diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/backend/executor/execExpr.c | 12 |
1 files changed, 9 insertions, 3 deletions
diff --git a/src/backend/executor/execExpr.c b/src/backend/executor/execExpr.c index a298b92af8c..d1c2bbbd44a 100644 --- a/src/backend/executor/execExpr.c +++ b/src/backend/executor/execExpr.c @@ -2443,14 +2443,14 @@ ExecInitArrayRef(ExprEvalStep *scratch, ArrayRef *aref, PlanState *parent, * refassgnexpr is itself a FieldStore or 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 CaseTextExpr mechanism. It's safe + * array and pass it down via the CaseTestExpr mechanism. It's safe * to reuse the CASE mechanism because there cannot be a CASE between * here and where the value would be needed, and an array assignment * can't be within a CASE either. (So saving and restoring * innermost_caseval is just paranoia, but let's do it anyway.) * * Since fetching the old element might be a nontrivial expense, do it - * only if the argument appears to actually need it. + * only if the argument actually needs it. */ if (isAssignmentIndirectionExpr(aref->refassgnexpr)) { @@ -2506,10 +2506,16 @@ ExecInitArrayRef(ExprEvalStep *scratch, ArrayRef *aref, PlanState *parent, /* * Helper for preparing ArrayRef expressions for evaluation: is expr a nested - * FieldStore or ArrayRef that might need the old element value passed down? + * FieldStore or ArrayRef that needs the old element value passed down? * * (We could use this in FieldStore too, but in that case passing the old * value is so cheap there's no need.) + * + * Note: it might seem that this needs to recurse, but it does not; the + * CaseTestExpr, if any, will be directly the arg or refexpr of the top-level + * node. Nested-assignment situations give rise to expression trees in which + * each level of assignment has its own CaseTestExpr, and the recursive + * structure appears within the newvals or refassgnexpr field. */ static bool isAssignmentIndirectionExpr(Expr *expr) |