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27 commits

Author SHA1 Message Date
Takuya UESHIN 2616d5cc1d [SPARK-35465][PYTHON] Set up the mypy configuration to enable disallow_untyped_defs check for pandas APIs on Spark module
### What changes were proposed in this pull request?

Sets up the `mypy` configuration to enable `disallow_untyped_defs` check for pandas APIs on Spark module.

### Why are the changes needed?

Currently many functions in the main codes in pandas APIs on Spark module are still missing type annotations and disabled `mypy` check `disallow_untyped_defs`.

We should add more type annotations and enable the mypy check.

### Does this PR introduce _any_ user-facing change?

Yes.
This PR adds more type annotations in pandas APIs on Spark module, which can impact interaction with development tools for users.

### How was this patch tested?

The mypy check with a new configuration and existing tests should pass.

Closes #32614 from ueshin/issues/SPARK-35465/disallow_untyped_defs.

Authored-by: Takuya UESHIN <ueshin@databricks.com>
Signed-off-by: Takuya UESHIN <ueshin@databricks.com>
2021-05-21 11:03:35 -07:00
itholic 6b912e4179 [SPARK-35364][PYTHON] Renaming the existing Koalas related codes
### What changes were proposed in this pull request?

There are still naming related to Koalas in test and function name. This PR addressed them to fit pandas-on-spark.
- kdf -> psdf
- kser -> psser
- kidx -> psidx
- kmidx -> psmidx
- to_koalas() -> to_pandas_on_spark()

### Why are the changes needed?

This is because the name Koalas is no longer used in PySpark.

### Does this PR introduce _any_ user-facing change?

`to_koalas()` function is renamed to `to_pandas_on_spark()`

### How was this patch tested?

Tested in local manually.
After changing the related naming, I checked them one by one.

Closes #32516 from itholic/SPARK-35364.

Authored-by: itholic <haejoon.lee@databricks.com>
Signed-off-by: Takuya UESHIN <ueshin@databricks.com>
2021-05-20 15:08:30 -07:00
Xinrong Meng a970f8505d [SPARK-35338][PYTHON] Separate arithmetic operations into data type based structures
### What changes were proposed in this pull request?

The PR is proposed for **pandas APIs on Spark**, in order to separate arithmetic operations shown as below into data-type-based structures.
`__add__, __sub__, __mul__, __truediv__, __floordiv__, __pow__, __mod__,
__radd__, __rsub__, __rmul__, __rtruediv__, __rfloordiv__, __rpow__,__rmod__`

DataTypeOps and subclasses are introduced.

The existing behaviors of each arithmetic operation should be preserved.

### Why are the changes needed?

Currently, the same arithmetic operation of all data types is defined in one function, so it’s difficult to extend the behavior change based on the data types.

Introducing DataTypeOps would be the foundation for [pandas APIs on Spark: Separate basic operations into data type based structures.](https://docs.google.com/document/d/12MS6xK0hETYmrcl5b9pX5lgV4FmGVfpmcSKq--_oQlc/edit?usp=sharing).

### Does this PR introduce _any_ user-facing change?

No.

### How was this patch tested?

Tests are introduced under pyspark.pandas.tests.data_type_ops. One test file per DataTypeOps class.

Closes #32596 from xinrong-databricks/datatypeop_arith_fix.

Authored-by: Xinrong Meng <xinrong.meng@databricks.com>
Signed-off-by: Takuya UESHIN <ueshin@databricks.com>
2021-05-19 19:47:00 -07:00
Takuya UESHIN d44e6c7f10 Revert "[SPARK-35338][PYTHON] Separate arithmetic operations into data type based structures"
This reverts commit d1b24d8aba.
2021-05-19 16:49:47 -07:00
Xinrong Meng d1b24d8aba [SPARK-35338][PYTHON] Separate arithmetic operations into data type based structures
### What changes were proposed in this pull request?

