1. A computer program product comprising a computer program stored in a memory and executed by a processor to perform operations for generating a distributed text index for parallel query processing by a number of nodes, the operations of the computer program product comprising: generating a set of node indices for text indexing a set of documents, each node text index covering a subset of the documents; for each node text index: calculating a local frequency measure for each term of the node text index on the basis of a frequency of documents containing the term in the subset of the documents of the node; calculating a global frequency measure for each term on the basis of a frequency of documents containing the term in the set of documents; and calculating a quality measure for the node text index as a mean value of each difference for each term of the node of the local frequency measure of the term and the global frequency measure of the term, wherein the quality measure indicates a validity of the global frequency measure for each node text index.