[jira] [Commented] (ARROW-1632) [Python] Permit categorical conversions in Table.to_pandas on a per-column basis

[ASF GitHub Bot (JIRA)]

    [ 
https://issues.apache.org/jira/browse/ARROW-1632?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16370677#comment-16370677
 ] 

ASF GitHub Bot commented on ARROW-1632:
---------------------------------------

wesm commented on a change in pull request #1620: ARROW-1632: [Python] Permit 
categorical conversions in Table.to_pandas on a per-column basis
URL: https://github.com/apache/arrow/pull/1620#discussion_r169481823
 
 

 ##########
 File path: cpp/src/arrow/python/arrow_to_pandas.cc
 ##########
 @@ -1771,7 +1790,33 @@ Status ConvertColumnToPandas(PandasOptions options, 
const std::shared_ptr<Column
 
 Status ConvertTableToPandas(PandasOptions options, const 
std::shared_ptr<Table>& table,
                             int nthreads, MemoryPool* pool, PyObject** out) {
-  DataFrameBlockCreator helper(options, table, pool);
+  return ConvertTableToPandas(options, std::unordered_set<std::string>(), 
table, nthreads,
+                              pool, out);
+}
+
+Status ConvertTableToPandas(PandasOptions options,
+                            const std::unordered_set<std::string>& 
categorical_columns,
+                            const std::shared_ptr<Table>& table, int nthreads,
+                            MemoryPool* pool, PyObject** out) {
+  std::shared_ptr<Table> current_table = table;
+  if (!categorical_columns.empty()) {
+    FunctionContext ctx;
+    for (int i = 0; i < table->num_columns(); i++) {
+      const Column& col = *table->column(i);
+      if (categorical_columns.count(col.name())) {
+        Datum out;
+        DictionaryEncode(&ctx, Datum(col.data()), &out);
+        std::shared_ptr<ChunkedArray> array = out.chunked_array();
+        auto field = std::make_shared<Field>(
+            col.name(), array->type(), col.field()->nullable(), 
col.field()->metadata());
+        auto column = std::make_shared<Column>(field, array);
+        current_table->RemoveColumn(i, &current_table);
+        current_table->AddColumn(i, column, &current_table);
 
 Review comment:
   Need to check Status in these two lines

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> [Python] Permit categorical conversions in Table.to_pandas on a per-column 
> basis
> --------------------------------------------------------------------------------
>
>                 Key: ARROW-1632
>                 URL: https://issues.apache.org/jira/browse/ARROW-1632
>             Project: Apache Arrow
>          Issue Type: Improvement
>          Components: Python
>            Reporter: Wes McKinney
>            Assignee: Uwe L. Korn
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 0.9.0
>
>
> Currently this is all or nothing



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