The PR is proposed for **pandas APIs on Spark**, in order to separate arithmetic operations shown as below into data-type-based structures.
`__add__, __sub__, __mul__, __truediv__, __floordiv__, __pow__, __mod__,
__radd__, __rsub__, __rmul__, __rtruediv__, __rfloordiv__, __rpow__,__rmod__`

DataTypeOps and subclasses are introduced.

The existing behaviors of each arithmetic operation should be preserved.

### Why are the changes needed?

Currently, the same arithmetic operation of all data types is defined in one function, so it’s difficult to extend the behavior change based on the data types.

Introducing DataTypeOps would be the foundation for [pandas APIs on Spark: Separate basic operations into data type based structures.](https://docs.google.com/document/d/12MS6xK0hETYmrcl5b9pX5lgV4FmGVfpmcSKq--_oQlc/edit?usp=sharing).

### Does this PR introduce _any_ user-facing change?

No.

### How was this patch tested?

Tests are introduced under pyspark.pandas.tests.data_type_ops. One test file per DataTypeOps class.

Closes #32469 from xinrong-databricks/datatypeop_arith.

Authored-by: Xinrong Meng <xinrong.meng@databricks.com>
Signed-off-by: Takuya UESHIN <ueshin@databricks.com>
2021-05-19 15:05:32 -07:00
Takuya UESHIN 2a335f2d7d [SPARK-34941][PYTHON] Fix mypy errors and enable mypy check for pandas-on-Spark
### What changes were proposed in this pull request?

Fixes `mypy` errors and enables `mypy` check for pandas-on-Spark.

### Why are the changes needed?

The `mypy` check for pandas-on-Spark was disabled when the initial porting.
It should be enabled again; otherwise we will miss type checking errors.

### Does this PR introduce _any_ user-facing change?

No.

### How was this patch tested?

The enabled `mypy` check and existing unit tests should pass.

Closes #32540 from ueshin/issues/SPARK-34941/pandas_mypy.

Authored-by: Takuya UESHIN <ueshin@databricks.com>
Signed-off-by: Takuya UESHIN <ueshin@databricks.com>
2021-05-17 10:46:59 -07:00
Sean Owen a189be8754 [MINOR][DOCS] Avoid some python docs where first sentence has "e.g." or similar
### What changes were proposed in this pull request?

Avoid some python docs where first sentence has "e.g." or similar as the period causes the docs to show only half of the first sentence as the summary.

### Why are the changes needed?

See for example https://spark.apache.org/docs/latest/api/python/reference/api/pyspark.ml.regression.LinearRegressionModel.html?highlight=linearregressionmodel#pyspark.ml.regression.LinearRegressionModel.summary where the method description is clearly truncated.

### Does this PR introduce _any_ user-facing change?

Only changes docs.

### How was this patch tested?

Manual testing of docs.

Closes #32508 from srowen/TruncatedPythonDesc.

Authored-by: Sean Owen <srowen@gmail.com>
Signed-off-by: Hyukjin Kwon <gurwls223@apache.org>
2021-05-12 10:38:59 +09:00
Yikun Jiang 44b7931936 [SPARK-35176][PYTHON] Standardize input validation error type
### What changes were proposed in this pull request?
This PR corrects some exception type when the function input params are failed to validate due to TypeError.
In order to convenient to review, there are 3 commits in this PR:
- Standardize input validation error type on sql
- Standardize input validation error type on ml
- Standardize input validation error type on pandas

### Why are the changes needed?
As suggestion from Python exception doc [1]: "Raised when an operation or function is applied to an object of inappropriate type.", but there are many Value error are raised in some pyspark code, this patch fix them.

[1] https://docs.python.org/3/library/exceptions.html#TypeError

Note that: this patch only addresses the exsiting some wrong raise type for input validation, the input validation decorator/framework which mentioned in [SPARK-35176](https://issues.apache.org/jira/browse/SPARK-35176), would be submited in a speparated patch.

