Maxim Gekk created SPARK-25396:
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Summary: Read array of JSON objects via an Iterator
Key: SPARK-25396
URL: https://issues.apache.org/jira/browse/SPARK-25396
Project: Spark
Issue Type: Improvement
Components: SQL
Affects Versions: 2.4.0
Reporter: Maxim Gekk
If a JSON file has a structure like below:
{code}
[
{
"time":"2018-08-13T18:00:44.0860000Z",
"resourceId":"some-text",
"category":"A",
"level":2,
"operationName":"Error",
"properties":{...}
},
{
"time":"2018-08-14T18:00:44.0860000Z",
"resourceId":"some-text2",
"category":"B",
"level":3,
"properties":{...}
},
]
{code}
it should be read in the `multiLine` mode. In this mode, Spark read whole array
into memory in both cases when schema is `ArrayType` and `StructType`. It can
lead to unnecessary memory consumption and even to OOM for big JSON files.
In general, there is no need to materialize all parsed JSON record in memory
there:
https://github.com/apache/spark/blob/a8a1ac01c4732f8a738b973c8486514cd88bf99b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/json/JacksonParser.scala#L88-L95
. So, JSON objects of an array can be read via an Iterator.
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