Abstract: Techniques are provided for implementing an in-memory columnar data store that is configured to either grow or shrink in response to performance prediction data generated from database workload information. A system maintains allocations of volatile memory from a given memory area for a plurality of memory-consuming components in a database system. The system receives for each memory-consuming component, performance prediction data that contains performance predictions for a plurality of memory allocation sizes for the memory-consuming components. The system determines a target memory allocation for an in-memory columnar data store based on the performance predictions. The system determines an incrementally adjusted amount of memory for the in-memory columnar data store and causes the incrementally adjusted amount to be allocated to the in-memory columnar data store.

Abstract: Techniques are described for leveraging column dictionaries of tables for join, group-by and expression evaluation operations. In an embodiment, a table is stored in one or more data units, each data unit's metadata containing dictionaries for stored columns. Rather than storing unencoded column values, the data units may store columns as column vectors of dictionary-encoded values, in an embodiment. When performing a join operation, a matching of values may be performed on the build-side table using the unencoded, unencoded, values stored in the join-key dictionary(s) of the probe-side table, thus, significantly reducing the number of searching and matching operations. In an embodiment, a group-by operation may be executed by performing partial aggregations based on unique group-by key values as stored in the one or more group-by key dictionaries.

Abstract: Techniques related to cache storage formats are disclosed. In some embodiments, a set of values is stored in a cache as a set of first representations and a set of second representations. For example, the set of first representations may be a set of hardware-level representations, and the set of second representations may be a set of non-hardware-level representations. Responsive to receiving a query to be executed over the set of values, a determination is made as to whether or not it would be more efficient to execute the query over the set of first representations than to execute the query over the set of second representations. If the determination indicates that it would be more efficient to execute the query over the set of first representations than to execute the query over the set of second representations, the query is executed over the set of first representations.

Abstract: Techniques are described for leveraging column dictionaries of tables for join, group-by and expression evaluation operations. In an embodiment, a table is stored in one or more data units, each data unit's metadata containing dictionaries for stored columns. Rather than storing unencoded column values, the data units may store columns as column vectors of dictionary-encoded values, in an embodiment. When performing a join operation, a matching of values may be performed on the build-side table using the unencoded, unencoded, values stored in the join-key dictionary(s) of the probe-side table, thus, significantly reducing the number of searching and matching operations. In an embodiment, a group-by operation may be executed by performing partial aggregations based on unique group-by key values as stored in the one or more group-by key dictionaries.

Abstract: An automated method to align column values to proper byte boundaries for rapid scanning in a parallel processing database system. A table definition is received having a logical order of fields. The fields are re-ordered to create a physical order of fields. The physical order of fields has fixed length fields having a same byte alignment requirement positioned adjacent to each other in descending order from largest size to smallest size, and wherein a first fixed length field in the physical order is aligned on a proper byte boundary. Other embodiments, aspects and features are also disclosed.

Abstract: An automated method to align column values to proper byte boundaries for rapid scanning in a parallel processing database system. A table definition is received having a logical order of fields. The fields are re-ordered to create a physical order of fields. The physical order of fields has fixed length fields having a same byte alignment requirement positioned adjacent to each other in descending order from largest size to smallest size, and wherein a first fixed length field in the physical order is aligned on a proper byte boundary. Other embodiments, aspects and features are also disclosed.