zhengruifeng commented on code in PR #36640:
URL: https://github.com/apache/spark/pull/36640#discussion_r887627360
##########
python/pyspark/sql/session.py:
##########
@@ -611,8 +612,8 @@ def _inferSchema(
:class:`pyspark.sql.types.StructType`
"""
first = rdd.first()
- if not first:
- raise ValueError("The first row in RDD is empty, " "can not infer
schema")
+ if isinstance(first, Sized) and len(first) == 0:
Review Comment:
+1, the `first` job seems unnecessary:
1, `if samplingRatio is None`, we should directly take first 100 non-None
rows, check on the 100 rows and infer the schema;
2, `if samplingRatio is not None`, the `_merge_type` job should be enough.
If we need to check the count, we can add a `count` into `_merge_type`.
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