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Christina Teflioudi

Paul Willems

Till Merker

Marius Eich

A database execution engine generates a first query execution plan in response to receiving a first query, where a thread limit is specified for worker threads launched by the database execution engine. A first main executor thread is launched to process the first query and a first plurality of tasks are created to be performed in response to the first query. Then, a first plurality of worker threads are launched to perform the first plurality of tasks, where the first plurality of worker threads is less than or equal to the thread limit. In response to parallelizing processing of the first query execution plan, the first main executor thread is restricted to a first period of execution time before entering a waiting phase. The first main executor thread is woken up after the first plurality of worker threads have completed the first plurality of tasks.

Reducing activity of the main SQL executor thread

In some implementations, there is provided a method that includes receiving a query request including a top k query operator for query plan generation, optimization, and execution, wherein k defines a threshold limit of query results for the top k query operator; inserting into a query plan a check operator associated with the top k query operator; in response to executing the query plan, checking, by the check operator, whether an early exit occurs due to the top k query operator reaching the threshold limit; in response to the early exit occurring due to the top k query operator reaching the threshold limit, stopping processing, by the check operator, including opening of another fragment of a database table; and in response to the early exit not occurring, allowing, by the check operator, the opening of the other fragment of the database table.

Custom table scan for top k queries

In some example embodiments, there is provided a method that includes receiving a query for query plan generation and query plan optimization; detecting whether the query plan includes a restart pipeline, the restart pipeline including one or more first operators that cause a query plan restart; detecting whether the query plan includes a result pipeline, the result pipeline including one or more second operators that provide result streaming; determining whether there is a dependency between execution of the restart pipeline and execution of the result pipeline; in response to determining there is no dependency, reordering the restart pipeline in the query plan such that the restart pipeline will be executed before the result pipeline in order to enable result streaming optimization; and providing the reordered query plan for execution. Related systems and computer program products are also provided.

Result streaming by reordering pipelines

A method for allocating worker threads may include receiving a first fetch call for a query accessing a dataset stored at a database. The first fetch call may require a first portion of a result for the query. A first quantity of worker threads may be allocated to generate the first portion of the result for the query in response to the first fetch call. In response to a second fetch call for the query by determining a threshold corresponding to the first quantity of worker threads, a second quantity of data required for the second fetch call, and a third quantity of data buffered from the first fetch call. A second quantity of worker threads to generate a second portion of the result for the query may be allocated based on the threshold. Related systems and computer program products are also provided.

Allocation of worker threads in a parallelization framework with result streaming

A method for executing a dynamically generated operation in a parallel processing framework may include executing the dynamically generated operation sequentially for a threshold quantity of times before initiating a compilation operation to generate precompiled code for the dynamically generated operation. Upon generating the precompiled code, execution of the precompiled code may be parallelized by determining, based on a quantity of time required to execute the precompiled code on a portion of a dataset, a task size. The execution of the precompiled code may be divided, based on the task size, into one or more tasks. Moreover, a corresponding quantity of worker threads may be allocated to perform the one or more tasks in parallel. Related methods and computer program products are also provided.

Dynamically generated operations in a parallel processing framework

Aspects of the current subject matter are directed to providing query results to clients by incorporating pause and/or detach operations into the query execution after a first fetch of results. The pause and the detach operations for query execution consistent with implementations of the current subject matter result in reduced times and conserved resources in providing query results by computing only results necessary to satisfy a first fetch call prior to computing results necessary to satisfy subsequent fetch calls.

Query execution including pause and detach operations after first data fetch

Aspects of the current subject matter are directed to executing queries on tables in which one or more columns contain a single value. Upon execution of a query, columns in which a single value is contained are identified, and a pre-compiled code entry containing relevant identifying information is compiled as part of a query execution plan. The query execution plan is used for subsequent query executions, alleviating the need to access the columns during the subsequent query executions that involve the columns. A fingerprint value may be used to track if changes to relevant tables occur.

Query plan generation and execution based on single value columns

In some aspects, there is provided a method that may include: intercepting a query requiring access to data stored in a table. The query may include an identifier, which may be associated with a row of the table and a reference to a column of the table. The method may further include preparing a table object to enable access to the data stored in the row and the column of the table. The preparing may include locating the row associated with the identifier. The preparing may further include acquiring locks for the data stored in the located row and the column in the row. The method may also include executing the query upon preparing the table object. Related systems, methods, and articles of manufacture are also described.

Take over table opening for operators

A query is received at a database execution engine. The query is executed by the database execution engine, the executing including executing one or more threads that operate on versions of data of the delta fragment; acquiring and releasing, by a first thread, a latch on a first version of the data of the delta fragment, the releasing is performed prior to the first thread entering a wait state; and reclaiming the first version of the data of the delta fragment from memory and during execution of the query. Related systems, methods, and articles of manufacture are also described.

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Heidelberg, Germany

Christina Teflioudi