Abstract: A system and method of determining uniqueness properties of an expression. A root of the expression is first determined, where the root is one of a base relation, a unary operation or a binary operation. Once the root is determined, a first procedure of an augmented unique process is called to determine uniqueness properties of a child of that root. The procedure called is chosen based on the determined root. Where the root is a base relation, a first procedure of a uniqueness process is applied to determine the uniqueness properties of the base relation. Where the root is a unary or binary operation, the called procedure is suspended, a second procedure of the augmented unique process is called to determine the uniqueness properties of the child of the operation, and this process is repeated until a base relation is reached. Once a base relation is reached, the first procedure of the uniqueness process is applied to determine the uniqueness properties of the reached base relation.

Abstract: A system and method of determining uniqueness properties of an expression. A root of the expression is first determined, where the root is one of a base relation, a unary operation or a binary operation. Once the root is determined, a first procedure of an augmented unique process is called to determine uniqueness properties of a child of that root. The procedure called is chosen based on the determined root. Where the root is a base relation, a first procedure of a uniqueness process is applied to determine the uniqueness properties of the base relation. Where the root is a unary or binary operation, the called procedure is suspended, a second procedure of the augmented unique process is called to determine the uniqueness properties of the child of the operation, and this process is repeated until a base relation is reached. Once a base relation is reached, the first procedure of the uniqueness process is applied to determine the uniqueness properties of the reached base relation.

Abstract: A system and method of determining uniqueness properties of an expression. A root of the expression is first determined, where the root is one of a base relation, a unary operation or a binary operation. Once the root is determined, a first procedure of an augmented unique process is called to determine uniqueness properties of a child of that root. The procedure called is chosen based on the determined root. Where the root is a base relation, a first procedure of a uniqueness process is applied to determine the uniqueness properties of the base relation. Where the root is a unary or binary operation, the called procedure is suspended, a second procedure of the augmented unique process is called to determine the uniqueness properties of the child of the operation, and this process is repeated until a base relation is reached. Once a base relation is reached, the first procedure of the uniqueness process is applied to determine the uniqueness properties of the reached base relation.

Abstract: The present invention provides a system and method for the dictionary ordering of keys after expansion, compression and concatenation of their key parts. After each key part has been expanded through padding, each substring of identical characters of length greater than or equal to three is compressed through run-length encoding algorithm. The substring is replaced by the sequence character, a compression identifying character and a number identifying the number of characters being replaced. After compression and the subsequent concatenation, the keys are compared character by character. At the first instance of a miscomparison, the comparison scheme performs a normal dictionary ordering if neither of the characters are part of a compression sequence. If a character at the point of miscomparison is part of a compression sequence then an ordering decision is made based on the compression character, the length of the compressed substring and the character following the compressed substring.

Abstract: The present invention provides a system and method for the dictionary ordering of keys after expansion, compression and concatenation of their key parts. After each key part has been expanded through padding, each substring of identical characters of length greater than or equal to three is compressed through run-length encoding algorithm. The substring is replaced by the sequence character, a compression identifying character and a number identifying the number of characters being replaced. After compression and the subsequent concatenation, the keys are compared character by character. At the first instance of a miscomparison, the comparison scheme performs a normal dictionary ordering if neither of the characters are part of a compression sequence. If a character at the point of miscomparison is part of a compression sequence then an ordering decision is made based on the compression character, the length of the compressed substring and the character following the compressed substring.

Abstract: A computer program product, such as a pre-recorded software program on a floppy disk, is disclosed, for use with a processing and database system for off-loading, to disk controller, the extraction of committed data. Responsive to the pre-recorded program instructions, the system first picks a Commit.sub.-- LSN value and insures all the data modified prior to the Commit.sub.-- LSN value is processed following the DBMS policy of reducing some disk I/Os or not for the modified pages cached in the system. If the policy is not to do disk I/Os for such pages, then the system places the identifiers of those pages in an ignore list. Otherwise, the system writes those pages to disk and empties the ignore list. Afterwards, the system forwards the ignore list and the Commit.sub.-- LSN along with information regarding the data to be processed to the controller.

Abstract: A system for creating a static data compression dictionary adapted to a hardware-based data compression architecture. A static Ziv-Lempel dictionary is created and stored in memory for use in compressing database records. No data compression occurs during dictionary construction. A fixed-size Ziv-Lempel parse-tree is adapted to database characteristics in one of two alternate ways. First, the parse-tree is overbuilt substantially and then pruned back to a static size by eliminating the least recently used (LRU) nodes having the lowest use count. Alternatively, the parse-tree is built to a static size and thereafter selected nodes are replaced with new nodes upon database sampling. This node recycling procedure chooses the least-useful nodes for replacement according to a use count and LRU strategy while exhausting the database sample. The pruned Ziv-Lempel parse-tree is then transformed to a static dictionary configuration and stored in memory for use in a hardware-based database compression procedure.

