Move most /contrib README files into SGML. Some still need conversion

or will never be converted.

1 files changed, 0 insertions, 55 deletions

diff --git a/contrib/intagg/README.int_aggregate b/contrib/intagg/README.int_aggregate
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-Integer aggregator/enumerator.
-
-Many database systems have the notion of a one to many table.
-
-A one to many table usually sits between two indexed tables, 
-as: 
-
-create table one_to_many(left int, right int) ;
-
-And it is used like this:
-
-SELECT right.* from right JOIN one_to_many ON (right.id = one_to_many.right) 
-	WHERE  one_to_many.left = item;
-
-This will return all the items in the right hand table for an entry 
-in the left hand table. This is a very common construct in SQL.
-
-Now, this methodology can be cumbersome with a very large number of
-entries in the one_to_many table. Depending on the order in which
-data was entered, a join like this could result in an index scan
-and a fetch for each right hand entry in the table for a particular
-left hand entry.
-
-If you have a very dynamic system, there is not much you can do. 
-However, if you have some data which is fairly static, you can
-create a summary table with the aggregator.
-
-CREATE TABLE summary as SELECT left, int_array_aggregate(right) 
-	AS right FROM one_to_many GROUP BY left;
-
-This will create a table with one row per left item, and an array
-of right items. Now this is pretty useless without some way of using
-the array, thats why there is an array enumerator.
-
-SELECT left, int_array_enum(right) FROM summary WHERE left = item;
-
-The above query using int_array_enum, produces the same results as:
-
-SELECT left, right FROM one_to_many WHERE left = item;
-
-The difference is that the query against the summary table has to get
-only one row from the table, where as the query against "one_to_many"
-must index scan and fetch a row for each entry.
-
-On our system, an EXPLAIN shows a query with a cost of 8488 gets reduced
-to a cost of 329. The query is a join between the one_to_many table,
-
-select right, count(right) from 
-(
-	select left, int_array_enum(right) as right from summary join
-                (select left from left_table where left = item) as lefts
-                 ON (summary.left = lefts.left ) 
-) as list group by right order by count desc ;
-
-