An amateurs introduction to recursive query processing. In particular, this concerns the corresponding extensions of sql in oracle and db2. The library is designed to formalize relation of nary streams. A query against recursive rules is then translated into a fixpoint functional equation. Parser checks syntax, verifies relations evaluation the queryexecution engine takes a queryevaluation plan, executes that plan, and returns the answers to the query. Overview of query processing scanning, parsing, and semantic analysis query optimization query code generator runtime database processor intermediate form of query execution plan code to execute the query result of query query in highlevel language 1. Datalog and recursive queries, contd ullman slides, pt 2. They are special cases of more general recursive fixpoint queries, which compute transitive closures.
Datalog and recursive query processing now foundations and. Deductive databases have grown out of the desire to combine logic programming with relational databases to. For instance, returning to our party example, we might want to say that our level of con. Recursive query processing has experienced a recent resurgence, as a result of its use in many modern application domains, including data integration, graph analytics, security, program analysis, networking and decision making. Datalog is a query language based on the logic programming paradigm. Keywords topk query processing, probabilistic databases, datalog, firstorder lineage. The interaction between negation and recursion is more tricky and is considered in chapters 14 and 15. But with recursion, datalog can express more than these languages.
The resolution of this fixpoint equation using tarskis theorem leads to efficient computation of the query answer. Recursive processes such as evaluation of a recursive datalog program do not fit the key mapreduce assumption that tasks deliver output only when. To evaluate the idb predicates of recursive datalog rules, we follow the principle. The clauses defining your base cases have to appear first in kb. Wenchao zhou declarative networking is a programming methodology that enables developers to concisely specify network protocols and services, which are directly compiled to a dataflow framework that executes the. Query processing and optimisation lecture 10 introduction. It implements an adhoc query engine using simplified version of general logic programming paradigm. We present the design and evaluation of a datalog engine for execution in graphics processing units gpus.
Comparing columnar, row and array dbmss to process. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. Asynchronous and faulttolerant recursive datalog evaluation. A query processing select a most appropriate plan that is used in responding to a database request.
View notes recursion from bait 470 at rutgers university. Given the wide range of research literature on datalog spanningdecades,weidentifyapracticalsubsetofdatalogbasedonrecent advances in the adoption of datalog. Using a few representative routing protocol examples, we will describe the network datalog 27 language used in declarative networking. From a query processing perspective we consider the three fundamental relational operators.
We address this issue by decomposing databases into a number of subdatabases such that the computation of a program on a database can be achieved by unioning its independent evaluations on the subdatabases. Introduction to data management cse 344 lecture 14. A program with a single datalog rule is a conjunctive query cq for example. For more on the differences between datalog and prolog see what you always wanted to know about datalog and never dared to ask pdf paper. There are four phases in a typical query processing. Datalog and recursive query processing request pdf.
Datalog and recursive query processing surveys for a general audience the datalog language, recursive query processing, and optimization techniques. The engine evaluates recursive and nonrecursive datalog queries using a bottomup approach based on typical relational operators. A rule is defined to be recursive if a predicate symbol appears in the head and also appears in the body as this will require a. Pdf datalog is a subset of prolog and is used as a query language for deductive databases.
An amateurs introduction recursive query processing strategies. It is based on an understanding of the query as a function which maps columns of a relation to other columns. Cn102799624b largescale graph data query method in. Datalog is a subset of the prolog programming language that is used as a query language in deductive databases wiki jatalog is a datalog implementation in java.
A deductive database is a database system that can make deductions i. Introduction to data management cse 344 lecture 15. The invention discloses a largescale graph data query method in a distributed environment based on datalog. Pdf parallel processing of linear recursive datalog queries. A datalog program is a collection of one or more rules.
A long argument in the database community whether recursion should be supported in query languages. Query processing on clusters communicationcost model multiway joins recursion. The present invention provides a method for preprocessing and processing query operation on multiple data chunk on vector enabled architecture. Recursive query processing strategies francots banctlhon 1 raghu ramakrrshnan 1,2 1 mcc 9430 research blvd austin, texas 78759 2 umverslty of texas at austin austin, texas 78712 abstract this paper surveys and compares various strategies for processmg logic queries m rela. Des implements a fixpoint semantics for recursive datalog, finding the least fixpoint as. In the datalog format, relations form the head and body of a datalog query separated by an arrow e. We survey the recent wave of extensions to the popular mapreduce systems, including those that have begun to address the implementation of recursive queries using the same computing environment as mapreduce. Optimizing largescale seminave datalog evaluation in hadoop. Colmerauer conceived prolog for natural language processing and codd conceived ra as a theoretical foundation of relational dbms. Implementation of recursive queries for information systems. In this paper we present recursive query processing capabilities for the objectoriented stack. Java datalog engine with seminaive evaluation and stratified negation.
It provides a parser for the language and an evaluation engine to execute queries that can be embedded into larger applications. Implementation of recursive queries for information. The query execution plan then decides the best and optimized execution plan for execution. A deductive database with datalog and sql query languages.
Cn102799624a largescale graph data query method in. Cluster computing, recursion and datalog request pdf. The same as sql selectfromwhere, without aggregation and grouping. To evaluate the relation reaches, we follow the same iterative process intro.
