Techniques of efficient XML query using combination of XML table index and path/value index

A volatile or non-volatile computer-readable medium storing one or more sequences of instructions which, when executed by one or more processors, cause:

• executing an index generation statement identifying a plurality of path expressions and a plurality of columns of a first table for indexing a collection of documents wherein said plurality of path expressions identify less than all nodes in the collection of documents
• wherein for each column of said plurality of columns, said index generation statement specifies an association between said each column and a respective path expression of said plurality of path expressions;
• wherein execution of said index generation statement causes generation of said first table, wherein the first table comprises a first set of entries;
• wherein for each column of the plurality of columns of said first table, each entry of the first set of entries contains a node value of a node identified by the respective path expression of said each column, said node value being from a document of said collection of documents;
• wherein the collection of documents is also indexed by a second table, wherein the second table comprises a second set of entries, each entry in the second set of entries:
• being associated with a given node of a document in the collection of documents, and
• including location data for locating content in the document, wherein the content is associated with the given node and path data that corresponds to a path to the given node in the document;
• and
• intercepting, by a database system, a query for first information from a collection of documents,
• wherein the query for first information does not reference said first table and said second table;
• said database system rewriting the query for first information to generate a rewritten query that references said first table and said second table;
• wherein the query comprises one or more predicates;
• based on the rewritten query, said database system generating a first query plan using both the first table and the second table, wherein the first query plan, when executed by the database system, causes the database system to perform:
• identifying one or more first entries from the first table that contain a node value that satisfies the one or more predicates;
• extracting second information from the one or more first entries identified from the first table;
• extracting, using the second information, the first information from one or more second entries in the second table
• wherein the first table and the second table are two different tables.