tarantool / tarantool / 15205162899

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Build Type

push

github

Committed by sergepetrenko

Commit Message

box: introduce fixed point decimals

Part of tarantool/tarantool-ee#1188

@TarantoolBot document
Title: Introduce fixed point decimals

Added support for fixed point decimal types `decimal32`, `decimal64`,
`decimal128` and `decimal256`. They differ in number of significant
decimal digits:

- `decimal32`  - 9
- `decimal64`  - 18
- `decimal128` - 38
- `decimal256` - 76

These types also has additional parameter `scale` which defines the
position of decimal point or it can be seen as implied decimal exponent
with value of `-scale`. For example type `decimal32` with `scale = 4`
can represent values from `-99999.9999` to `99999.9999`. And decimal
with `scale = -2` can represent values from `-999999999 * 10^2` to
`999999999 * 10^2`.

Example 1. Creating space with field of fixed decimal type.
```lua
s = box.schema.create_space('test', {format = {
    {'a', 'unsigned'}, {'b', 'decimal32', scale = 4},
}})
```
Decimal values can be created using `decimal` module. It changed to
be able to represent values of new types:

- limitation on exponent is removed
- precision is increased to 76 decimal digits
- printing is done in scientific notation

Example 2. Passing decimal values.
```lua
local decimal = require('decimal')
s = box.schema.create_space('test', {format = {
    {'a', 'unsigned'}, {'b', 'decimal32', scale = 4},
}})
s:create_index('pk')
s:insert({1, decimal.new(13333)})
s:insert({2, decimal.new(0.0017)})
```

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