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nicer reduce example
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@ -12,16 +12,14 @@ e.g.
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On the LHS we are configuring the collection of items that will be reduced `<exp>` as well as what each element will be called `$<name>`. Note that the array has been splatted into its individual elements.
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On the LHS we are configuring the collection of items that will be reduced `<exp>` as well as what each element will be called `$<name>`. Note that the array has been splatted into its individual elements.
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On the RHS there is `<init>`, the starting value of the accumulator and `<block>`, the expression that will update the accumulator for each element in the collection.
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On the RHS there is `<init>`, the starting value of the accumulator and `<block>`, the expression that will update the accumulator for each element in the collection. Note that within the block expression, `.` will evaluate to the current value of the accumulator.
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Note that within the block expression, `.` will evaluate to the current value of the accumulator. This effectively means that within the `reduce` block you can no longer access data other than elements of the array set as `$<name>`. For simple things, this is probably fine, but often you will need to refer to other data elements.
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This can be done by setting a variable using `as` and piping that into the `reduce` operation, or you can simply refer to `$context` which is exactly that, automatically set for you for convenience. See examples below.
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## yq vs jq syntax
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## yq vs jq syntax
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Reduce syntax in `yq` is a little different from `jq` - as `yq` (currently) isn't as sophisticated as `jq` and its only supports infix notation (e.g. a + b, where the operator is in the middle of the two parameters) - where as `jq` uses a mix of infix notation with _prefix_ notation (e.g. `reduce a b` is like writing `+ a b`).
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Reduce syntax in `yq` is a little different from `jq` - as `yq` (currently) isn't as sophisticated as `jq` and its only supports infix notation (e.g. a + b, where the operator is in the middle of the two parameters) - where as `jq` uses a mix of infix notation with _prefix_ notation (e.g. `reduce a b` is like writing `+ a b`).
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To that end, the reduce operator is called `ireduce` for backwards compatability if a prefix version of `reduce` is ever added.
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To that end, the reduce operator is called `ireduce` for backwards compatability if a `jq` like prefix version of `reduce` is ever added.
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## Sum numbers
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## Sum numbers
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Given a sample.yml file of:
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Given a sample.yml file of:
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```yaml
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```yaml
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@ -39,6 +37,25 @@ will output
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20
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20
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```
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```
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## Merge all yaml files together
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Given a sample.yml file of:
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```yaml
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a: cat
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```
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And another sample another.yml file of:
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```yaml
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b: dog
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```
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then
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```bash
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yq eval-all '. as $item ireduce ({}; . * $item )' sample.yml another.yml
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```
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will output
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```yaml
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a: cat
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b: dog
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```
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## Convert an array to an object
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## Convert an array to an object
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Given a sample.yml file of:
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Given a sample.yml file of:
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```yaml
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```yaml
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@ -57,47 +74,3 @@ Cathy: apples
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Bob: bananas
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Bob: bananas
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```
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```
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## Merge all documents together - using context
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The _$context_ variable set by reduce lets you access the data outside the reduce block.
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Given a sample.yml file of:
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```yaml
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a: cat
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```
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And another sample another.yml file of:
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```yaml
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b: dog
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```
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then
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```bash
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yq eval-all 'fileIndex as $item ireduce ({}; . * ($context | select(fileIndex==$item)) )' sample.yml another.yml
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```
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will output
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```yaml
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a: cat
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b: dog
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```
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## Merge all documents together - without using context
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`$context` is just a convenient variable that `reduce` sets, you can use your own for more control
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Given a sample.yml file of:
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```yaml
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c:
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a: cat
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```
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And another sample another.yml file of:
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```yaml
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c:
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b: dog
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```
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then
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```bash
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yq eval-all '.c as $root | fileIndex as $item ireduce ({}; . * ($root | select(fileIndex==$item)) )' sample.yml another.yml
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```
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will output
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```yaml
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a: cat
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b: dog
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```
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@ -12,13 +12,10 @@ e.g.
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On the LHS we are configuring the collection of items that will be reduced `<exp>` as well as what each element will be called `$<name>`. Note that the array has been splatted into its individual elements.
