Table of Contents
What is spark vectorization?
For example, vectorization is used to read multiple rows in a table, or to compute multiple rows at once. So Spark already used vectorization to multiple purposes, which already improves the performance of the Apache Spark program. Vectorized Parquet Reader, Vectorized ORC Reader, Pandas UDF employ Spark.
What is vectorization in database?
Every so often a breakthrough happens that impacts and improves the database industry. The latest is vectorization which, in essence, refers to the process of converting an algorithm from operating on a single value at a time to operating on a set of values at a time.
What is vectorized execution?
The main principle of vectorized execution is batched execu- tion [30] on a columnar data representation: every “work” prim- itive function that manipulates data does not work on a single data item, but on a vector (an array) of such data items that represents multiple tuples.
What is Tez engine in Hive?
Hive embeds Tez so that it can translate complex SQL statements into highly optimized, purpose-built data processing graphs that strike the right balance between performance, throughput, and scalability.
What are the two main types of vector in spark?
The base class of local vectors is Vector , and we provide two implementations: DenseVector and SparseVector .
How do I enable vectorization in spark?
Enable Vectorized Query Execution
- sql. orc. enabled=true – Enables the new ORC format to read/write Spark data source tables and files.
- sql. hive. convertMetastoreOrc=true – Enables the new ORC format to read/write Hive tables.
- sql. orc. char.
What is vectorized reading?
Vectorized Parquet Decoding (aka Vectorized Parquet Reader) allows for reading datasets in parquet format in batches, i.e. rows are decoded in batches. That aims at improving memory locality and cache utilization.
What is YARN and Tez?
YARN manages resources in a Hadoop cluster, based on cluster capacity and load. The Tez execution engine framework efficiently acquires resources from YARN and reuses every component in the pipeline such that no operation is duplicated unnecessarily.
What is difference between MapReduce and Tez?
Tez is a DAG-based system, it’s aware of all opération in such a way that it optimizes these operations before starting execution. MapReduce model simply states that any computation can be performed by two kinds of computation steps – a map step and a reduce step.
What is SerDe 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.
What is the difference between RDD and DataFrame in spark?
3.2. RDD – RDD is a distributed collection of data elements spread across many machines in the cluster. RDDs are a set of Java or Scala objects representing data. DataFrame – A DataFrame is a distributed collection of data organized into named columns. It is conceptually equal to a table in a relational database.
What is the difference between MAP and flatMap transformation?
The map() transformation takes in a function and applies it to each element in the RDD and the result of the function is a new value of each element in the resulting RDD. The flatMap() is used to produce multiple output elements for each input element.
What is vectorized read?
What is vectorization in hive?
Vectorization allows Hive to process a batch of rows together instead of processing one row at a time. Each batch is usually an array of primitive types. Operations are performed on the entire column vector, which improves the instruction pipelines and cache usage.
How to use Vectorized Query Execution in hive CLI?
To use vectorized query execution, you must store your data in ORC format like so: To use vectorized query execution, you must store your data in ORC format. Just follow the below steps: Start Hive CLI and create an ORC table with some data:
What aggregate functions are supported by Hive vectorizer?
Also common aggregate functions such as MIN , MAX, COUNT, AVG, and SUM are also supported. If a function is not supported, the vectorizer attempts to vectorize the function based on the configuration value specified for hive.vectorized.adaptor.usage.mode.
What is Vectorized Query Execution?
In vectorized query execution, data rows are batched together and represented as a set of column vectors. The basic idea of vectorized query execution is to process a batch of rows as an array of column vectors: