Is there a simple way to output the first few rows of a Flink table to stdout
when developing an application? I just want to see the first 10-20 rows on
screen
during development to make sure my logic is correct.
There doesnt seem to be something like print(10) in the API to see the first
n rows
Here is simple sample program, but I am writing to a CSV table sink for
testing right now.
// Get Customers
String customersPath = "input/customers.csv";
// id,first_name,last_name,email,address,city,state,zip
CsvTableSource customersTableSource = CsvTableSource.builder()
.path(customersPath)
.ignoreFirstLine()
.fieldDelimiter(",")
.field("id", Types.INT())
.field("first_name", Types.STRING())
.field("last_name", Types.STRING())
.field("email", Types.STRING())
.field("address", Types.STRING())
.field("city", Types.STRING())
.field("state", Types.STRING())
.field("zip", Types.STRING())
.build();
// Register our table source
tableEnv.registerTableSource("customers", customersTableSource);
Table customers = tableEnv.scan("customers");
// Perform Operations
// SELECT id,last_name
// FROM customers
Table projection1 = customers
.select("id,last_name")
.filter("last_name !== 'foobar'");
// Write to Sinks
int parallelism = 1;
TableSink<Row> sink = new CsvTableSink("output/customers_out.csv", ",",
parallelism, WriteMode.OVERWRITE);
projection1.writeToSink(sink);
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