1. A computerized searchable repository for documents, each document having a structured metadata part and one or more unstructured content parts, comprising: a storage device to store the documents, a full text index and a linking structure, the content parts of the documents being stored in a single-instanced manner to avoid storing duplication of identical content parts, the full text index being usable for keyword searching of the documents and including a metadata index and a content index of the metadata and content parts respectively of the documents, the linking structure including metadata-to-content links and content-to-metadata linking entries, each metadata-to-content link linking a metadata part of a respective document to each content part of the document, each content-to-metadata linking entry having one or more content-to-metadata links collectively linking a respective content part to the metadata parts of a group of documents that each include the content part; and a processor to perform full text indexing of the documents in the storage device, the full text indexing of each document including metadata indexing a metadata part, conditionally content indexing a content part, and updating the linking structure, the content indexing being performed only if the content part is a new content part not matching any of at least a set of content parts already stored in a content store and indexed in the content index, each of the metadata indexing and content indexing including generating new index entries in the metadata or content index respectively for the metadata or content part respectively, each index entry associating a respective key word or key value with a corresponding one or more metadata or content parts containing the key word or key value, and the updating of the linking structure including generating new metadata-to-content and content-to-metadata links between the metadata part and either the new content part or an existing matching content part if present.
2. A computerized searchable repository according to claim 1 , wherein the documents are organized into sets in the storage device, and wherein: the content index is a single content index including index entries for content parts of all the documents, and the metadata index includes a plurality of metadata indexes each including index entries for metadata parts of only a corresponding set of the documents; and the linking structure includes a single content-to-metadata linking structure containing the content-to-metadata entries for all the documents, and a plurality of metadata-to-content linking structures each containing the metadata-to-content links for only a corresponding set of the documents.