Graefe, Goetz, “Encapsulation of Parallelism in the Volcano Query Processing System ; CU-CS” (). Computer Science Technical Reports. Encapsulation of parallelism in the volcano query processing system – Graefe ‘ You may have picked up on the throwaway line in the Impala. Encapsulation of Parallelism in the Volcano Query Processing System (). The Volcano query processing system uses the operator model of query.

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For example, in order to sort two inputs into a merge-join in parallel, the first or both inputs are separated from the merge-join by an exchange operation.

We call this concept anonymous inputs or streams … Streams represent the most efficient execution model in terms of time overhead for sychronizing operators and space number of records that systtem reside in memory concurrently for single process query evaluation.

An operator does not need to know what kind of operator produces its input, and whether its input comes from a complex query or from a simple file scan. HellersteinEric A. Twitter LinkedIn Email Print.

Encapsulation of parallelism in the Volcano query processing system

The exchange operator in the consumer process acts as a normal iterator, the only difference from other iterators is that it receives its input via inter-process communication. Every operator is implemented as an iterator per Hellerstein et al: Learn how your comment data is processed.

Notify me of new posts via email. Bushy parallelism can easily be implemented by inserting one or two exchange operators into a query tree. Leave a Reply Cancel reply Enter your comment here The Morning Paper delivered straight to your inbox.


This removes some communication overhead. This paper has highly influenced 21 other papers. Showing of extracted citations. Bushy parallelism is also implemented via simple exchange operator insertion: Skip to search form Skip to main content. When the query tree is opened the first process is the master.

The exchange operator can be used to implement pipelined parallelism called vertical parallelism in the paperbushy parallelism processing different subtrees of a complex query tree in paralleland intra-operator parallelism partitioning the dataset and processing partitions in parallel for a single operator.

The iterators support a simple open-next-close protocol. The module responsible for parallel execution and synchronization is the exchange iterator.

Encapsulation of Parallelism in the Volcano Query Processing System

The uniform interface between operators makes Volcano extensible by new operators. Subscribe never miss an issue! When attempting to parallelize Volcano, prrocessing had to choose between two models of parallelization, called here the bracket and operator models.

Therefore, if the producers are in danger of overrunning the consumers, none of the producer operators gets scheduled, and the consumers consume the available records. An iterator can hold internal state, so prallelism one algorithm operator can be used multiple times in a query.

In such a scheme, the master forks one slave, then both fork a new slave each, then all four fork a new slave each, etc.

Encapsulation of Parallelism in the Volcano Query Processing System – Semantic Scholar

A propagation tree then forks the other processes needed one per partition: From This Paper Topics from this paper. A uniform interface between operators, e. For intra-operator parallelism a process group operates on partitions in parallel.

Citation Statistics Citations 0 10 20 30 ’90 ’96 ’03 ’10 ‘ The next operation requests records from vllcano input tree, possibly sending them off to other processes in the group, until a record for its own partition is found. This scheme has been used very effectively for broadcast communication and synchronization in binary hypercubes.


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Encapsulation of parallelism in the Volcano query processing system | the morning paper

It includes an exchange operator that allows intra-operator parallelism on partitioned datasets quer both vertical and horizontal inter-operator parallelism. A variation on this theme was implemented as part of a parallel sort algorithm: This site uses Akismet to reduce spam.

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This mode of operation also makes flow control obsolete. When the exchange operator is opened, it does not fork any processes but establishes a communication port for data exchange. The key benefit of the exchange operator technique is that is allows query processing algorithms to be coded for single-process execution but run in a highly parallel environment without modifications. Email required Address never made public. Sorry, your blog cannot share posts by email.

Citations Publications citing this paper. You are commenting using your Facebook account. Topics Discussed in This Paper. The parent process turns to the second sort immediately after forking the child process that will produce the first input in sorted order. Thus, the two sort operations are working in parallel.