Executing transactions on distributed databases

A distributed database system comprising:

• a query server;
• a distributed database including a plurality of data servers;
• and
• a non-transitory computer readable storage medium for storing instructions that when executed by a computer processor cause the computer processor to perform steps for exacting a transaction in the distributed database, the steps comprising:
• receiving, by a distributed database system comprising a query server and a plurality of data servers, a transaction comprising a plurality of statements, the plurality of statements comprising (1) a first modification statement, describing a first modification operation on a subset of records stored in the plurality of data servers, (2) a second modification statement, describing a second modification operation on the subset of records, and (3) a commit statement, indicating commit of the first and second modification operations;
• executing, at the query server, the transaction, the execution of the transaction comprising:
• receiving a copy of the subset of records from at least one of the plurality of data servers;
• and
• storing the copy of the subset of records at the query server;
• responsive to executing the first modification statement,
• performing the first modification operation on the subset of records stored locally at the query server to generate a first modified subset of records;
• and
• storing first modifications of the subset of records in a first delta table at the query server including difference between the first modified subset of records and original subset of records;
• and
• responsive to executing the second modification statement,
• performing the second modification operation on the first modified subset of records stored in the first delta table to generate a second modified subset of records;
• storing second modifications of the subset of records in a second delta table at the query server including difference between the second modified subset of records and the first modified subset of records;
• responsive to executing the commit statement, storing the second modified subset of records in a commit table at the query server;
• and
• responsive to completing execution of the transaction at the query server, causing the subset of records to be updated at the plurality of data servers based on the second modified subset of records in the commit table.

A non-transitory computer readable storage medium for storing instructions that when executed by a computer processor cause the computer processor to perform steps comprising:

• receiving, by a distributed database system comprising a query server and a plurality of data servers, a transaction comprising a plurality of statements, the plurality of statements comprising (1) a first modification statement, describing a first modification operation on a subset of records stored in the plurality of data servers, (2) a second modification statement, describing a second modification operation on the subset of records, and (3) a commit statement, indicating commit of the first and second modification operations;
• executing, at the query server, the transaction, the execution of the transaction comprising:
• receiving a copy of the subset of records from at least one of the plurality of data servers;
• and
• storing the copy of the subset of records at the query server;
• responsive to executing the first modification statement,
• performing the first modification operation on the subset of records stored locally at the query server to generate a first modified subset of records;
• and
• storing first modifications of the subset of records in a first delta table at the query server including difference between the first modified subset of records and original subset of records;
• and
• responsive to executing the second modification statement,
• performing the second modification operation on the first modified subset of records stored in the first delta table to generate a second modified subset of records;
• storing second modifications of the subset of records in a second delta table at the query server including difference between the second modified subset of records and the first modified subset of records;
• responsive to executing the commit statement, storing the second modified subset of records in a commit table at the query server;
• and
• responsive to completing execution of the transaction at the query server, causing the subset of records to be updated at the plurality of data servers based on the second modified subset of records in the commit table.