FIX - WCPS needs subset pushdown for binary operators

[Bang Pham Huu]

For example there are 2 3D coverages:

• test_3d with plev irregular axis with coefficients: [0, 10, 50]
• test_3d_again with plev irregular axis with coefficients: [0, 50]

Now, with this WCPS query:

for $c in (test_3d),
    $d in (test_3d_again)

return encode( ($c + $d) [plev(50)], "png")

This query will return rasql query:

SELECT (c + d)[2] from test_3d AS c, test_3d_again AS d

because the output coverage of the binary operator c + d is c.
Then, the subset plev(50) will be applied to c.

However, this is an error in rasql, because, d[2] doesn't exist.

Hence, the correct way is WCPS needs to push down subset to each operand in the binary operator + in the WCPS query tree.

So the WCPS query (for illustration purpose) should be:

for $c in (test_3d),
    $d in (test_3d_again)

return encode( ($c[plev(50)] + $d[plev(50)]), "png")

[Bang Pham Huu]

worked already