### Does this PR introduce _any_ user-facing change?
Yes, code can raise the right TypeError instead of ValueError.

### How was this patch tested?
Existing test case and UT

Closes #32368 from Yikun/SPARK-35176.

Authored-by: Yikun Jiang <yikunkero@gmail.com>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>
2021-05-03 15:34:24 +09:00
Xinrong Meng 4fcbf59079 [SPARK-35040][PYTHON] Remove Spark-version related codes from test codes
### What changes were proposed in this pull request?

Removes PySpark version dependent codes from pyspark.pandas test codes.

### Why are the changes needed?

There are several places to check the PySpark version and switch the logic, but now those are not necessary.
We should remove them.

We will do the same thing after we finish porting tests.

### Does this PR introduce _any_ user-facing change?

No.

### How was this patch tested?

Existing tests.

Closes #32300 from xinrong-databricks/port.rmv_spark_version_chk_in_tests.

Authored-by: Xinrong Meng <xinrong.meng@databricks.com>
Signed-off-by: Takuya UESHIN <ueshin@databricks.com>
2021-04-22 18:01:07 -07:00
Xinrong Meng 4d2b559d92 [SPARK-34999][PYTHON] Consolidate PySpark testing utils
### What changes were proposed in this pull request?
Consolidate PySpark testing utils by removing `python/pyspark/pandas/testing`, and then creating a file `pandasutils` under `python/pyspark/testing` for test utilities used in `pyspark/pandas`.

### Why are the changes needed?

`python/pyspark/pandas/testing` hold test utilites for pandas-on-spark, and `python/pyspark/testing` contain test utilities for pyspark. Consolidating them makes code cleaner and easier to maintain.

Updated import statements are as shown below:
- from pyspark.testing.sqlutils import SQLTestUtils
- from pyspark.testing.pandasutils import PandasOnSparkTestCase, TestUtils
(PandasOnSparkTestCase is the original ReusedSQLTestCase in `python/pyspark/pandas/testing/utils.py`)

Minor improvements include:
- Usage of missing library's requirement_message
- `except ImportError` rather than `except`
- import pyspark.pandas alias as `ps` rather than `pp`

### Does this PR introduce _any_ user-facing change?

No.

### How was this patch tested?

Unit tests under python/pyspark/pandas/tests.

Closes #32177 from xinrong-databricks/port.merge_utils.

Authored-by: Xinrong Meng <xinrong.meng@databricks.com>
Signed-off-by: Takuya UESHIN <ueshin@databricks.com>
2021-04-22 13:07:35 -07:00
itholic 91bd38467e [SPARK-34995] Port/integrate Koalas remaining codes into PySpark
### What changes were proposed in this pull request?

There are some more changes in Koalas such as [databricks/koalas#2141](c8f803d6be), [databricks/koalas#2143](913d68868d) after the main code porting, this PR is to synchronize those changes with the `pyspark.pandas`.

### Why are the changes needed?

We should port the whole Koalas codes into PySpark and synchronize them.

### Does this PR introduce _any_ user-facing change?

Fixed some incompatible behavior with pandas 1.2.0 and added more to the `to_markdown` docstring.

### How was this patch tested?

Manually tested in local.

Closes #32197 from itholic/SPARK-34995-fix.

Authored-by: itholic <haejoon.lee@databricks.com>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>
2021-04-16 17:42:03 +09:00
Xinrong Meng 4aee19efb4 [SPARK-35032][PYTHON] Port Koalas Index unit tests into PySpark
### What changes were proposed in this pull request?
Now that we merged the Koalas main code into the PySpark code base (#32036), we should port the Koalas Index unit tests to PySpark.

### Why are the changes needed?
Currently, the pandas-on-Spark modules are not tested fully. We should enable the Index unit tests.

### Does this PR introduce _any_ user-facing change?
No.

### How was this patch tested?
Enable Index unit tests.

Closes #32139 from xinrong-databricks/port.indexes_tests.