Abstract: A method is disclosed for a database system for [off-loading] off-loading, to disk [controller] controller, the extraction of committed [data involving the] data. The system first [picking] picks a Commit.sub.-- LSN value and [insuring] insures all the data modified prior to the Commit.sub.-- LSN value is processed following the DBMS policy of reducing some disk I/Os or not for the modified pages cached in the system. If the policy is not to do disk I/Os for such [pages] pages, then the system places the identifiers of those pages in an ignore list. Otherwise, the system writes those pages to disk and empties the ignore list. [After which] Afterwards, the system forwards the ignore list and the Commit.sub.--LSN along with information regarding the data to be processed to the controller. The controller performs the off-load function by reading from disk every page identified by the system except those in the ignore [list] list, and [determining] determining, for each [page] page, if the page's Page.sub.

Abstract: Ziv-Lempel-type compression and expansion using separate static compression and expansion dictionaries as opposed to a single adaptive dictionary. The static dictionaries make random access processes usable for short data records instead of only long sequential data streams. Degree of compression and compression performance are improved by allowance of multiple extension characters per node and multiple children, of the same parent, that have the same first extension character. Performance is further improved by searching for matches on children of a parent and detecting a last possible match by means of fields in the parent instead of by accessing the children. Expansion performance is improved by representing in an entry not only the extension character or characters of the entry but also those of some number of ancestors of the entry, thus avoiding accessing the ancestors.

Abstract: Describes novel methods for compressing data character strings into "storage optimized indices" (SOIs) and stores their adaptive Ziv Lempel (AZL) indices, called "evolution based indices" (EBIs), in fields in corresponding entries in a SOI dictionary. The method also compresses data using the SOI dictionary, which accesses the corresponding EBIs for representing the compressed data. The EBIs are put into storage, or transmitted to a receiving location. Greater data compression processing efficiency is obtained by using the SOI dictionary than is available using prior types of AZL dictionaries. The disclosure further describes methods for decompressing EBI indices into corresponding phrases at a receiving location using either a conventional AZL dictionary or a SOI dictionary after translating received EBIs into SOIs. Also described is a submethod for phrase length determination for use in the decompression process.

Abstract: A system for creating a static data compression dictionary adapted to a hardware-based data compression architecture. A static Ziv-Lempel dictionary is created and stored in memory for use in compressing database records. No data compression occurs during dictionary construction. A fixed-size Ziv-Lempel parse-tree is adapted to database characteristics in one of two alternate ways. First, the parse-tree is overbuilt substantially and then pruned back to a static size by eliminating the least recently used (LRU) nodes having the lowest use count. Alternatively, the parse-tree is built to a static size and thereafter selected nodes are replaced with new nodes upon database sampling. This node recycling procedure chooses the least-useful nodes for replacement according to a use count and LRU strategy while exhausting the database sample. The pruned Ziv-Lempel parse-tree is then transformed to a static dictionary configuration and stored in memory for use in a hardware-based database compression procedure.

Abstract: A method and apparatus for avoiding line-accessed cache misses during a replacement/selection (tournament) sorting process. Prior to the sorting phase, the method includes the steps of sizing and writing maximal sets of sub-tree nodes of a nested ordering of keys, suitable for staging as cache lines. During the sort phase, the method includes the steps of prefetching into cache from CPU main memory one or more cache lines formed from a sub-tree of ancestor nodes immediate to the node in cache just selected for replacement. The combination of the clustering of ancestor nodes within individual cache lines and the prefetching of cache lines upon replacement node selection permits execution of the full tournament sort procedure without the normally-expected cache miss rate. For selection trees larger than those that can fit entirely into cache, the method avoids the second merge phase overhead that formerly doubled the sorting time necessary for larger cache sizes.

Abstract: A join optimization method is provided for use with a data processor for optimizing the processing of a query for retrieval of data from a relational computer database. The database is organized by relations and data is retrieved by preforming join operations on the relations. The join operations are optimized by randomly selecting an initial order for the join operations, assigning optimal join methods based on the initial order, finding an optimal order based on the assigned methods and repeating a polynomial number of times. The Krishanmurthy, Boral and Zaniolo (KBZ) Algorithm is used to determine a join optimization sequence and further refinement is provided by determining costs for alternate join order sequences using alternate join methods.

