Hi,
In the context of my expression evaluation patch, I was trying to
increase test coverage of execQual.c. I'm a bit confused about
$subject. ExecEvalArrayRef() has the following codepath:
if (isAssignment) { Datum sourceData; Datum save_datum; bool save_isNull;
/* * We might have a nested-assignment situation, in which the * refassgnexpr is itself a
FieldStoreor ArrayRef that needs to * obtain and modify the previous value of the array element or slice
*being replaced. If so, we have to extract that value from the * array and pass it down via the econtext's
caseValue. It's safe to * reuse the CASE mechanism because there cannot be a CASE between * here and
wherethe value would be needed, and an array assignment * can't be within a CASE either. (So saving and
restoringthe * caseValue is just paranoia, but let's do it anyway.) * * Since fetching the old
elementmight be a nontrivial expense, do it * only if the argument appears to actually need it. */
save_datum= econtext->caseValue_datum; save_isNull = econtext->caseValue_isNull;
if (isAssignmentIndirectionExpr(astate->refassgnexpr)) if (*isNull) { ...
} else if (lIndex == NULL) { ... } else {
econtext->caseValue_datum = array_get_slice(array_source, i,
upper.indx,lower.indx, upperProvided, lowerProvided,
astate->refattrlength, astate->refelemlength,
astate->refelembyval, astate->refelemalign); econtext->caseValue_isNull
=false; } }
...
That's support for multiple indirect assignments, assigning to array
slices. But I can't figure out how to reach that bit of code.
The !slice code can be reached:
CREATE TABLE arr(d int[]);
CREATE TABLE arr2(arr arr)
INSERT INTO arr2(arr[1].d, arr[2].d) VALUES(ARRAY[1,2],ARRAY[3,4]) RETURNING *
┌───────────────────────────────┐
│ arr │
├───────────────────────────────┤
│ {"(\"{1,2}\")","(\"{3,4}\")"} │
└───────────────────────────────┘
But I don't see how to the slice code can be reached. The indirection
code is only triggered when isAssignmentIndirectionExpr is true, which
requires that refassgnexpr is a FieldStore/ArrayRef containing a
CaseTest.
But that doesn't make sense for slices, because there can't be a
FieldStore directly below a slice (you'd get "subfield "d" is of type
integer[] but expression is of type integer" - makes sense), nor can
there be an ArrayRef inside a slice ArrayRef for assignemnts, because
there are no parens in the LHS, and consecutive []'s are collapsed into
a single ArrayRef.
Am I standing on my own foot here?
Greetings,
Andres Freund
