public Builder setFlushMaxSize(int flushMaxSize) {
            this.flushMaxSize = flushMaxSize;
            return this;
        }
optional, flush max size (includes all append, upsert and delete records),
over this number of records, will flush data.
rdb/rdb-sink/src/main/java/com/dtstack/flink/sql/sink/rdb/format/JDBCUpsertOutputFormat.java