Authored-by: Xinrong Meng <xinrong.meng@databricks.com>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>
2021-04-16 08:53:30 +09:00
HyukjinKwon 637f59360b Revert "[SPARK-34995] Port/integrate Koalas remaining codes into PySpark"
This reverts commit 9689c44b60.
2021-04-15 21:01:47 +09:00
itholic 9689c44b60 [SPARK-34995] Port/integrate Koalas remaining codes into PySpark
### What changes were proposed in this pull request?

There are some more changes in Koalas such as [databricks/koalas#2141](c8f803d6be), [databricks/koalas#2143](913d68868d) after the main code porting, this PR is to synchronize those changes with the `pyspark.pandas`.

### Why are the changes needed?

We should port the whole Koalas codes into PySpark and synchronize them.

### Does this PR introduce _any_ user-facing change?

Fixed some incompatible behavior with pandas 1.2.0 and added more to the `to_markdown` docstring.

### How was this patch tested?

Manually tested in local.

Closes #32154 from itholic/SPARK-34995.

Authored-by: itholic <haejoon.lee@databricks.com>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>
2021-04-15 19:13:08 +09:00
HyukjinKwon 7ff9d2e3ee [SPARK-35071][PYTHON] Rename Koalas to pandas-on-Spark in main codes
### What changes were proposed in this pull request?

This PR proposes to rename Koalas to pandas-on-Spark in main codes

### Why are the changes needed?

To have the correct name in PySpark. NOTE that the official name in the main documentation will be pandas APIs on Spark to be extra clear. pandas-on-Spark is not the official term.

### Does this PR introduce _any_ user-facing change?

No, it's master-only change. It changes the docstring and class names.

### How was this patch tested?

Manually tested via:

```bash
./python/run-tests --python-executable=python3 --modules pyspark-pandas
```

Closes #32166 from HyukjinKwon/rename-koalas.

Authored-by: HyukjinKwon <gurwls223@apache.org>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>
2021-04-15 12:48:59 +09:00
xinrong-databricks 58feb85145 [SPARK-35034][PYTHON] Port Koalas miscellaneous unit tests into PySpark
### What changes were proposed in this pull request?
Now that we merged the Koalas main code into the PySpark code base (#32036), we should port the Koalas miscellaneous unit tests to PySpark.

### Why are the changes needed?
Currently, the pandas-on-Spark modules are not tested fully. We should enable miscellaneous unit tests.

### Does this PR introduce _any_ user-facing change?
No.

### How was this patch tested?
Enable miscellaneous unit tests.

Closes #32152 from xinrong-databricks/port.misc_tests.

Lead-authored-by: xinrong-databricks <47337188+xinrong-databricks@users.noreply.github.com>
Co-authored-by: Xinrong Meng <xinrong.meng@databricks.com>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>
2021-04-15 11:45:15 +09:00
Takuya UESHIN 4ae57d5b3a [SPARK-35039][PYTHON] Remove PySpark version dependent codes
### What changes were proposed in this pull request?

Removes PySpark version dependent codes from `pyspark.pandas` main codes.

### Why are the changes needed?

There are several places to check the PySpark version and switch the logic, but now those are not necessary.
We should remove them.

We will do the same thing after we finish porting tests.

### Does this PR introduce _any_ user-facing change?

No.

### How was this patch tested?

Existing tests.

Closes #32138 from ueshin/issues/SPARK-35039/pyspark_version.

Authored-by: Takuya UESHIN <ueshin@databricks.com>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>
2021-04-14 14:30:48 +09:00
Xinrong Meng 47d62af2a9 [SPARK-35035][PYTHON] Port Koalas internal implementation unit tests into PySpark
### What changes were proposed in this pull request?
Now that we merged the Koalas main code into the PySpark code base (#32036), we should port the Koalas internal implementation unit tests to PySpark.

