3 research outputs found
Lower Bounds for Multi-Pass Processing of Multiple Data Streams
This paper gives a brief overview of computation models for data stream
processing, and it introduces a new model for multi-pass processing of multiple
streams, the so-called mp2s-automata. Two algorithms for solving the set
disjointness problem wi th these automata are presented. The main technical
contribution of this paper is the proof of a lower bound on the size of memory
and the number of heads that are required for solvin g the set disjointness
problem with mp2s-automata
Trade-offs in Static and Dynamic Evaluation of Hierarchical Queries
We investigate trade-offs in static and dynamic evaluation of hierarchical
queries with arbitrary free variables. In the static setting, the trade-off is
between the time to partially compute the query result and the delay needed to
enumerate its tuples. In the dynamic setting, we additionally consider the time
needed to update the query result under single-tuple inserts or deletes to the
database.
Our approach observes the degree of values in the database and uses different
computation and maintenance strategies for high-degree (heavy) and low-degree
(light) values. For the latter it partially computes the result, while for the
former it computes enough information to allow for on-the-fly enumeration.
We define the preprocessing time, the update time, and the enumeration delay
as functions of the light/heavy threshold. By appropriately choosing this
threshold, our approach recovers a number of prior results when restricted to
hierarchical queries.
We show that for a restricted class of hierarchical queries, our approach
achieves worst-case optimal update time and enumeration delay conditioned on
the Online Matrix-Vector Multiplication Conjecture
Database query processing using finite cursor machines
We introduce a new abstract model of database query processing, finite cursor machines, that incorporates certain data streaming aspects. The model describes quite faithfully what happens in so-called āone-passā and ātwo-pass query processingā. Technically, the model is described in the framework of abstract state machines. Our main results are upper and lower bounds for processing relational algebra queries in this model, specifically, queries of the semijoin fragment of the relational algebra