[英]read a data from kafka topic and aggregate using spark tempview?
我想从kafka主题中读取数据,并创建spark tempview以按某些列分组?
+----+--------------------+
| key| value|
+----+--------------------+
|null|{"e":"trade","E":...|
|null|{"e":"trade","E":...|
|null|{"e":"trade","E":...|
但我无法从tempview聚合数据? 值列数据存储为字符串???
Dataset<Row> data = spark
.readStream()
.format("kafka")
.option("kafka.bootstrap.servers", "localhost:9092,localhost:9093")
.option("subscribe", "data2-topic")
.option("startingOffsets", "latest")
.option ("group.id", "test")
.option("enable.auto.commit", "true")
.option("auto.commit.interval.ms", "1000")
.load();
data.selectExpr("CAST(key AS STRING)", "CAST(value AS STRING)");
data.createOrReplaceTempView("Tempdata");
data.show();
Dataset<Row> df2=spark.sql("SELECT e FROM Tempdata group by e");
df2.show();
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