### Why are the changes needed?
Currently, the pandas-on-Spark modules are not tested fully. We should enable the internal implementation unit tests.

### Does this PR introduce _any_ user-facing change?
No.

### How was this patch tested?
Enable internal implementation unit tests.

Closes #32137 from xinrong-databricks/port.test_internal_impl.

Lead-authored-by: Xinrong Meng <xinrong.meng@databricks.com>
Co-authored-by: xinrong-databricks <47337188+xinrong-databricks@users.noreply.github.com>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>
2021-04-14 13:59:33 +09:00
Xinrong Meng cd1e8e8158 [SPARK-35033][PYTHON] Port Koalas plot unit tests into PySpark
### What changes were proposed in this pull request?
Now that we merged the Koalas main code into the PySpark code base (#32036), we should port the Koalas plot unit tests to PySpark.

### Why are the changes needed?
Currently, the pandas-on-Spark modules are not tested fully. We should enable the plot unit tests.

### Does this PR introduce _any_ user-facing change?
No.

### How was this patch tested?
Enable plot unit tests.

Closes #32151 from xinrong-databricks/port.plot_tests.

Authored-by: Xinrong Meng <xinrong.meng@databricks.com>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>
2021-04-14 13:20:16 +09:00
Xinrong Meng 8ebc3fca8c [SPARK-35012][PYTHON] Port Koalas DataFrame-related unit tests into PySpark
### What changes were proposed in this pull request?
Now that we merged the Koalas main code into the PySpark code base (#32036), we should port the Koalas DataFrame-related unit tests to PySpark.

### Why are the changes needed?
Currently, the pandas-on-Spark modules are not fully tested. We should enable the DataFrame-related unit tests first.

### Does this PR introduce _any_ user-facing change?
No.

### How was this patch tested?
Enable DataFrame-related unit tests.

Closes #32131 from xinrong-databricks/port.test_dataframe_related.

Lead-authored-by: Xinrong Meng <xinrong.meng@databricks.com>
Co-authored-by: xinrong-databricks <47337188+xinrong-databricks@users.noreply.github.com>
Signed-off-by: Takuya UESHIN <ueshin@databricks.com>
2021-04-13 14:24:08 -07:00
Xinrong Meng a392633566 [SPARK-34996][PYTHON] Port Koalas Series-related unit tests into PySpark
### What changes were proposed in this pull request?
Now that we merged the Koalas main code into the PySpark code base (#32036), we should port the Koalas Series related unit tests to PySpark.

### Why are the changes needed?
Currently, the pandas-on-Spark modules are not fully tested. We should enable the Series related unit tests first.

### Does this PR introduce _any_ user-facing change?
No.

### How was this patch tested?
Enable Series-related unit tests.

Closes #32117 from xinrong-databricks/port.test_series_related.

Lead-authored-by: Xinrong Meng <xinrong.meng@databricks.com>
Co-authored-by: xinrong-databricks <47337188+xinrong-databricks@users.noreply.github.com>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>
2021-04-13 13:03:35 +09:00
Xinrong Meng 9c1f807549 [SPARK-35031][PYTHON] Port Koalas operations on different frames tests into PySpark
### What changes were proposed in this pull request?
Now that we merged the Koalas main code into the PySpark code base (#32036), we should port the Koalas operations on different frames unit tests to PySpark.

### Why are the changes needed?
Currently, the pandas-on-Spark modules are not tested fully. We should enable the operations on different frames unit tests.

### Does this PR introduce _any_ user-facing change?
No.

### How was this patch tested?
Enable operations on different frames unit tests.

Closes #32133 from xinrong-databricks/port.test_ops_on_diff_frames.

Authored-by: Xinrong Meng <xinrong.meng@databricks.com>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>
2021-04-13 11:22:51 +09:00
Luka Sturtewagen fd8081cd27 [SPARK-34983][PYTHON] Renaming the package alias from pp to ps
### What changes were proposed in this pull request?

