Abstract: Read-only nodes of a distributed database system may implement index structure navigation using page versions. A read request may be received at a read only node of a distributed database for select data. Data pages linked together to form an index structure for data stored for the distributed database may be navigated according to versions maintained for the data pages in order to identify one or more locations to access for the select data. One or more prior versions of data pages may be selected as part navigating the index structure according to a consistent view of the distributed database associated with the read request. Change notifications may also be received at the read-only node modifying the data pages of the index structure. The index structure modifications may be applied without blocking the index structure navigation for servicing the read request.

Abstract: A database system may include a database service and a separate distributed storage service. The database service (or a database engine head node thereof) may be responsible for query parsing, optimization, and execution, transactionality, and consistency, while the storage service may be responsible for generating data pages from redo log records and for durability of those data pages. For example, in response to a write request directed to a particular data page, the database engine head node may generate a redo log record and send it, but not the data page, to a storage service node. The storage service node may store the redo log record and return a write acknowledgement to the database service prior to applying the redo log record. The server node may apply the redo log record and other redo log records to a previously stored version of the data page to create a current version.

Abstract: A distributed database system may perform a single phase commit for transactions involving updates to multiple databases of the distributed database system. A client request may be received that involves updates to multiple database of the distributed database system. The updates may be performed at a front-end database and a back-end database. Log records indicating the updates to the front-end database may be sent to the back-end database. The log records and the updates performed at the back-end database may be committed together as a single phase commit at the back-end database. In the event of a system failure of the front-end database, log records may be requested and received from the back-end database. A restoration of the front-end database may be performed based, at least in part, on the received log records.

Abstract: A database system may maintain a plurality of log records at a distributed storage system. Each of the plurality of log records may be associated with a respective change to a data page. The plurality of log records may be transformed (e.g., cropped, prune, reduce, fused, deleted, merged, added, etc.).

Abstract: Self-describing data blocks of a minimum atomic write size may be stored for a data store. Data may be received for storage in a data block of a plurality of data blocks at a persistent storage device that are equivalent to a minimum atomic write size for the persistent storage device. Metadata may be generated for the data that includes an error detection code which is generated for the data and the metadata together. The data and the metadata are sent to the persistent storage to device to store together in the data block. An individual atomic write operation may write together the data and the metadata in the data block. When accessed, the error detection code is applicable to detect errors. The metadata may also be applicable to determine whether the data is stored for a currently assigned purpose or a previously assigned purpose of the data block.

Abstract: A distributed database system may implement log-structured distributed storage using a single log sequence number space. A log for a data volume may be maintained in a log-structured distributed storage system. The log may be segmented across multiple protection groups according to a partitioning of user data for the data volume. Updates to the log may be assigned a log sequence number from a log sequence number space for the data volume. A protection group may be determined for an update according to which partition of user data space the update pertains. Metadata to be included with the log record may indicate a previous log sequence number of a log record maintained at the protection group. The log record may be sent to the protection group and identified as committed based on acknowledgments received from storage nodes implementing the protection group.

Abstract: A distributed data warehouse system maintains data blocks on behalf of clients, and stores primary and secondary copies of data blocks on different disks or nodes in a cluster. The data warehouse system may back up data blocks in a key-value backup storage system. In response to a query targeting a data block previously stored in the cluster, the data warehouse system may determine whether a consistent, uncorrupted copy of the data block is available in the cluster (e.g., by applying a consistency check). If not (e.g., if a disk or node failed), the data warehouse system may automatically initiate an operation to restore the data block from the backup storage system, using a unique identifier of the data block to access a backup copy. The target data may be returned in a query response prior to restoring primary and secondary copies of the data block in the cluster.

Abstract: Data temporarily stored in volatile memory (e.g., RAM) on a host machine can be protected using a component such as an NV-DIMM, which includes components such as an ASIC, non-volatile memory, and a battery. If power is lost to the host, the battery provides the ASIC with the power needed to determine data in the volatile memory that is protected. This protected data then can be transferred to the non-volatile memory on the NV-DIMM. When power is restored, an application or other entity can contact the NV-DIMM to recover the data, which can be transferred over a sideband channel to be restored as appropriate for a prior operation. In at least some embodiments, the NV-DIMM can receive a key over the sideband channel that can be used to encrypt and decrypt the data for further security.

Abstract: A network-based services provider may reserve and provision primary resource instance capacity for a given service (e.g., enough compute instances, storage instances, or other virtual resource instances to implement the service) in one or more availability zones, and may designate contingency resource instance capacity for the service in another availability zone (without provisioning or reserving the contingency instances for the exclusive use of the service). For example, the service provider may provision resource instance(s) for a database engine head node in one availability zone and designate resource instance capacity for another database engine head node in another availability zone without instantiating the other database engine head node. While the service operates as expected using the primary resource instance capacity, the contingency resource capacity may be leased to other entities on a spot market. Leases for contingency instance capacity may be revoked when needed for the given service (e.g.

Abstract: Read-only nodes of a distributed database system may implement index structure navigation using page versions. A read request may be received at a read only node of a distributed database for select data. Data pages linked together to form an index structure for data stored for the distributed database may be navigated according to versions maintained for the data pages in order to identify one or more locations to access for the select data. One or more prior versions of data pages may be selected as part navigating the index structure according to a consistent view of the distributed database associated with the read request. Change notifications may also be received at the read-only node modifying the data pages of the index structure. The index structure modifications may be applied without blocking the index structure navigation for servicing the read request.

