Re: Money casting too liberal? - Mailing list pgsql-general
| From | Gavin Flower |
|---|---|
| Subject | Re: Money casting too liberal? |
| Date | |
| Msg-id | 515A8DB2.1060002@archidevsys.co.nz Whole thread Raw |
| In response to | Re: Money casting too liberal? (Gavan Schneider <pg-gts@snkmail.com>) |
| Responses |
Re: Money casting too liberal?
|
| List | pgsql-general |
On 30/03/13 04:08, Gavan Schneider wrote:
Some thoughts.I agree 100%.
The current MONEY type might be considered akin to ASCII. Perfect for a base US centric accounting system where there are cents and dollars and no need to carry smaller fractions. As discussed, there are some details that could be refined.
When it comes to this type being used in full blown money systems it lacks the ability to carry fractions of cents and keep track of currencies. It also needs to play nicer with other exact types such as numeric, i.e., no intermediate calculations as real.
Therefore the discussion is really about the desired role for the MONEY type. Should it be refined in its current dallar and cents mode? or, be promoted to a more universal role (akin to a shift from ASCII to UTF)?
If there is merit in making MONEY work for most situations involving financial transactions I think the following might apply:
- keep integer as the underlying base type (for performance)
- generalise the decimal multiplier of a MONRY column so a specific MONEY column can be what its creator wants (from partial cents to millions of dollars/Yen/Other, along with rounding/truncating rules as required by r the user of his/her external agencies)
- define the currency for a given column and only allow this to change in defined ways, and specifically forbid implicit changes such as would arise from altering LOCALE information
- ensure the MONEY type plays nice with other exact precision types, i.e., convert to REAL/FLOAT as a very last resort
Personally I don't think it is appropriate for the MONEY type to have variable characteristics (such as different currencies) within a given column, rather the column variable should define the currency along with the desired decimal-multiplier and whatever else is required. The actual values within the column remain as simple integers. This is mostly based on performance issues. If the MONRY type is to be used it has to offer real performance benefits over bespoke NUMERIC applications.
Regards
Gavan Schneider
In the bad old days when I was a COBOL programmer we always stored money in the COBOL equivalent of an integer (numeric without a fractional part) to avoid round off, but we displayed with a decimal point to digits to the left. So storing as an integer (actually bigint would be required) is a good idea, with parameters to say how many effective digits in the fractional part, and how many fractional digits to display etc. - as you said.
Cheers,
Gavin
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