This PR proposes to fix:

```python
import pyspark.pandas as pp
```

to

```python
import pyspark.pandas as ps
```

### Why are the changes needed?

`pp` might sound offensive in some contexts.

### Does this PR introduce _any_ user-facing change?

The change is in master only. We'll use `ps` as the short name instead of `pp`.

### How was this patch tested?

The CI in this PR will test it out.

Closes #32108 from LSturtew/renaming_pyspark.pandas.

Authored-by: Luka Sturtewagen <luka.sturtewagen@linkit.nl>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>
2021-04-12 11:18:08 +09:00
Takuya UESHIN ff1fc5ed4b [SPARK-34972][PYTHON][TEST][FOLLOWUP] Fix pyspark.pandas doctests which could be flaky
### What changes were proposed in this pull request?

This is a follow-up of #32069.

Makes some doctests which could be flaky skip.

### Why are the changes needed?

Some doctests in `pyspark.pandas` module enabled at #32069 could be flaky because the result row order is nondeterministic.

- groupby-apply with UDF which has a return type annotation will lose its index.
- `Index.symmetric_difference` uses `DataFrame.intersect` and `subtract` internally.

### Does this PR introduce _any_ user-facing change?

No.

### How was this patch tested?

Existing tests.

Closes #32116 from ueshin/issues/SPARK-34972/fix_flaky_tests.

Authored-by: Takuya UESHIN <ueshin@databricks.com>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>
2021-04-11 10:42:00 +09:00
Xinrong Meng 3af2c1bb9c [SPARK-34886][PYTHON] Port/integrate Koalas DataFrame unit test into PySpark
### What changes were proposed in this pull request?
Now that we merged the Koalas main code into the PySpark code base (#32036), we should port the Koalas DataFrame unit test to PySpark.

### Why are the changes needed?
Currently, the pandas-on-Spark modules are not tested at all. We should enable the DataFrame unit test first.

### Does this PR introduce _any_ user-facing change?
No.

### How was this patch tested?
Enable the DataFrame unit test.

Closes #32083 from xinrong-databricks/port.test_dataframe.

Authored-by: Xinrong Meng <xinrong.meng@databricks.com>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>
2021-04-09 15:48:13 +09:00
Takuya UESHIN 2635c3894f [SPARK-34972][PYTHON] Make pandas-on-Spark doctests work
### What changes were proposed in this pull request?

Now that we merged the Koalas main code into PySpark code base (#32036), we should enable doctests on the Spark's infrastructure.

### Why are the changes needed?

Currently the pandas-on-Spark modules are not tested at all.
We should enable doctests first, and we will port other unit tests separately later.

### Does this PR introduce _any_ user-facing change?

No.

### How was this patch tested?

Enabled the whole doctests.

Closes #32069 from ueshin/issues/SPARK-34972/pyspark-pandas_doctests.

Authored-by: Takuya UESHIN <ueshin@databricks.com>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>
2021-04-07 20:50:41 +09:00
itholic caf04f9b77 [SPARK-34890][PYTHON] Port/integrate Koalas main codes into PySpark
### What changes were proposed in this pull request?

As a first step of [SPARK-34849](https://issues.apache.org/jira/browse/SPARK-34849), this PR proposes porting the Koalas main code into PySpark.

This PR contains minimal changes to the existing Koalas code as follows:
1. `databricks.koalas` -> `pyspark.pandas`
2. `from databricks import koalas as ks` -> `from pyspark import pandas as pp`
3. `ks.xxx -> pp.xxx`

Other than them:
1. Added a line to `python/mypy.ini` in order to ignore the mypy test. See related issue at [SPARK-34941](https://issues.apache.org/jira/browse/SPARK-34941).
2. Added a comment to several lines in several files to ignore the flake8 F401. See related issue at [SPARK-34943](https://issues.apache.org/jira/browse/SPARK-34943).

