>From contrib/pgbench/pgbench.c starting in revision 1.77

     * Note: TPC-B requires at least 100 bytes per row, and the "filler"
     * fields in these table declarations were intended to comply with that.
     * But because they default to NULLs, they don't actually take any
     * space.  We could fix that by giving them non-null default values.
     * However, that would completely break comparability of pgbench
     * results with prior versions.  Since pgbench has never pretended
     * to be fully TPC-B compliant anyway, we stick with the historical
     * behavior.

The statement about NULLs applies to the other 3 tables, but
pgbench_accounts.filler is loaded (via COPY) as empty strings, not as
NULLs.  When stored into char(84), the empty string takes the full
specified storage.  So on my system, rows in pgbench_accounts take up
about 130 bytes, rather than than the about 40 they would with a NULL.

The behavior probably won't be changed, but the code comment probably
should be.  Sorry if this seems like picayune thing, but it led to a
bit of head scratching until I figured it out.

Cheers,

Jeff

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