Improve handling of numeric-valued variables in pgbench.
The previous coding always stored variable values as strings, doing
conversion on-the-fly when a numeric value was needed or a number was to be
assigned. This was a bit inefficient and risked loss of precision for
floating-point values. The precision aspect had been hacked around by
printing doubles in "%.18e" format, which is ugly and has machine-dependent
results. Instead, arrange to preserve an assigned numeric value in the
original binary numeric format, converting to string only when and if
needed. When we do need to convert a double to string, convert in "%g"
format with DBL_DIG precision, which is the standard way to do it and
produces the least surprising results in most cases.
The implementation supports storing both a string value and a numeric
value for any one variable, with lazy conversion between them. I also
arranged for lazy re-sorting of the variable array when new variables are
added. That was mainly to allow a clean refactoring of putVariable()
into two levels of subroutine, but it may allow us to save a few sorts.
Discussion: <9188.1462475559@sss.pgh.pa.us>
Branch
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master
Details
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http://git.postgresql.org/pg/commitdiff/9515299485a591b3a8f03c118d11809d01663665
Modified Files
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src/bin/pgbench/pgbench.c | 274 +++++++++++++++++++++++++++++++---------------
1 file changed, 188 insertions(+), 86 deletions(-)