Ok, here is a workaround [though I suspect that performance is going to degrade (with respect to CHAR column for example[1]) because BUNtail is being called for each row...] sql_column *col = mvc_bind_column(m, tbl, colname[icol]); BAT *b = table_funcs.full_column(m->session->tr, col); //read the entire column into continuous memory on the tail heap of the BAT b BATiter *iterators = NULL; blob *blob_record; int ib; iterators = GDKzalloc(sizeof(BATiter)); iterators[0] = bat_iterator(b); // blob column iterator for (irow=0; irow < nrow; irow++) { blob_record = (blob*) BUNtail(iterators[0], irow); for (ib=0; ib < blob_record->nitems; ib++) { printf("blob data = %c, %02x\n", blob_record->data[ib], blob_record->data[ib]); } } p.s. [1] //For CHAR column it would look like this: sql_column *col = mvc_bind_column(m, tbl, colname[icol]); BAT *b = table_funcs.full_column(m->session->tr, col); //read the entire column into continuous memory on the tail heap of the BAT b char *tvbase, *cptr; unsigned char *readucrows; tvbase = (char *) b->T.vheap->base + GDK_VAROFFSET; readucrows = (unsigned char *) b->T.heap.base; for (irow=0; irow < nrow; irow++) { cptr = tvbase + *readucrows++; } Anton On Fri, Nov 10, 2017 at 4:13 PM, Anton Kravchenko < kravchenko.anton86@gmail.com> wrote:

I wonder how one would read BLOB column and loop over its rows?

BAT *b = table_funcs.full_column(m->session->tr, blob_col_name); //blob *readblobrows = (blob*) b->T.heap.base; //unsigned char *readblobrows = (unsigned char*) b->T.heap.base;

p.s. For INT column it would be go like this: int * readintrows = (int *) b->T.heap.base; for (irow=0; irow < nrow; irow++) { intvalue = *readintrows++; }

Thanks, Anton