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Posted to issues@flink.apache.org by GitBox <gi...@apache.org> on 2019/04/01 23:27:57 UTC
[GitHub] [flink] sunjincheng121 commented on a change in pull request #8087:
[FLINK-12029][table] Add column operations for TableApi
sunjincheng121 commented on a change in pull request #8087: [FLINK-12029][table] Add column operations for TableApi
URL: https://github.com/apache/flink/pull/8087#discussion_r271086764
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File path: docs/dev/table/tableApi.md
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@@ -1682,6 +1682,286 @@ The `OverWindow` defines a range of rows over which aggregates are computed. `Ov
{% top %}
+
+Column Operations
+----------
+
+The column operations are used to select or deselect table columns.
+
+| SYNTAX | DESC |
+| :--------------------- | :-------------------------- |
+| columns(...) | select the specified columns |
+| -columns(...) | deselect the columns specified |
+
+The detailed syntax is as follows:
+
+{% highlight text %}
+columnOperation:
+ [-]columns(columnExprs)
+
+columnExprs:
+ columnExpr [, columnExpr]*
+
+columnExpr:
+ columnRef | columnIndex ~ columnIndex | columnName ~ columnName
+
+columnRef:
+ columnName(The field name that exists in the table) | columnIndex(a positive integer starting from 1)
+{% endhighlight %}
+
+The usage of the column operation is illustrated in the following table. (Suppose we have a table with 5 columns: `(a: Int, b: Long, c: String, d:String, e: String)`):
+
+
+<div class="codetabs" markdown="1">
+<div data-lang="java" markdown="1">
+
+<table class="table table-bordered">
+ <thead>
+ <tr>
+ <th class="text-left" style="width: 20%">Api</th>
+ <th class="text-center">Usage</th>
+ <th class="text-center">Description</th>
+ </tr>
+ </thead>
+ <tbody>
+ <tr>
+ <td>
+ columns(*)|*
+ </td>
+ <td>
+{% highlight java %}
+select("columns(*)") | select("*") = select("a, b, c, d, e")
+{% endhighlight %}
+ </td>
+ <td>
+ all the columns
+ </td>
+ </tr>
+
+ <tr>
+ <td>
+ columns(m ~ n)
+ </td>
+ <td>
+{% highlight java %}
+select("columns(2 ~ 4)") = select("b, c, d")
+{% endhighlight %}
+ </td>
+ <td>
+ columns from m to n
+ </td>
+ </tr>
+
+ <tr>
+ <td>
+ columns(m, n, k)
+ </td>
+ <td>
+{% highlight java %}
+select("columns(1, 3, e)") = select("a, c, e")
+{% endhighlight %}
+ </td>
+ <td>
+ columns m, n, k
+ </td>
+ </tr>
+
+ <tr>
+ <td>
+ columns(m, n ~ k)
+ </td>
+ <td>
+{% highlight java %}
+select("columns(1, 3 ~ 5)") = select("a, c, d ,e")
+{% endhighlight %}
+ </td>
+ <td>
+ mixing of the above two representation
+ </td>
+ </tr>
+
+ <tr>
+ <td>
+ -columns(m ~ n)
+ </td>
+ <td>
+{% highlight java %}
+select("-columns(2 ~ 4)") = select("a, e")
+{% endhighlight %}
+ </td>
+ <td>
+ deselect columns from m to n
+ </td>
+ </tr>
+
+ <tr>
+ <td>
+ -columns(m, n, k)
+ </td>
+ <td>
+{% highlight java %}
+select("-columns(1, 3, 5)") = select("b, d")
+{% endhighlight %}
+ </td>
+ <td>
+ deselect columns m, n, k
+ </td>
+ </tr>
+
+ <tr>
+ <td>
+ -columns(m, n ~ k)
+ </td>
+ <td>
+{% highlight java %}
+select("-columns(1, 3 ~ 5)") = select("b")
+{% endhighlight %}
+ </td>
+ <td>
+ mixing of the above two representation
+ </td>
+ </tr>
+
+ </tbody>
+</table>
+</div>
+
+<div data-lang="scala" markdown="1">
+<table class="table table-bordered">
+ <thead>
+ <tr>
+ <th class="text-left" style="width: 20%">Api</th>
+ <th class="text-center">Usage</th>
+ <th class="text-center">Description</th>
+ </tr>
+ </thead>
+ <tbody>
+ <tr>
+ <td>
+ columns(*)|*
+ </td>
+ <td>
+{% highlight scala %}
+select(columns('*)) | select('*) = select('a, 'b, 'c, 'd, 'e)
+{% endhighlight %}
+ </td>
+ <td>
+ all the columns
+ </td>
+ </tr>
+
+ <tr>
+ <td>
+ columns(m ~ n)
+ </td>
+ <td>
+{% highlight scala %}
+select(columns(2 ~ 4)) = select('b, 'c, 'd)
Review comment:
Please pay an attention on the comments in [google doc ](https://docs.google.com/document/d/1tryl6swt1K1pw7yvv5pdvFXSxfrBZ3_OkOObymis2ck/edit#), Timo suggest tousing some real word instead `~`, Like `to` or `until`, +1 from my side, what do you think?
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