Questions about horizontal partitioning

Suppose I have a table - lets say it was developed by someone with little or no understanding of database design - and it has 230 columns.

Now, it turns out that 99% of the time only about 8 colums are required, but all 230 columns are populated. However, legacy applications (which are run nightly for batch processing, but not during the day, when heavy volume occurs) require the old table design. New applications only select a limited number of columns, but require the old design names.

I want to do the following:

1. Split the table into two tables (one with 6 columns, the other with 224 columns), using the primary key to establish a 1-1 relationship between them.
2. Create a view that displays the join between the two tables.

By doing this, I'm hoping that the query optimizer is smart enough to see that if a query comes in and requests only the six columns (that are in the narrower table) that PostgreSQL won't have to load the wider table into the buffer pool, and thereby actually have to only access about 10% the amount of disk that it presently does.

Is this a sound theory? Is the query optimizer smart enough ignore part of a join when a portion of the join will have no effect on the end result set?

thanks

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