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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Whereas normal operators use a demand-driven dataflow iterators calling nextexchanges use data-driven dataflows eager evaluation. You are commenting using your WordPress. Citations Publications citing this paper. A variation on this theme was implemented as part of a parallel sort algorithm: 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.

You are commenting using your Facebook account. Volano parallelism can easily be implemented by inserting one or two exchange operators into a query tree. Sorry, your blog cannot share posts by email.

Encapsulation of Parallelism in the Volcano Query Processing System

A process runs a producer and produces input for the other processes only if it does not have input for the consumer. Thus, the two sort operations are working in parallel. Email required Address never made public.

You are commenting using your Twitter account. The iterators support a simple open-next-close protocol. 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.

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This removes some communication overhead. Notice that it is an iterator with open, next, and close procedures; therefore, it can be inserted at any one place or at multiple places in a complex query tree.

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

For intra-operator parallelism a process group operates on partitions in parallel. The uniform interface between operators makes Volcano extensible by new operators. Semantic Scholar estimates that this publication has citations based on the available data. See our FAQ for additional information. Notify me of new comments via email. The parent process turns to the second sort immediately after forking the child process that will produce the first input in sorted order.

It includes an exchange operator that sustem intra-operator parallelism on partitioned datasets and both vertical and horizontal inter-operator inn.

The next operation requests records from its input tree, possibly sending them off to other processes in the group, until a record for its own partition is found. All other operators are programmed as for single- process execution; the exchange operator encapsulates all parallelism issues, including the translation between demand-driven dataflow within processes and data-driven dataflow between processes, and therefore makes implementation of parallel database algorithms significantly easier and more robust.

Every operator is implemented as an iterator per Hellerstein et al: Showing of extracted citations.

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

Bushy parallelism is also implemented via simple exchange operator insertion: Subscribe never miss an issue! Leave encapwulation Reply Cancel reply Enter your comment here Skip to search form Skip to main content.


You may have picked up on the throwaway line in the Impala paper: The Morning Paper delivered straight to your inbox.

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. An iterator can hold internal state, so that one algorithm operator can be used multiple times in a query.

All operators are designed and coded as if they were meant for a single-process system only. Therefore, if the producers are in danger of overrunning pgocessing consumers, none of the producer operators gets scheduled, and the consumers consume the available records. A uniform interface between operators, e. A propagation tree then forks the other processes needed one per partition:.

Encapsulation of parallelism in the Volcano query processing system

This mode of operation also makes flow control obsolete. This paper has highly influenced 21 other papers. 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.

In Volcano, queries are expressed as complex algebra expressions, and the operators are query processing algorithms.