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118 lines
4.6 KiB
Markdown
118 lines
4.6 KiB
Markdown
---
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title: when two macros are faster than one
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draft: "false"
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---
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While working on my Database datapack (still WIP), I knew I'd want to find
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# scenario
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## dataset
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The data is stored in a storage `#_macro.array`. Array is populated with a total of 500 entries, each having `id` and `string` fields.
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```json
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[
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{
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id: 1,
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string: "entry1"
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},
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...
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{
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id: 500,
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string: "entry500"
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}
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]
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```
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## constraints
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The objective is to create an interface that receives a keyword, say `entry500`, and searches `#_macro.array` for an entry where the value of `string` matches the keyword.
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The keyword must be able to be entered by a player at runtime, and `#_macro.array` can have an arbitrary number of custom entries created by a player.
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In TypeScript, it would look something like this:
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```ts
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function searchArray(keyword: string) {
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// logic
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return theRelevantEntry
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}
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searchArray('entry500')
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```
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In mcfunction, this is not so straightforward. Macros would make this really clean:
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```vb
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function test_namespace:search_array {keyword: "entry500"}
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```
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Unfortunately, macros come with a performance hit. A more performant method, albeit less elegant, is to store the keyword in NBT storage prior to calling the function. The storage can be removed after the function is run:
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```vb
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data modify storage test_namespace:test_namespace temp.keyword set value 'entry500'
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function test_namespace:search_array
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data remove storage test_namespace:test_namespace temp.keyword
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```
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Once the entry is found, it is stored in the `temp.result` storage, which can then be consumed by another function.
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Now for the logic to do the actual array searching...
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# one macro
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Macros allow us to reach into our array and pick out an entry that matching value in the `string` property. This is something that I didn't realize (for some reason) and was pointed out by **PuckiSilver** and **amandin** on the Datapack Hub discord server.
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```vb
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... one_macro.array[string:$(keyword)]
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```
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This method is super clean and results in a one liner that is wordy but simple:
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```vb
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'# one_macro/_searcharray.mcfunction
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$data modify storage test_namespace:test_namespace temp.result set from storage test_namespace:test_namespace one_macro.array[string:$(keyword)]
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```
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`_searcharray` can then be called using the `temp.keyword` storage:
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```vb
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'# one_macro/run.mcfunction
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data modify storage test_namespace:test_namespace temp.keyword set value 'entry500'
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function test_namespace:one_macro/_searcharray with storage test_namespace:test_namespace temp
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data remove storage test_namespace:test_namespace temp.keyword
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'# call the function that consumes 'temp.result', then remove it
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data remove storage test_namespace:test_namespace temp.result
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```
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# two macro
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Another way to crack the problem is through indexing. This was my original plan when I didn't realize that `...[string:$(keyword)]` was possible.
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This method requires the creation of an index of the field that is going to be searched. The index will look something like this:
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```json
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[
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{entry1: 0},
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{entry2: 1},
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...
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{entry500: 499}
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]
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```
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The *key*, e.g. `entry2:` corresponds with the value of a `string` field in the main array, while the value `1` indicates the main array index where we'll find the full entry. The index can be searched with a direct path, `index.$(keyword)`, and the main array can also be searched with a direct reference to the entry index, `array.#(index)`. Keep in mind that *the index must already exist prior to running the search function*. In a practical application, an index could be updated every time the main array is updated. A scheduled task could also audit the index to ensure that it's up to date.
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The index search looks like this:
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```vb
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'# two_macro/_searchindex.mcfunction
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$data modify storage test_namespace:test_namespace temp.index set from storage test_namespace:test_namespace two_macro.index.$(keyword)
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```
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And the array search looks like this:
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```vb
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'# two_macro/_searcharray.mcfunction
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$data modify storage test_namespace:test_namespace temp.result set from storage test_namespace:test_namespace two_macro.array[$(index)]
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```
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The index and array search functions are then called using the `temp.keyword` storage:
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```vb
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'# two_macro/run.mcfunction
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data modify storage test_namespace:test_namespace temp.keyword set value 'entry500'
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function test_namespace:two_macro/_searchindex with storage test_namespace:test_namespace temp
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function test_namespace:two_macro/_searcharray with storage test_namespace:test_namespace temp
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data remove storage test_namespace:test_namespace temp.keyword
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data remove storage test_namespace:test_namespace temp.index
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'# call the function that consumes 'temp.result', then remove it
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data remove storage test_namespace:test_namespace temp.result
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```
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