Multi-row transactions

A method for reading data from a cell of a database table as part of a particular transaction, the cell having a plurality of values, each value associated in the cell with a corresponding write timestamp value, the method comprising the steps of:

• obtaining a first timestamp value from a timestamp service;
• wherein the first timestamp value represents a start transaction timestamp of the particular transaction;
• reading a particular value of the plurality of values and the write timestamp value corresponding to the particular value from the cell;
• wherein the write timestamp value corresponding to the particular value represents a start transaction timestamp of another transaction that wrote the particular value to the cell;
• using the write timestamp value corresponding the particular value to read a second timestamp value from a transaction table;
• wherein the second timestamp value represents a commit timestamp of the other transaction that wrote the particular value to the cell;
• providing the particular value to a client application in response to determining, based on a comparison between the first timestamp value and the second timestamp value, that the other transaction that wrote the particular value to the cell committed before the particular transaction started;
• wherein the method is performed by one or more computing devices.

A non-transitory computer-readable medium storing instructions which, when executed by one or more computing devices, causes the one or more computing devices to perform a method for writing data to a plurality of database rows as part of a multi-row transaction, the method comprising the steps of:

• acquiring, from a lock service, a lock on a row of a transaction table;
• after acquiring the lock, writing the data to the plurality of database rows;
• after writing the data to the plurality of database rows, querying the lock service to determine whether the lock was in fact held by the lock service for the multi-row transaction since the lock was acquired from the lock service and while writing the data to the plurality of database rows;
• and
• adding the row to the transaction table in response to determining, based on the querying, that the lock was in fact held by the lock service for the multi-row transaction since the lock was acquired from the lock service and while writing the data to the plurality of database rows;
• wherein the method is performed by one or more computing devices.

A non-transitory computer-readable medium storing instructions which, when executed by one or more computing devices, causes the one or more computing devices to perform a method for reading data from a cell of a database table as part of a particular transaction, the cell having a plurality of values, each value associated in the cell with a corresponding write timestamp value, the method comprising the steps of:

• obtaining a first timestamp value from a timestamp service;
• wherein the first timestamp value represents a start transaction timestamp of the particular transaction;
• reading a particular value of the plurality of values and the write timestamp value corresponding to the particular value from the cell;
• wherein the write timestamp value corresponding to the particular value represents a start transaction timestamp of another transaction that wrote the particular value to the cell;
• using the write timestamp value corresponding the particular value to read a second timestamp value from a transaction table;
• wherein the second timestamp value represents a commit timestamp of the other transaction that wrote the particular value to the cell;
• providing the particular value to a client application in response to determining, based on a comparison between the first timestamp value and the second timestamp value, that the other transaction that wrote the particular value to the cell committed before the particular transaction started;
• wherein the method is performed by one or more computing devices.

A system comprising:

• a lock service;
• one or more processors;
• and
• one or more non-transitory computer-readable media storing instructions which, when executed by the one or more processors, cause the one or more processors to perform a method for writing data to a plurality of database rows as part of a multi-row transaction, the method comprising the steps of:
• acquiring, from the lock service, a lock on a row of a transaction table;
• after acquiring the lock, writing the data to the plurality of database rows;
• after writing the data to the plurality of database rows, querying the lock service to determine whether the lock was in fact held by the lock service for the multi-row transaction since the lock was acquired from the lock service and while writing the data to the plurality of database rows;
• and
• adding the row to the transaction table in response to determining, based on the querying, that the lock was in fact held by the lock service for the multi-row transaction since the lock was acquired from the lock service and while writing the data to the plurality of database rows.