I am using MonetDB v11.27.9 on cent7.

1) 'select v_blob from blob_table' produces a virtual memory spike ~800Gb

[using a 'limit' reproduces virtual memory spike too]

From 'select * from storage()' it looks a blob column size is ~25Gb.

2) And 'create table new_blob_table as (select v_blob from blob_table) with data;'

produces only ~50Gb of virtual memory.

3) Also for a table with non-blob column both

'select * from nonblob_table'

and

'create new_nonblobtable as (select * from nonblob_table) with data;'

produce the ~same virtual memory consumption.

p.s. Here are steps to reproduce this issue

# to generate date by using Python

hex_blob='47'*2000

hex_blob_chunk=(hex_blob+'\n')*1000

f=open('blob_data.txt','w')

for irow in range(10000):

f.write(hex_blob_chunk)

f.close()

# to load data into Monet blob_table

create table blob_table(v_blob blob);

COPY 10000000 RECORDS INTO blob_table FROM '/home/blob_data.txt' using delimiters ',','\n' NULL AS '' LOCKED;

# to produce virtual memory spike of ~800GB

select * from blob_table limit 50000;

# to produce virtual memory of ~50Gb

create table new_blob_table as (select * from blob_table) with data;

Thanks,

Anton