When this PR is merged, all the features that were previously used in [Koalas](https://github.com/databricks/koalas) will be available in PySpark as well.

Users can access to the pandas API in PySpark as below:

```python
>>> from pyspark import pandas as pp
>>> ppdf = pp.DataFrame({"A": [1, 2, 3], "B": [15, 20, 25]})
>>> ppdf
   A   B
0  1  15
1  2  20
2  3  25
```

The existing "options and settings" in Koalas are also available in the same way:

```python
>>> from pyspark.pandas.config import set_option, reset_option, get_option
>>> ppser1 = pp.Series([1, 2, 3])
>>> ppser2 = pp.Series([3, 4, 5])
>>> ppser1 + ppser2
Traceback (most recent call last):
...
ValueError: Cannot combine the series or dataframe because it comes from a different dataframe. In order to allow this operation, enable 'compute.ops_on_diff_frames' option.

>>> set_option("compute.ops_on_diff_frames", True)
>>> ppser1 + ppser2
0    4
1    6
2    8
dtype: int64
```

Please also refer to the [API Reference](https://koalas.readthedocs.io/en/latest/reference/index.html) and [Options and Settings](https://koalas.readthedocs.io/en/latest/user_guide/options.html) for more detail.

**NOTE** that this PR intentionally ports the main codes of Koalas first almost as are with minimal changes because:
- Koalas project is fairly large. Making some changes together for PySpark will make it difficult to review the individual change.
    Koalas dev includes multiple Spark committers who will review. By doing this, the committers will be able to more easily and effectively review and drive the development.
- Koalas tests and documentation require major changes to make it look great together with PySpark whereas main codes do not require.
- We lately froze the Koalas codebase, and plan to work together on the initial porting. By porting the main codes first as are, it unblocks the Koalas dev to work on other items in parallel.

I promise and will make sure on:
- Rename Koalas to PySpark pandas APIs and/or pandas-on-Spark accordingly in documentation, and the docstrings and comments in the main codes.
- Triage APIs to remove that don’t make sense when Koalas is in PySpark

The documentation changes will be tracked in [SPARK-34885](https://issues.apache.org/jira/browse/SPARK-34885), the test code changes will be tracked in [SPARK-34886](https://issues.apache.org/jira/browse/SPARK-34886).

### Why are the changes needed?

Please refer to:
- [[DISCUSS] Support pandas API layer on PySpark](http://apache-spark-developers-list.1001551.n3.nabble.com/DISCUSS-Support-pandas-API-layer-on-PySpark-td30945.html)
- [[VOTE] SPIP: Support pandas API layer on PySpark](http://apache-spark-developers-list.1001551.n3.nabble.com/VOTE-SPIP-Support-pandas-API-layer-on-PySpark-td30996.html)

### Does this PR introduce _any_ user-facing change?

Yes, now users can use the pandas APIs on Spark

### How was this patch tested?

Manually tested for exposed major APIs and options as described above.

### Koalas contributors

Koalas would not have been possible without the following contributors:

ueshin
HyukjinKwon
rxin
xinrong-databricks
RainFung
charlesdong1991
harupy
floscha
beobest2
thunterdb
garawalid
LucasG0
shril
deepyaman
gioa
fwani
90jam
thoo
AbdealiJK
abishekganesh72
gliptak
DumbMachine
dvgodoy
stbof
nitlev
hjoo
gatorsmile
tomspur
icexelloss
awdavidson
guyao
akhilputhiry
scook12
patryk-oleniuk
tracek
dennyglee
athena15
gstaubli
WeichenXu123
hsubbaraj
lfdversluis
ktksq
shengjh
margaret-databricks
LSturtew
sllynn
manuzhang
jijosg
sadikovi

Closes #32036 from itholic/SPARK-34890.

Authored-by: itholic <haejoon.lee@databricks.com>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>
2021-04-06 12:42:39 +09:00