Abstract: Methods, systems, and apparatus, including computer programs encoded on computer storage media, for a distributed parallel processing database system that persists table data in memory to a distributed file system. A distributed parallel processing database system persists table data in memory to a distributed file system. A parameter of creating a database table specifies that data records in the database table and history of changes to the data records can be stored in memory as well as in the distributed file system. When the database table is populated or otherwise modified, data records and the history in memory are evicted to the distributed file system as log files and removed from memory. The log files can be designated as write-only, where the data records, once written, cannot be read by structured query language (SQL) queries, or as read-write, where the data records, once written, can be read by SQL queries.

Abstract: Methods, systems, and apparatus for obtaining one or more metadata files, determining, by one or more computers and in accordance with a minor compaction setting, to perform a minor compaction of the one or more metadata files, creating one or more intermediate metadata files that each include at least compacted contacts of one or more of the metadata files, according to the determination to perform minor compaction of the one or more metadata files, determining, in accordance with a major compaction setting, to perform a major compaction of one or more of the intermediate metadata files, and creating one or more snapshot metadata files that each include at least compacted contents of one or more of the intermediate metadata files, according to the determination to perform the major compaction of one or more of the intermediate metadata files.

Abstract: Methods, systems, and apparatus, including computer programs encoded on computer storage media, for distributed data management. One of the methods includes maintaining, by a first member in a distributed data management system having multiple computing members installed on multiple respective computers, a first garbage collection version vector that includes, for each member in the distributed data management system, a garbage collection version that represents a number of garbage collection processes performed by the member on a respective copy of a replicated data region maintained by the member in the data management system. If the first garbage collection version vector is different than a second garbage collection version vector received from a different provider member, a first replication process is performed that is different than a second replication process that is performed when the first garbage collection version vector matches the second garbage collection version vector.

Abstract: Methods, systems, and apparatus for obtaining one or more metadata files, determining, by one or more computers and in accordance with a minor compaction setting, to perform a minor compaction of the one or more metadata files, creating one or more intermediate metadata files that each include at least compacted contacts of one or more of the metadata files, according to the determination to perform minor compaction of the one or more metadata files, determining, in accordance with a major compaction setting, to perform a major compaction of one or more of the intermediate metadata files, and creating one or more snapshot metadata files that each include at least compacted contents of one or more of the intermediate metadata files, according to the determination to perform the major compaction of one or more of the intermediate metadata files.

Abstract: Methods, systems, and apparatus for identifying two or more files, each of which include multiple entries, determining a respective size of each of the files, each size being an estimate of how many distinct entries exist in the respective file that are not garbage entries, determining a combined size of the files, where the combined size of the files is an arithmetic sum of the respective sizes of the files, estimating a compacted size of the files, where the estimated compacted size of the files is an estimate of how many distinct entries exist in the files that are not garbage entries, selecting the two or more files for compaction, based at least on a comparison of the combined size of the files to the estimated compacted size of the files, and compacting the two or more selected files.

Abstract: Methods, systems, and apparatus, including computer programs encoded on computer storage media, for a distributed parallel processing database system that persists table data in memory to a distributed file system. A distributed parallel processing database system persists table data in memory to a distributed file system. A parameter of creating a database table specifies that data records in the database table and history of changes to the data records can be stored in memory as well as in the distributed file system. When the database table is populated or otherwise modified, data records and the history in memory are evicted to the distributed file system as log files and removed from memory. The log files can be designated as write-only, where the data records, once written, cannot be read by structured query language (SQL) queries, or as read-write, where the data records, once written, can be read by SQL queries.

Abstract: Methods, systems, and apparatus for obtaining one or more metadata files, determining, by one or more computers and in accordance with a minor compaction setting, to perform a minor compaction of the one or more metadata files, creating one or more intermediate metadata files that each include at least compacted contacts of one or more of the metadata files, according to the determination to perform minor compaction of the one or more metadata files, determining, in accordance with a major compaction setting, to perform a major compaction of one or more of the intermediate metadata files, and creating one or more snapshot metadata files that each include at least compacted contents of one or more of the intermediate metadata files, according to the determination to perform the major compaction of one or more of the intermediate metadata files.

Abstract: A computer-implemented method for selecting file-recall modes based on environmental properties may include (1) intercepting a request to recall a file from a secondary storage system to a primary storage system, (2) identifying a value of a dynamic environmental property associated with the file that may negatively impact performance of a mode of recalling the file from the secondary storage system to the primary storage system, (3) identifying a policy that comprises criteria for selecting an appropriate recall mode for recalling the file from the secondary storage system to the primary storage system, (4) adaptively selecting, by applying the policy to the value of the dynamic environmental property, a recall mode for recalling the file, and (5) recalling the file from the secondary storage system to the primary storage system using the selected recall mode. Various additional methods, systems, and configured computer-readable-storage media are also disclosed.

Abstract: Methods, systems, and apparatus for identifying two or more files, each of which include multiple entries, determining a respective size of each of the files, each size being an estimate of how many distinct entries exist in the respective file that are not garbage entries, determining a combined size of the files, where the combined size of the files is an arithmetic sum of the respective sizes of the files, estimating a compacted size of the files, where the estimated compacted size of the files is an estimate of how many distinct entries exist in the files that are not garbage entries, selecting the two or more files for compaction, based at least on a comparison of the combined size of the files to the estimated compacted size of the files, and compacting the two or more selected files.

Abstract: Methods, systems, and apparatus for obtaining one or more metadata files, determining, by one or more computers and in accordance with a minor compaction setting, to perform a minor compaction of the one or more metadata files, creating one or more intermediate metadata files that each include at least compacted contacts of one or more of the metadata files, according to the determination to perform minor compaction of the one or more metadata files, determining, in accordance with a major compaction setting, to perform a major compaction of one or more of the intermediate metadata files, and creating one or more snapshot metadata files that each include at least compacted contents of one or more of the intermediate metadata files, according to the determination to perform the major compaction of one or more of the intermediate metadata files.

Abstract: A computer-implemented method for selecting file-recall modes based on environmental properties may include: 1) identifying a request to recall a file from a secondary storage system to a primary storage system, 2) identifying at least one environmental property associated with the file, 3) selecting, based at least in part on the identified environmental property, a recall mode for recalling the file, and then 4) recalling the file from the secondary storage system to the primary storage system using the selected recall mode. Various additional methods, systems, and configured computer-readable-storage media are also disclosed.