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