GitHub user HyukjinKwon opened a pull request:
https://github.com/apache/spark/pull/14028
[SPARK-16351][SQL] Avoid record-per type dispatch in JSON when writing
## What changes were proposed in this pull request?
Currently, `JacksonGenerator.apply` is doing type-based dispatch for each
row to write appropriate values.
It might not have to be done like this because the schema is already kept.
So, appropriate writers can be created first according to the schema, and
then apply them to each row. This approach is similar with
`CatalystWriteSupport`.
This PR corrects `JacksonGenerator` so that it creates some writes for the
schema and then applies them to each row rather than every time.
Benchmark was proceeded with the codes below:
```
test("Benchmark for JSON writer") {
val N = 500 << 8
val row =
"""{"struct":{"field1": true, "field2": 92233720368547758070},
"structWithArrayFields":{"field1":[4, 5, 6], "field2":["str1",
"str2"]},
"arrayOfString":["str1", "str2"],
"arrayOfInteger":[1, 2147483647, -2147483648],
"arrayOfLong":[21474836470, 9223372036854775807,
-9223372036854775808],
"arrayOfBigInteger":[922337203685477580700, -922337203685477580800],
"arrayOfDouble":[1.2, 1.7976931348623157E308, 4.9E-324,
2.2250738585072014E-308],
"arrayOfBoolean":[true, false, true],
"arrayOfNull":[null, null, null, null],
"arrayOfStruct":[{"field1": true, "field2": "str1"}, {"field1":
false}, {"field3": null}],
"arrayOfArray1":[[1, 2, 3], ["str1", "str2"]],
"arrayOfArray2":[[1, 2, 3], [1.1, 2.1, 3.1]]
}"""
val df =
spark.sqlContext.read.json(spark.sparkContext.parallelize(List.fill(N)(row)))
(0 to 10).foreach { _ =>
val benchmark = new Benchmark("JSON writer", N)
benchmark.addCase("writing JSON file", 10) { iter =>
withTempPath { path =>
df.write.format("json").save(path.getCanonicalPath)
}
}
benchmark.run()
}
}
```
This produced the results below
- **Before**
```
JSON writer: Best/Avg Time(ms) Rate(M/s)
Per Row(ns) Relative
------------------------------------------------------------------------------------------------
writing JSON file 1675 / 1767 0.1
13087.5 1.0X
```
- **After**
```
JSON writer: Best/Avg Time(ms) Rate(M/s)
Per Row(ns) Relative
------------------------------------------------------------------------------------------------
writing JSON file 1597 / 1686 0.1
12477.1 1.0X
```
In addition, I ran this benchmarks 10 times for each and calculated the
average times as below:
| **Before** | **After**|
|---------------|------------|
|17478ms |16669ms |
It seems roughly ~5% is improved.
## How was this patch tested?
Existing tests should cover this.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/HyukjinKwon/spark SPARK-16351
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/14028.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #14028
----
commit 76ca05a383b1b3f6deea266276af872ab3a18f36
Author: hyukjinkwon <gurwls...@gmail.com>
Date: 2016-07-02T12:16:25Z
Avoid record-per type dispatch in JSON when writing
commit 34ec476b5afad926db89a03ff64e6cda8263ee86
Author: hyukjinkwon <gurwls...@gmail.com>
Date: 2016-07-02T12:18:03Z
Keep the comment
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