Parquet SerDe
Verwenden Sie den Parquet SerDe, um Athena-Tabellen aus Parquet-Daten zu erstellen.
Parquet Hive SerDe wird für im Parquet-Format
Name der Serialisierungsbibliothek
Der Name der Serialisierungsbibliothek für den Parquet SerDe lautet org.apache.hadoop.hive.ql.io.parquet.serde.ParquetHiveSerDe. Informationen zum Quellcode finden Sie unter Class ParquetHiveSerDe
Anmerkung
Ersetzen Sie myregion in s3://athena-examples- durch den Regionsbezeichner, in dem Sie Athena ausführen, z. B. myregion/path/to/data/s3://athena-examples-us-west-1/path/to/data/.
Verwenden Sie die folgende CREATE TABLE-Anweisung zum Erstellen einer Athena-Tabelle basierend auf den in Amazon S3 in Parquet-Format gespeicherten Daten:
CREATE EXTERNAL TABLE flight_delays_pq ( yr INT, quarter INT, month INT, dayofmonth INT, dayofweek INT, flightdate STRING, uniquecarrier STRING, airlineid INT, carrier STRING, tailnum STRING, flightnum STRING, originairportid INT, originairportseqid INT, origincitymarketid INT, origin STRING, origincityname STRING, originstate STRING, originstatefips STRING, originstatename STRING, originwac INT, destairportid INT, destairportseqid INT, destcitymarketid INT, dest STRING, destcityname STRING, deststate STRING, deststatefips STRING, deststatename STRING, destwac INT, crsdeptime STRING, deptime STRING, depdelay INT, depdelayminutes INT, depdel15 INT, departuredelaygroups INT, deptimeblk STRING, taxiout INT, wheelsoff STRING, wheelson STRING, taxiin INT, crsarrtime INT, arrtime STRING, arrdelay INT, arrdelayminutes INT, arrdel15 INT, arrivaldelaygroups INT, arrtimeblk STRING, cancelled INT, cancellationcode STRING, diverted INT, crselapsedtime INT, actualelapsedtime INT, airtime INT, flights INT, distance INT, distancegroup INT, carrierdelay INT, weatherdelay INT, nasdelay INT, securitydelay INT, lateaircraftdelay INT, firstdeptime STRING, totaladdgtime INT, longestaddgtime INT, divairportlandings INT, divreacheddest INT, divactualelapsedtime INT, divarrdelay INT, divdistance INT, div1airport STRING, div1airportid INT, div1airportseqid INT, div1wheelson STRING, div1totalgtime INT, div1longestgtime INT, div1wheelsoff STRING, div1tailnum STRING, div2airport STRING, div2airportid INT, div2airportseqid INT, div2wheelson STRING, div2totalgtime INT, div2longestgtime INT, div2wheelsoff STRING, div2tailnum STRING, div3airport STRING, div3airportid INT, div3airportseqid INT, div3wheelson STRING, div3totalgtime INT, div3longestgtime INT, div3wheelsoff STRING, div3tailnum STRING, div4airport STRING, div4airportid INT, div4airportseqid INT, div4wheelson STRING, div4totalgtime INT, div4longestgtime INT, div4wheelsoff STRING, div4tailnum STRING, div5airport STRING, div5airportid INT, div5airportseqid INT, div5wheelson STRING, div5totalgtime INT, div5longestgtime INT, div5wheelsoff STRING, div5tailnum STRING ) PARTITIONED BY (year STRING) STORED AS PARQUET LOCATION 's3://athena-examples-myregion/flight/parquet/' tblproperties ("parquet.compression"="SNAPPY");
Führen Sie die MSCK REPAIR TABLE-Anweisung auf der Tabelle aus, um die Partitionsmetadaten zu aktualisieren:
MSCK REPAIR TABLE flight_delays_pq;
Fragen Sie die 10 Routen ab, bei denen es zu einer Verzögerung von mehr als 1 Stunde kam:
SELECT origin, dest, count(*) as delays FROM flight_delays_pq WHERE depdelayminutes > 60 GROUP BY origin, dest ORDER BY 3 DESC LIMIT 10;
Anmerkung
Die Flugtabellendaten stammen aus Flügen
Parquet-Statistiken ignorieren
Wenn Sie Parquet-Daten lesen, erhalten Sie möglicherweise Fehlermeldungen wie die folgenden:
HIVE_CANNOT_OPEN_SPLIT: Index x out of bounds for length y HIVE_CURSOR_ERROR: Failed to read x bytes HIVE_CURSOR_ERROR: FailureException at Malformed input: offset=x HIVE_CURSOR_ERROR: FailureException at java.io.IOException: can not read class org.apache.parquet.format.PageHeader: Socket is closed by peer.
Um dieses Problem zu umgehen, verwenden Sie die CREATE TABLE- oder ALTER TABLE SET
TBLPROPERTIES-Anweisung, um die Parquet-SerDe-Eigenschaft parquet.ignore.statistics auf true zu setzen, wie in den folgenden Beispielen.
Beispiel für CREATE TABLE
... ROW FORMAT SERDE 'org.apache.hadoop.hive.ql.io.parquet.serde.ParquetHiveSerDe' WITH SERDEPROPERTIES ( 'parquet.ignore.statistics'='true') STORED AS PARQUET ...
Beispiel für ALTER TABLE
ALTER TABLE ... SET TBLPROPERTIES ('parquet.ignore.statistics'='true')