Morton M. Astrahan’s research while affiliated with IBM and other places

We have described the architecture of System R, including the Relational Data System and the Research Storage System. The RDS supports a flexible spectrum of binding times, ranging from precompilation of “canned transactions” to on-line execution of ad hoc queries. The advantages of this approach may be summarized as follows: 1. For repetitive transactions, all the work of parsing, name binding, and access path selection is done once at precompilation time and need not be repeated. 2. Ad hoc queries are compiled on line into small machine-language routines that execute more efficiently than an interpreter. 3. Users are given a single language, SQL, for use in ad hoc queries as well as in writing PL/I and COBOL transaction programs. 4. The SQL parser, access path selection routines, and machine language code generator are used in common between query processing and precompilation of transaction programs. 5. When an index used by a transaction program is dropped, a new access path is automatically selected for the transaction without user intervention.

We have described the architecture of System R, including the Relational Data System and the Research Storage System. The RDS supports a flexible spectrum of binding times, ranging from precompilmion of “canned transactions” to on-line execution of ad hoc queries. The advantages of this approach may be summarized as follows: 1. For repetitive transactions, all the work of parsing, name binding, and access path selection is done once at precompilation time and need not be repeated. 2. Ad hoc queries are compiled on line into small machine-language routines that execute more efficiently than an interpreter. 3. Users are given a single language, SQL, for use in ad hoc queries as well as in writing PL/I and COBOL transaction programs. 4. The SQL parser, access path selection routines, and machine language code generator are used in common between query processing and precompilation of transaction programs. 5. When an index used by a transaction program is dropped, a new access path is automatically selected for the transaction without user intervention.

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Counts of unique values are frequently needed information in database systems. Especially, they are essential in query optimization and physical database design. Traditionally, exact counts were obtained by sorting, which is an expensive operation. In this paper we present three algorithms for counting unique values by probabilistic methods. These algorithms require only one pass over the data, and produce approximations to the true count with certain standard deviations. For deviations acceptable in practical environments (~10%), the algorithms require only modest amounts of memory space and computation time. We have implemented all three algorithms in System R. We also present the results of the experiments on accuracy and performance of these algorithms.

System R, an experimental database system, was constructed to demonstrate that the usability advantages of the relational data model can be realized in a system with the complete function and high performance required for everyday production use. This paper describes the three principal phases of the System R project and discusses some of the lessons learned from System R about the design of relational systems and database systems in general.

System R supports a high-level relational user language called SQL which may be used by ad hoc users at terminals or as an embedded data sublanguage in PL/I or COBOL. Host-language programs with embedded SQL statements are processed by the System R precompiler which replaces the SQL statements by calls to a machine-language access module. The precompilation approach removes much of the work of parsing, name binding, and access path selection from the path of a running program, enabling highly efficient support for repetitive transactions. Ad hoc queries are processed by a similar approach of name binding and access path selection which takes place on-line when the query is specified. By providing a flexible spectrum of binding times, System R permits transaction-oriented programs and ad hoc query users to share a database without loss of efficiency. System R is an experimental database management system designed and built by members of the IBM San Jose Research Laboratory as part of a research program on the relational model of data. This paper describes the architecture of System R, and gives some preliminary measurements of system performance in both the ad hoc query and the “canned program” environments.

A relational approach makes this experimental data base management system unusually easy to install and use. Some of the decisions made in System R design in order to enhance usability also offer major bonuses in other areas.

In a high level query and data manipulation language such as SQL, requests are stated non-procedurally, without reference to access paths. This paper describes how System R chooses access paths for both simple (single relation) and complex queries (such as joins), given a user specification of desired data as a boolean expression of predicates. System R is an experimental database management system developed to carry out research on the relational model of data. System R was designed and built by members of the IBM San Jose Research Laboratory.