Datalog and emerging applications proceedings of the. Jiawei han, hongjun lu, some performance results on recursive query processing in relational database systems, proceedings of the second international conference on data engineering, p. On distributed processibility of datalog queries by. Hierarchical and recursive queries in sql wikipedia. Recursive processes such as evaluation of a recursive datalog program do not fit the key mapreduce assumption that. Boon thau loo, wenchao zhou, datalog and recursive query processing, foundations and trends in databases, v. We consider distributed or parallel processing of datalog queries. Datalog and recursion i n part b, we considered query languages ranging from conjunctive queries to. The library is designed to query and formalise relation of nary streams using datalog. It differs from prior surveys written in the eighties and nineties in its comprehensiveness of topics, its coverage of recent developments and applications, and its emphasis on features and techniques beyond classical datalog which are vital for practical applications. Datalog is the language typically used to specify facts, rules and queries in deductive databases. Datalogandrecursive queryprocessing now publishers. We present comprehensive experiments comparing recursive query processing on columnar, row and array dbmss to analyze large graphs with different shape and density.
Datalog and emerging applications proceedings of the 2011. Ddb deductive database 1 outline what is a deductive database system datalog basic inference mechanism for logic programs datalog programs and their. Recursive relations computing and information sciences. A hierarchical query is a type of sql query that handles hierarchical model data. Structured query language is a domainspecific language used in programming and designed for managing data held in a relational database management system rdbms, or for stream processing in a relational data stream management system rdsms. Loo is currently the rca professor of artificial intelligence in the computer and information science department at the university of pennsylvania where he leads a research lab working on distributed systems, and serves as the associate dean of masters and. One of the peculiarities that distinguishes datalog from query languages like relational algebra and calculus is recursion, which gives datalog the capability to express queries like computing a graph transitive closure. Datalog recursions computing sets, then a recursive task can be restarted anyway. Request pdf datalog and recursive query processing in recent years, we have witnessed a revival of the use of recursive queries in a variety of emerging. A popular language used for expressing these queries is datalog. Extending sql or other query language with the transitive closure. Datalog is a declarative database query language with roots in logic programming. Jul 20, 2016 datalog is a subset of the prolog programming language that is used as a query language in deductive databases wiki. In this thesis, we give a detailed description of a bibliographic database, a set of recursive queries, an overview of some standard query processing algorithms, and an implementation of these queries in datalog.
This is an overview of how a query processing works. Jul 27, 2016 datalog is a subset of the prolog programming language that is used as a query language in deductive databases wiki. In recent years, we have witnessed a revival of the use of recursive queries in a variety of emerging application domains such as data in tegrationand exchange,informationextraction,networking,andpro. In recent years, we have witnessed a revival of the use of recursive queries in a variety of emerging application domains such as data in tegration and exchange. Database design, entityrelationship and relational model, relational algebra, query language sql, storage and file structures, query processing, and transaction management. Parsing and translation translate the query into its internal form. The low selectivity of the selection predicate a 10 and an unclustered index on a. Parallel processing of linear recursive datalog queries using transitive closure algorithms. No practical applications of recursive query theory.
The importance of datalog for deductive databases is analogous to that of the conjunctive queries for the relational model. Expressive power of datalog without recursion, datalog can express all and only the queries of core relational algebra. Asynchronous and faulttolerant recursive datalog evaluation in sharednothing engines. It is therefore a necessity for the system to have an efficient algorithm to evaluate these queries. Improve the sql query by using an unsafe datalog rule select distinct l. Sep 25, 2014 query processing would mean the entire process or activity which involves query translation into low level instructions, query optimization to save resources, cost estimation or evaluation of query, and extraction of data from the database. Pdf parallel processing of linear recursive datalog. More specifically, we identify two kinds of distributedprocessible programs according to the. Datalog and recursive query processing now publishers. Topkquery processing in probabilistic databases with non. In this paper we present some engineering solutions for the seminaive evaluation of a linear datalog on hadoopbased systems. Tomasz pieciukiewicz1, krzysztof stencel1,2, kazimierz subieta1 1 polishjapanese institute of information technology, warsaw, poland.
Ecs 165a winter 2011 introduction to database systems. Boon thau loo is a singaporeanamerican computer scientist, university administrator, and businessperson. The library facilitates development of data integration, information exchange and semantic web applications. Query processing is a procedure of transforming a highlevel query such as sql into a correct and efficient execution plan expressed in lowlevel language. The following are three possible reasons why plan b could be faster than plan a. Recursive queries are required for many database applications. One important datalog detail in its sld resolution proof, datalog always chooses the first clause with a matching head it finds in kb what does that mean for recursive function definitions. In recent years, we have witnessed a revival of the use of recursive queries in a variety of emerging application domains such as data integration and exchange, information extraction, networking, and program analysis. The command processor then uses this execution plan to retrieve the data from the database and returns the result. Datalog is a declarative query language for relational databases based on the logic programming paradigm. The query is parsed, optimized, and compiled into a series of mapreduce jobs, using an extended implemenation that directly supports iteration 7. Ddb deductive database 1 outline what is a deductive. Datalog is a subset of the prolog programming language that is used as a query language in deductive databases wiki.
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