used to do lookups
on a table. With this feature, if a query has WHERE tab.col1 = 4 and
tab.col2 = 9, and there is no multicolumn index on col1 and col2, but
there is an index on col1 and another on col2, it is possible to
search both indexes and combine the results in memory, then do heap
fetches for only the rows matching both the col1 and col2
restrictions. This is very useful in environments that have a lot of
unstructured queries where it is impossible to create indexes that
match all possible access conditions. Bitmap scans are useful even
with a single index, as they reduce the amount of random access
needed; a bitmap index scan is efficient for retrieving fairly large
fractions of the complete table, whereas plain index scans are not.

"Allow nonconsecutive index columns to be used in a multicolumn index (Tom)

For example, this allows an index on columns a,b,c to be used in a
query with WHERE a = 4 and c = 10. "

"Allow TRUNCATE to truncate multiple tables in a single command (Alvaro)

Because of referential integrity checks, it is not allowed to truncate
a table that is part of a referential integrity constraint. Using this
new functionality, TRUNCATE can be used to truncate such tables, if
both tables involved in a referential integrity constraint are
truncated in a single TRUNCATE command. "

On a more humorous note, here is one feature that I'm glad Oracle does
not support:

 "Make REINDEX DATABASE reindex all indexes in the database ".


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