Abstract: A method of transmitting compressed data using a Ziv-Lempel compression/expansion algorithm, using an adaptive Ziv-Lempel (AZL) dictionary modified to a mature state. The mature state is signaled by a time to freeze signal sent as a switch-over signal from a transmitting location to each receiving location. These signals freeze and synchronize the AZL dictionaries at both locations, and starts a translation of the frozen AZL dictionary to a static SZL dictionary--at least at the transmitting location. The SZL dictionary is then used to compress records being transmitted. An index translation process is generates translation information to allow the receiving locations to decompress SZL indices into original characters. The AZL-to-SZL dictionary translation process re-organizes the frozen AZL to an SZL dictionary. The SZL process is used until either the end of the inputted sequence, or a time to unfreeze signal is generated.

Abstract: A method for data compression of records in storage that offers the decoding speed of Variable-to-Fixed codes without loss of sort order characteristics when stored in coded form. The methods include special treatment of the first ordered symbols in both source and decoder alphabets and do not depend on the use of prefix or arithmetic codes for their efficacy. The method saves database storage space by compressing actual records without loss of record sort order characteristics. The lexical ordering or "strong alphabetical" property of the encoding technique are left undisturbed by EOR codes and code-string terminations for byte-padding purposes because both EOR and code-string termination is accomplished with a zero-valued code word. This maintains record order through a proper magnitude relationship between the corresponding encoded records even if one record compresses to a different length than another.

Abstract: Results of a relational data base management system are joined in a process requiring, first, existence of an index on the join columns of the inner table, and, second, ordering on the join column of the first table. First, the index on the inner table's join column is scanned for rows of the inner table having join column values matching such values of rows in the outer table. This is done in a single pass through the outer table. Next, a temporary work table containing the identifiers of inner table rows having join column values matching those of the outer table is produced by concatenating the row identifiers to their matching outer table rows. Following this, the temporary work table is ordered by the identifiers. Last, the identifier list of inner table rows is used to retrieve the corresponding rows of the inner table.

Abstract: A multiprocessor system linked by a fiber optic ring network uses some of the bandwith of the ring network as a shared memory resource. Data slots are defined on the network which can carry message packets from one processor to another or network memory packets which circulate indefinitely on the network. One use of these network memory packets is as a lock management system for controlling concurrent access to a shared database by the multiple processors. The network memory packets are treated as lock entities. A processor indicates that it wants to procure a lock entity by circulating a packet, having a first network memory type, around the network. If no conflicting packets are detected when the circula ted packet returns, the type of the slot is changed to a second network memory type indicating a procured lock entity.

Abstract: Any number of sorted lists are efficiently partitioned into P lists, where P represents the number of processors available to sort the resulting lists. When given a large list to sort, the list is initially divided into P lists, and each processor sorts one of these lists. The lists are then exactly partitioned so that each of the elements in the new consecutive partitioned lists have values no smaller than any of the elements in the lists before it, nor larger than any of the elements in the list following it. Partitioning is done by P-1 processors. Each of the processors successively considers selected rows of elements from the sorted lists, and moves a partition boundary based on an element magnitude requirement and a partition size requirement. The new partitioned lists are then merged by the P processors, and simply strung together to provide a sorted list of all the elements.

Abstract: A multi-processor computer system in which each processor is under the control of separate system software and access a common database. A two level lock management system is used to prevent data corruption due to unsychronized data access by the multiple processors. By this system, subsets of data in the database are assigned respectively different lock entities. Before a task running on one of the processors access data in the database it first requests permission to access the data in a given mode with reference to the appropriate lock entity. A first level lock manager handles these requests synchronously, using a simplified model of the locking system having shared and exclusive lock modes to either grant or deny the request. All requests are then forwarded to a second level lock manager which grants or denies the request based on a more robust model of the locking system and queues denied requests.

Abstract: A modular fail-safe memory and an address generation mechanism that provides load balancing when the memory is shared by a number of processors. A plurality of memory modules are used for the memory with no specific limit on the number of memory modules, and a checksum block is used to back-up corresponding blocks in the other memory modules. The checksum blocks are distributed across the memory modules, and an address generation mechanism determines the checksum location for a specific memory block. This address generation mechanism ensures that checksum blocks are equally divided between the memory modules so that there is no memory bottleneck, is easy to implement in hardware, and is extended to provide similar properties when a module failure occurs.