Abstract: A system uses a hybrid key-value storage engine that uses log-structured merge tree and a segmented log-structured object store. The system performs garbage collection of stale document versions avoiding index lookup during log segment compaction. The system separates index and document data to minimize write amplification. The system maintains a delete list using a log-structured merge-tree to store stale document sequence numbers and corresponding sizes per log segment. For each log segment from the plurality of log segments, the system determines a measure of fragmentation of the log segment based on sizes of deleted documents of the log segment from the second log-structured merge-tree. If the fragmentation exceeds a threshold, the system initiates a compaction operation for the log segment.

Abstract: A system uses a hybrid key-value storage engine that uses log-structured merge tree and a segmented log-structured object store. The system performs garbage collection of stale document versions avoiding index lookup during log segment compaction. The system separates index and document data to minimize write amplification. The system maintains a delete list using a log-structured merge-tree to store stale document sequence numbers and corresponding sizes per log segment. For each log segment from the plurality of log segments, the system determines a measure of fragmentation of the log segment based on sizes of deleted documents of the log segment from the second log-structured merge-tree. If the fragmentation exceeds a threshold, the system initiates a compaction operation for the log segment.

Abstract: A document-oriented database system generates an optimal query execution plan for database queries on an untyped field included in a collection of documents. Each untyped field is configured to store one or more scalar data values. The system generates histograms for scalar data values stored in untyped fields. Responsive to receiving a query statement for fetching or updating data value stored in one of the untyped fields, the system assigns a cost to each operator associated with the query statement based on the histogram, compares the costs assigned to the operators, and generates a query execution plan based on the comparison, and query the database using the query execution plan.

Abstract: A system replicates data stored in a source database to target databases of systems such as mobile devices. The source database stores data objects, for example, documents, media objects, and so on. The source system ensures that the data objects stored in a target database correspond to a set of data objects that can be accessed by the user associated with the target database as determined by an access control specification of the user. Accordingly, if the access control specification of the user changes, the source system performs data synchronization to modify the set of data objects stored on the target database. If the access control specification is modified to revoke the user's access to a set of data objects, the source system performs data synchronization to send information identifying the set of data objects with a request to remove the data objects from the target database.

Abstract: A database system performs queries on fields storing arrays of a database (i.e., array fields) using de-duplication indexes. The system generates de-duplication indexes for array fields. The de-duplication indexes include unique entries for corresponding distinct values stored by the array fields. The system uses the de-duplication indexes to perform efficient queries specifying corresponding array fields. The system may further generate de-duplication indexes corresponding one or more fields storing various types of values. In various embodiments, the system selects an optimal index from various indexes usable to execute a query, such as a de-duplication index and a conventional index.

Abstract: A distributed database system receives and executes a transaction including a first modification statement describing a first modification operation on a subset of records, a second modification statement describing a second modification operation on the subset of records, and a commit statement. Responsive to executing the first and second modification statements, the system receives a copy of the subset of records from data servers; performs the first modification operation to generate a first modified subset of records; and performs the second modification operation on the first modified subset of records. Responsive to executing the commit statement, the system stores the second modified subset of records in a commit table and causes the subset of records to be updated at the data servers.

Abstract: A distributed database system executes transactions on a distributed database. A received transaction includes statements describing modifications of records stored in the distributed database. The distributed database system executes the transaction at a query server by obtaining copies of records corresponding to the statements of the transaction and performing the modifications specified by the statements of the transaction on the record copies. The distributed database system stores the modified record copies at the query server during execution of the transaction. After the transaction has successfully been executed at the query server, the distributed database system attempts to perform a commit process to update the records stored in the distributed database based on the modified record copies.

Abstract: A database system performs queries on fields storing arrays of a database (i.e., array fields) using de-duplication indexes. The system generates de-duplication indexes for array fields. The de-duplication indexes include unique entries for corresponding distinct values stored by the array fields. The system uses the de-duplication indexes to perform efficient queries specifying corresponding array fields. The system may further generate de-duplication indexes corresponding one or more fields storing various types of values. In various embodiments, the system selects an optimal index from various indexes usable to execute a query, such as a de-duplication index and a conventional index.

Abstract: A document-oriented database system generates an optimal query execution plan for database queries on an untyped data field included in a collection of documents. The system generates histograms for multiple types of data stored by the untyped data field and uses the histograms to assign costs to operators usable to execute the database query. The system generates the optimal query execution plan by selecting operators based on the assigned costs. In various embodiments, the untyped data field stores scalars, arrays, and objects.

Abstract: A document-oriented database system generates an optimal query execution plan for database queries on an untyped data field included in a collection of documents. The system generates histograms for multiple types of data stored by the untyped data field and uses the histograms to assign costs to operators usable to execute the database query. The system generates the optimal query execution plan by selecting operators based on the assigned costs. In various embodiments, the untyped data field stores scalars, arrays, and objects.