Attempt to allocate too much space in UPDATE query

[eyalroz]

Consider the following query:

UPDATE table_3 AS t3
SET c1 = t2.c1
FROM table_1 AS t1, table_2 AS t2
WHERE false;

in the case that:

• Table 1 is small (3 records).
• Table 2 is large (~60 Million records).
• Table 3 is small (less than 1000 records).
• c1 is a column of type CHAR(3)

On my system, this gets me:

GDK reported error: GDKmmap: requested too much virtual memory; memory requested: 2307734896640, memory in use: 387076736, virtual memory in use: 2308246491776
HEAPalloc: Insufficient space for HEAP of 2307734835200 bytes.

Clearly, too much memory is being allocated (even if we ignore the fact that the condition is never met).

Software versions

• MonetDB 11.39.11
• Built from source
• Devuan GNU/Linux 3 Beowulf

[PedroTadim]

On default branch, we added optimizations for these trivial cases. You can try it there. It will be available on the next feature release.

[eyalroz]

@PedroTadim : You mean, the master branch here has it?

[yzchang]

yes, on github, it's the master branch