Re: blobspaces

Mike Segel wrote: > > Sujit Pal wrote: > > > > Chao/Art > > > > > Hmmm, > Considering that a page is either 2 or 4K and if you are storing > blobs in table space, are they being stored with the row? Or > does the row have a pointer to an offset in a different chunk? > > I mean this may be a totally brain dead question, but, > how does Informix store a blob in "table" space? > Also, what happens when the data grows? What happens to the > organization of extents? > > It's been a while since I have looked at blobs so my alzhimers > is kicking in. The structure of the BLOB locator field in a row containing a tablespace blob column is the same as for a blobspace blob column, a 56byte structure including the pointer to the first blob page. A tablespace blob column which is smaller than a data page (2K or 4K) can coexist on a page with other small blobs or with the trailing piece of one or more larger blobs. Table space blob values longer than a page contain an 8byte pointer to the next piece which may itself be a full page or a trailer (ie the last piece and enough smaller than a page to share with other pieces). Tablespace blobs, like blobspace blobs are not updated their space is released, a new blob is allocated, and the locator in the data portion of the row is updated to point to the new blob. Art S. Kagel