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On the LHS we are configuring the collection of items that will be reduced `<exp>` as well as what each element will be called `$<name>`. Note that the array has been splatted into its individual elements.
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On the RHS there is `<init>`, the starting value of the accumulator and `<block>`, the expression that will update the accumulator for each element in the collection.
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On the RHS there is `<init>`, the starting value of the accumulator and `<block>`, the expression that will update the accumulator for each element in the collection. Note that within the block expression, `.` will evaluate to the current value of the accumulator.
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Note that within the block expression, `.` will evaluate to the current value of the accumulator. This effectively means that within the `reduce` block you can no longer access data other than elements of the array set as `$<name>`. For simple things, this is probably fine, but often you will need to refer to other data elements.
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This can be done by setting a variable using `as` and piping that into the `reduce` operation, or you can simply refer to `$context` which is exactly that, automatically set for you for convenience. See examples below.
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## yq vs jq syntax
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## yq vs jq syntax
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Reduce syntax in `yq` is a little different from `jq` - as `yq` (currently) isn't as sophisticated as `jq` and its only supports infix notation (e.g. a + b, where the operator is in the middle of the two parameters) - where as `jq` uses a mix of infix notation with _prefix_ notation (e.g. `reduce a b` is like writing `+ a b`).
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Reduce syntax in `yq` is a little different from `jq` - as `yq` (currently) isn't as sophisticated as `jq` and its only supports infix notation (e.g. a + b, where the operator is in the middle of the two parameters) - where as `jq` uses a mix of infix notation with _prefix_ notation (e.g. `reduce a b` is like writing `+ a b`).
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To that end, the reduce operator is called `ireduce` for backwards compatability if a prefix version of `reduce` is ever added.
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To that end, the reduce operator is called `ireduce` for backwards compatability if a `jq` like prefix version of `reduce` is ever added.
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@ -39,8 +39,6 @@ func reduceOperator(d *dataTreeNavigator, context Context, expressionNode *Expre
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return Context{}, err
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return Context{}, err
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}
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}
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accum.SetVariable("context", context.MatchingNodes)
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log.Debugf("with variable %v", variableName)
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log.Debugf("with variable %v", variableName)
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blockExp := expressionNode.Rhs.Rhs
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blockExp := expressionNode.Rhs.Rhs
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@ -14,31 +14,20 @@ var reduceOperatorScenarios = []expressionScenario{
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},
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},
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},
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},
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{
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{
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description: "Convert an array to an object",
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description: "Merge all yaml files together",
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document: `[{name: Cathy, has: apples},{name: Bob, has: bananas}]`,
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document: `a: cat`,
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expression: `.[] as $item ireduce ({}; .[$item | .name] = ($item | .has) )`,
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document2: `b: dog`,
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expected: []string{
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expression: `. as $item ireduce ({}; . * $item )`,
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"D0, P[], (!!map)::Cathy: apples\nBob: bananas\n",
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},
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},
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{
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description: "Merge all documents together - using context",
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subdescription: "The _$context_ variable set by reduce lets you access the data outside the reduce block.",
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document: `a: cat`,
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document2: `b: dog`,
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expression: `fi as $item ireduce ({}; . * ($context | select(fileIndex==$item)) )`,
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expected: []string{
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expected: []string{
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"D0, P[], (!!map)::a: cat\nb: dog\n",
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"D0, P[], (!!map)::a: cat\nb: dog\n",
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},
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},
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},
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},
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{
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{
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description: "Merge all documents together - without using context",
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description: "Convert an array to an object",
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subdescription: "`$context` is just a convenient variable that `reduce` sets, you can use your own for more control",
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document: `[{name: Cathy, has: apples},{name: Bob, has: bananas}]`,
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document: `c: {a: cat}`,
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expression: `.[] as $item ireduce ({}; .[$item | .name] = ($item | .has) )`,
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document2: `c: {b: dog}`,
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expression: `.c as $root | fileIndex as $item ireduce ({}; . * ($root | select(fileIndex==$item)) )`,
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expected: []string{
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expected: []string{
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"D0, P[], (!!map)::{a: cat, b: dog}\n",
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"D0, P[], (!!map)::Cathy: apples\nBob: bananas\n",
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},
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},
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},
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},
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}
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}
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