DECNUMBERCALC FOR REDIS

Module that will allow you to make decimal calculations with redis. DecNumber library used - http://download.icu-project.org/files/decNumber/decNumber-icu-368.zip

1. Decimal number calculation module

A minimal module (module.o) implementing a few commands.

For now it includes 6 commands:

• DECIMAL.ADD - adds two numbers together.
• DECIMAL.SUBTRACT - subtract second number from the first one.
• DECIMAL.MULTIPLY - multiply two numbers.
• DECIMAL.QUANTIZE - quantizing number with given exponent and rounding mode.
• DECIMAL.DIVIDE - divide first number by second.
• DECIMAL.POWER - raise a first number to a power of second number.

Possible rounding modes:

ROUNDING MODE	How it works
ROUND_CEILING	round towards +infinity
ROUND_UP	round away from 0
ROUND_HALF_UP	0.5 rounds up
ROUND_HALF_EVEN	0.5 rounds to nearest even
ROUND_HALF_DOWN	0.5 rounds down
ROUND_DOWN	round towards 0 (truncate)
ROUND_FLOOR	round towards -infinity
ROUND_05UP	round for reround

All comand parameters given in strings.

Quick Start Guide

Here's what you need to do to build a module:

1. Run make in '/src' directory.

Run this module inside your redis instance: 2. Run redis loading the module: /path/to/redis-server --loadmodule ./module.so

Now run redis-cli and try the commands:

127.0.0.1:9979> DECIMAL.ADD 0.1337 0.1337
"0.2674"
127.0.0.1:9979> DECIMAL.SUBTRACT 0.1337 0.1337
"0"
127.0.0.1:9979> DECIMAL.MULTIPLY 2 0.1337
"0.2674"
127.0.0.1:9979> DECIMAL.QUANTIZE 0.1337 0.01 ROUND_UP
"0.14"
127.0.0.1:6379> DECIMAL.QUANTIZE 0.1337 0.01 ROUND_DOWN
"0.13"
127.0.0.1:6379> DECIMAL.POWER 10 -8
"1E-8"
127.0.0.1:6379> DECIMAL.POWER 10 -3
"0.001"
127.0.0.1:6379> DECIMAL.POWER 10 -3.3
"0.0005011872336272722850015541868849458"
127.0.0.1:6379> DECIMAL.POWER 1.337 8.08
"10.45061312363680871642582659256680"
127.0.0.1:6379> DECIMAL.DIVIDE 10 23
"0.4347826086956521739130434782608696"

or use inside lua script:

redis.call("DECIMAL.ADD", "0.1337", "0.1337")

Usage with redis cluster

Each command has a "cluster version"

• DECIMAL.ADD --> DECIMAL.ADD.C
• DECIMAL.SUBTRACT --> DECIMAL.SUBTRACT.C
• DECIMAL.MULTIPLY --> DECIMAL.MULTIPLY.C
• DECIMAL.QUANTIZE --> DECIMAL.QUANTIZE.C
• DECIMAL.DIVIDE --> DECIMAL.DIVIDE.C
• DECIMAL.POWER --> DECIMAL.POWER.C

IMPORTANT

Also, input parameter for cluster commands a slightly different -- first parameter is always a KEY, redis cluster will route command execution based on which slot this key belongs, next parameters are the same as for non-cluster commands. So, all cluster commands have by one parameter more than non-cluster commands. Cluster commands can be safely used in standalone redis setup, first parameter can be any key from your database, it will be ignored as command can only be executed on that server.

Use inside lua script:

redis.call("DECIMAL.ADD.C", "Foo", "0.1337", "0.1337")

Build using https://github.com/RedisLabs/RedisModulesSDK

Enjoy!