1e2f96f0a5
Commits 4452000f3 et al established semantics for NullTest.argisrow that are a bit different from its initial conception: rather than being merely a cache of whether we've determined the input to have composite type, the flag now has the further meaning that we should apply field-by-field testing as per the standard's definition of IS [NOT] NULL. If argisrow is false and yet the input has composite type, the construct instead has the semantics of IS [NOT] DISTINCT FROM NULL. Update the comments in primnodes.h to clarify this, and fix ruleutils.c and deparse.c to print such cases correctly. In the case of ruleutils.c, this merely results in cosmetic changes in EXPLAIN output, since the case can't currently arise in stored rules. However, it represents a live bug for deparse.c, which would formerly have sent a remote query that had semantics different from the local behavior. (From the user's standpoint, this means that testing a remote nested-composite column for null-ness could have had unexpected recursive behavior much like that fixed in 4452000f3.) In a related but somewhat independent fix, make plancat.c set argisrow to false in all NullTest expressions constructed to represent "attnotnull" constructs. Since attnotnull is actually enforced as a simple null-value check, this is a more accurate representation of the semantics; we were previously overpromising what it meant for composite columns, which might possibly lead to incorrect planner optimizations. (It seems that what the SQL spec expects a NOT NULL constraint to mean is an IS NOT NULL test, so arguably we are violating the spec and should fix attnotnull to do the other thing. If we ever do, this part should get reverted.) Back-patch, same as the previous commit. Discussion: <10682.1469566308@sss.pgh.pa.us>
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