Statistics collection using path-value pairs for relational databases

A system for collecting statistics associated with data in a database, the system comprising:

• a memory estimator for determining an amount of memory needed to collect statistics for data associated with a defined data type in a relational database, wherein the defined data type is based upon a mark-up language using a tree structure with one or more root-to-node paths therein;
• a memory allocator for allocating the amount of memory as determined for collecting the statistics for the data of the defined data type;
• and
• a statistics collector for performing a collection of statistics for the data of the defined data type in a single pass through the database and within the amount of memory which has been allocated and for at least determining a total number of instances of at least one path-identifier associated with a given value within a given set of documents.

A computer readable medium for collecting statistics associated with data in a database, the computer readable medium comprising instructions for:

• determining an amount of memory needed to collect statistics for data associated with a defined data type in a relational database, wherein the defined data type is based upon a mark-up language using a tree structure with one or more root-to-node paths therein;
• allocating the amount of memory as determined for collecting the statistics for the data of the defined data type;
• and
• performing a collection of statistics for the data of the defined data type in a single pass through the database and within the amount of memory which has been allocated, wherein the performing includes at least:
• determining a total number of instances of at least one path-identifier associated with a given value within a given set of documents.