BUG: Fixed merging on tz-aware
State: closed

Closes https://github.com/pandas-dev/pandas/issues/25014


Labels:
name: Reshaping
description: Concat, Merge/Join, Stack/Unstack, Explode
name: Timezones
description: Timezone data dtype

Comments:
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25033?src=pr&el=h1) Report
> Merging [#25033](https://codecov.io/gh/pandas-dev/pandas/pull/25033?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/b9f2e2bd526ad69fe3d737d395742193e29fd0e5?src=pr&el=desc) will **decrease** coverage by `49.49%`.
> The diff coverage is `50%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/25033/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/25033?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #25033      +/-   ##
==========================================
- Coverage   92.38%   42.88%   -49.5%     
==========================================
  Files         166      166              
  Lines       52401    52403       +2     
==========================================
- Hits        48409    22472   -25937     
- Misses       3992    29931   +25939
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `?` | |
| #single | `42.88% <50%> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/25033?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/internals/concat.py](https://codecov.io/gh/pandas-dev/pandas/pull/25033/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW50ZXJuYWxzL2NvbmNhdC5weQ==) | `73.04% <50%> (-23.41%)` | :arrow_down: |
| [pandas/io/formats/latex.py](https://codecov.io/gh/pandas-dev/pandas/pull/25033/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2Zvcm1hdHMvbGF0ZXgucHk=) | `0% <0%> (-100%)` | :arrow_down: |
| [pandas/core/categorical.py](https://codecov.io/gh/pandas-dev/pandas/pull/25033/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvY2F0ZWdvcmljYWwucHk=) | `0% <0%> (-100%)` | :arrow_down: |
| [pandas/io/sas/sas\_constants.py](https://codecov.io/gh/pandas-dev/pandas/pull/25033/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL3Nhcy9zYXNfY29uc3RhbnRzLnB5) | `0% <0%> (-100%)` | :arrow_down: |
| [pandas/tseries/plotting.py](https://codecov.io/gh/pandas-dev/pandas/pull/25033/diff?src=pr&el=tree#diff-cGFuZGFzL3RzZXJpZXMvcGxvdHRpbmcucHk=) | `0% <0%> (-100%)` | :arrow_down: |
| [pandas/tseries/converter.py](https://codecov.io/gh/pandas-dev/pandas/pull/25033/diff?src=pr&el=tree#diff-cGFuZGFzL3RzZXJpZXMvY29udmVydGVyLnB5) | `0% <0%> (-100%)` | :arrow_down: |
| [pandas/io/formats/html.py](https://codecov.io/gh/pandas-dev/pandas/pull/25033/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2Zvcm1hdHMvaHRtbC5weQ==) | `0% <0%> (-99.35%)` | :arrow_down: |
| [pandas/core/groupby/categorical.py](https://codecov.io/gh/pandas-dev/pandas/pull/25033/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ3JvdXBieS9jYXRlZ29yaWNhbC5weQ==) | `0% <0%> (-95.46%)` | :arrow_down: |
| [pandas/io/sas/sas7bdat.py](https://codecov.io/gh/pandas-dev/pandas/pull/25033/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL3Nhcy9zYXM3YmRhdC5weQ==) | `0% <0%> (-91.17%)` | :arrow_down: |
| [pandas/io/sas/sas\_xport.py](https://codecov.io/gh/pandas-dev/pandas/pull/25033/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL3Nhcy9zYXNfeHBvcnQucHk=) | `0% <0%> (-90.15%)` | :arrow_down: |
| ... and [124 more](https://codecov.io/gh/pandas-dev/pandas/pull/25033/diff?src=pr&el=tree-more) | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25033?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25033?src=pr&el=footer). Last update [b9f2e2b...8bd020f](https://codecov.io/gh/pandas-dev/pandas/pull/25033?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25033?src=pr&el=h1) Report
> Merging [#25033](https://codecov.io/gh/pandas-dev/pandas/pull/25033?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/b9f2e2bd526ad69fe3d737d395742193e29fd0e5?src=pr&el=desc) will **increase** coverage by `<.01%`.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/25033/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/25033?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #25033      +/-   ##
==========================================
+ Coverage   92.38%   92.38%   +<.01%     
==========================================
  Files         166      166              
  Lines       52401    52401              
==========================================
+ Hits        48409    48410       +1     
+ Misses       3992     3991       -1
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.8% <100%> (ø)` | :arrow_up: |
| #single | `42.87% <0%> (-0.01%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/25033?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/internals/concat.py](https://codecov.io/gh/pandas-dev/pandas/pull/25033/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW50ZXJuYWxzL2NvbmNhdC5weQ==) | `96.45% <100%> (ø)` | :arrow_up: |
| [pandas/util/testing.py](https://codecov.io/gh/pandas-dev/pandas/pull/25033/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvdGVzdGluZy5weQ==) | `88.13% <0%> (+0.09%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25033?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25033?src=pr&el=footer). Last update [b9f2e2b...43706fb](https://codecov.io/gh/pandas-dev/pandas/pull/25033?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).

lgtm. ping on green.
All green, but had to make an additional change in 
https://github.com/pandas-dev/pandas/pull/25033/commits/43706fb512ac75afd7999ad2198d5f08dfde7ce8
thanks @TomAugspurger