Abstract: A database system may include a database service and a separate distributed storage service. The database service (or a database engine head node thereof) may be responsible for query parsing, optimization, and execution, transactionality, and consistency, while the storage service may be responsible for generating data pages from redo log records and for durability of those data pages. For example, in response to a write request directed to a particular data page, the database engine head node may generate a redo log record and send it, but not the data page, to a storage service node. The storage service node may store the redo log record and return a write acknowledgement to the database service prior to applying the redo log record. The server node may apply the redo log record and other redo log records to a previously stored version of the data page to create a current version.

Abstract: A distributed database system may efficiently replicate distributed storage system changes on one or more read-only nodes. Storage metadata that indicates an access scheme for obtaining data for a particular view of the database from a distributed storage system may be maintained at a read-only node. An update to the storage metadata may be received that indicates a change to the distributed storage system that affects the validity of read requests for a different particular view of the database. In some embodiments, the change may indicate which storage nodes may be storing data according to the different particular view of the database, such as a change in membership of a protection group for the data at the distributed storage system. The storage metadata at the read-only node may be updated according to the received update such that a subsequent read request for the different particular view of the database is sent to the distributed storage system according to the updated access scheme.

Abstract: A database system may maintain a plurality of log records at a distributed storage system. Each of the plurality of log records may be associated with a respective change to a data page. The plurality of log records may be transformed (e.g., cropped, prune, reduce, fused, deleted, merged, added, etc.).

Abstract: Data may be efficiently analyzed and compressed as part of a data compression service. A data compression request may be received from a client indicating data to be compressed. An analysis of the data or metadata associated with the data may be performed. In at least some embodiments, this analysis may be a rules-based analysis. Some embodiments may employ one or more machine learning techniques to historical compression data to update the rules-based analysis. One or more compression techniques may be selected out of a plurality of compression techniques to be applied to the data. Data compression candidates may then be generated according to the selected compression techniques. In some embodiments, a compression service restriction may be enforced. One of the data compression candidates may be selected and sent in a response.

Abstract: Self-describing data blocks of a minimum atomic write size may be stored for a data store. Data may be received for storage in a data block of a plurality of data blocks at a persistent storage device that are equivalent to a minimum atomic write size for the persistent storage device. Metadata may be generated for the data that includes an error detection code which is generated for the data and the metadata together. The data and the metadata are sent to the persistent storage device to store together in the data block. An individual atomic write operation may write together the data and the metadata in the data block. When accessed, the error detection code is applicable to detect errors. The metadata may also be applicable to determine whether the data is stored for a currently assigned purpose or a previously assigned purpose of the data block.

Abstract: A distributed data warehouse system maintains data blocks on behalf of clients, and stores primary and secondary copies of data blocks on different disks or nodes in a cluster. The data warehouse system may back up data blocks in a key-value backup storage system. In response to a query targeting a data block previously stored in the cluster, the data warehouse system may determine whether a consistent, uncorrupted copy of the data block is available in the cluster (e.g., by applying a consistency check). If not (e.g., if a disk or node failed), the data warehouse system may automatically initiate an operation to restore the data block from the backup storage system, using a unique identifier of the data block to access a backup copy. The target data may be returned in a query response prior to restoring primary and secondary copies of the data block in the cluster.

Abstract: A distributed data warehouse system may maintain data blocks on behalf of clients in multiple clusters in a data store. Each cluster may include a single leader node and multiple compute nodes, each including multiple disks storing data. The warehouse system may store primary and secondary copies of each data block on different disks or nodes in a cluster. Each node may include a data structure that maintains metadata about each data block stored on the node, including its unique identifier. The warehouse system may back up data blocks in a remote key-value backup storage system with high durability. A streaming restore operation may be used to retrieve data blocks from backup storage using their unique identifiers as keys. The warehouse system may service incoming queries (and may satisfy some queries by retrieving data from backup storage on an as-needed basis) prior to completion of the restore operation.

Abstract: A distributed data warehouse system may maintain data blocks on behalf of clients, and may store primary and secondary copies of each data block on different disks or nodes in a cluster. The warehouse system may back up data blocks in a remote key-value backup storage system. A restore operation may retrieve data blocks from backup storage using their unique identifiers as keys (while incoming queries are serviced) in response to a failure or a query targeting data that was lost or corrupted. The order in which data blocks are restored may be dependent on the relative likelihood that they will be accessed in the near future (e.g., based on how recently or frequently they were accessed, written, or backed up; the values of one or more access counters associated with each data block; or how recently a database table containing data in each data block was loaded).

Abstract: A query optimizer may receive a query (e.g., from a source that generated the query). Input that specifies both a query hint string and a hint may be received to a hint specification interface. The hint may be applied to the query, from outside the query, to optimize a query execution plan. Applying the hint may be based, at least in part, on a query hint string. For example, which query block is associated with the query hint string may be determined. Upon such a determination, the hint may be applied to the determined query block.

Abstract: Data may be efficiently analyzed and compressed as part of a data compression service. A data compression request may be received from a client indicating data to be compressed. An analysis of the data or metadata associated with the data may be performed. In at least some embodiments, this analysis may be a rules-based analysis. Some embodiments may employ one or more machine learning techniques to historical compression data to update the rules-based analysis. One or more compression techniques may be selected out of a plurality of compression techniques to be applied to the data. Data compression candidates may then be generated according to the selected compression techniques. In some embodiments, a compression service restriction may be enforced. One of the data compression candidates may be selected and sent in a response.