columns selector type #1274
columns selector type #1274
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Jolanrensen
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| ### Column Resolvers | ||
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| `ColumnResolver` is the base type used to access columns within the **Columns Selection DSL**, |
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Maybe not "access" because it can also point to columns that are created on-the-fly like with arithmetics or expr-columns. I think "resolve" is the best way to phrase it.
| ### Column Resolvers | ||
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| `ColumnResolver` is the base type used to access columns within the **Columns Selection DSL**, | ||
| as well as the return type of columns selection expressions. |
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maybe write it like "column(s)", because it's the return type of both the singular and multiple columns dsl
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I use it as generalized name of Dsl
| - **`SingleColumn`** — resolves to a single [`DataColumn`](DataColumn.md). | ||
| - **`ColumnAccessor`** — a specialized `SingleColumn` with a defined path and type argument. | ||
| It can also be renamed during selection. | ||
| - **`ColumnPath`** — a wrapper for [`DataColumn`](DataColumn.md) path |
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*a wrapper for a DataColumn path
| - **`ColumnAccessor`** — a specialized `SingleColumn` with a defined path and type argument. | ||
| It can also be renamed during selection. | ||
| - **`ColumnPath`** — a wrapper for [`DataColumn`](DataColumn.md) path | ||
| in [`DataFrame`](DataFrame.md) also can serve as a `ColumnAccessor`. |
| in [`DataFrame`](DataFrame.md) also can serve as a `ColumnAccessor`. | ||
| ```kotlin | ||
| // Select all columns from the group by path "group2"/"info": | ||
| df.select { pathOf("group2", "info").cols() } |
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.allCols() is better isn't it?
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But what's difference?
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allCols() has compiler plugin support :) cols {} is a filter. (we should probably remove the default { true } predicate in cols, come to think of it.
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okay not yet for column paths, but it's generally good advice when you don't want to filter
| df.group { colsAtAnyDepth().colsOf<String>() } | ||
| .into { it.path.dropLast(2) } | ||
| ``` | ||
| - **`ColumnSet`** — resolves to a list of [`DataColumn`s](DataColumn.md). |
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not sure if we should mention again that this is not really a set, or if it's clear enough when we say it's a list like this.
Try to close #1240