What is CSVSerde?

What is CSVSerde?

CSVSerde is a magical piece of code, but it isn’t meant to be used for all input CSVs. tl;dr – Use CSVSerde only when you have quoted text or really strange delimiters (such as blanks) in your input data – otherwise you will take a rather substantial performance hit…

How do I add SerDe to my Hive?

Following are the steps to use it:

1. Create a file in local file system called my_table and add following data to it:
2. Start Hive CLI.
3. Add the HCATALOG core file that has JSON SerDe class in it.
4. Create a table to store JSON Data.
5. Load JSON data to this table.
6. Query the data.

How do you escape double quotes in Hive?

The pipe occurring within data fields are enclosed within quotes. Double quotes occurring within data are escaped with \ .

What is row format delimited in Hive?

ROW FORMAT should have delimiters used to terminate the fields and lines like in the above example the fields are terminated with comma (“,”). The default location of Hive table is overwritten by using LOCATION. So the data now is stored in data/weatherext folder inside hive.

Can Athena query CSV?

But unlike Apache Drill, Athena is limited to data only from Amazon’s own S3 storage service. However, Athena is able to query a variety of file formats, including, but not limited to CSV, Parquet, JSON, etc.

What is lazy simple SerDe?

PDFRSS. Specifying this SerDe is optional. This is the SerDe for data in CSV, TSV, and custom-delimited formats that Athena uses by default. This SerDe is used if you don’t specify any SerDe and only specify ROW FORMAT DELIMITED .

Which SerDe is used in hive?

SerDe Overview SerDe is short for Serializer/Deserializer. Hive uses the SerDe interface for IO. The interface handles both serialization and deserialization and also interpreting the results of serialization as individual fields for processing.

Why is SerDe used in hive?

The SerDe interface allows you to instruct Hive about how a record should be processed. A SerDe is a combination of a Serializer and a Deserializer. Hive uses SerDe (and FileFormat) to read and write the table’s row.

How do I remove header from Hive table?

Below is the script for removing the header.

1. CREATE EXTERNAL TABLE IF NOT EXISTS bdp.rmvd_hd_table.
2. (u_name STRING,
3. idf BIGINT,
4. Cn STRING,
5. Ot STRING)
6. ROW FORMAT DELIMITED.
7. FIELDS TERMINATED BY ‘|’
8. STORED AS TEXTFILE.

What is parquet file in Hive?

Apache Parquet is a popular column storage file format used by Hadoop systems, such as Pig, Spark, and Hive. The file format is language independent and has a binary representation. Parquet is used to efficiently store large data sets and has the extension .

Can Athena read ZIP files?

The ZIP file format is not supported. For querying Amazon Kinesis Data Firehose logs from Athena, supported formats include GZIP compression or ORC files with SNAPPY compression.

Is Amazon Athena a database?

Athena is not a database but rather a query engine. This means that: Compute and storage are separate: databases both store data in rest, and provision the resources needed in order to perform queries and calculations. Each of these comes with direct and indirect overheads.

What is regex SerDe?

The Regex SerDe uses a regular expression (regex) to deserialize data by extracting regex groups into table columns. If a row in the data does not match the regex, then all columns in the row are returned as NULL . If a row matches the regex but has fewer groups than expected, the missing groups are NULL .

What is serialization format in Athena?

A SerDe (Serializer/Deserializer) is a way in which Athena interacts with data in various formats. It is the SerDe you specify, and not the DDL, that defines the table schema. In other words, the SerDe can override the DDL configuration that you specify in Athena when you create your table.

What is InputFormat and OutputFormat in Hive?

InputFormat and OutputFormat – allows you to describe you the original data structure so that Hive could properly map it to the table view. SerDe – represents the class which performs actual translation of data from table view to the low level input-output format structures and opposite.

Why is SerDe used?

A SerDe allows Hive to read in data from a table, and write it back out to HDFS in any custom format. Anyone can write their own SerDe for their own data formats. See Hive SerDe for an introduction to SerDes.

How do you check Tblproperties in Hive?

Use these commands to show table properties in Hive:

1. This command will list all the properties for the Sales table: Show tblproperties Sales;
2. The preceding command will list only the property for numFiles in the Sales table: Show partitions Sales (‘numFiles’);