Fix assorted fallout from IS [NOT] NULL patch.

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>

diff --git a/contrib/postgres_fdw/deparse.c b/contrib/postgres_fdw/deparse.c
index 8f09cd51ca89457b6977d0a1f07b3ec3f7761a35..dd25699d83f4b61d38c6eda314de8a5059423b3c 100644 (file)
--- a/contrib/postgres_fdw/deparse.c
+++ b/contrib/postgres_fdw/deparse.c
@@ -1806,10 +1806,27 @@ deparseNullTest(NullTest *node, deparse_expr_cxt *context)
 
    appendStringInfoChar(buf, '(');
    deparseExpr(node->arg, context);
-   if (node->nulltesttype == IS_NULL)
-       appendStringInfoString(buf, " IS NULL)");
+
+   /*
+    * For scalar inputs, we prefer to print as IS [NOT] NULL, which is
+    * shorter and traditional.  If it's a rowtype input but we're applying a
+    * scalar test, must print IS [NOT] DISTINCT FROM NULL to be semantically
+    * correct.
+    */
+   if (node->argisrow || !type_is_rowtype(exprType((Node *) node->arg)))
+   {
+       if (node->nulltesttype == IS_NULL)
+           appendStringInfoString(buf, " IS NULL)");
+       else
+           appendStringInfoString(buf, " IS NOT NULL)");
+   }
    else
-       appendStringInfoString(buf, " IS NOT NULL)");
+   {
+       if (node->nulltesttype == IS_NULL)
+           appendStringInfoString(buf, " IS NOT DISTINCT FROM NULL)");
+       else
+           appendStringInfoString(buf, " IS DISTINCT FROM NULL)");
+   }
 }
 
 /*

diff --git a/src/backend/optimizer/util/plancat.c b/src/backend/optimizer/util/plancat.c
index 2be0793cc0aaa57715c18710c24760a61aabbc0c..f037f90d9852e6ac14600b7ee9ac87a456d06a5a 100644 (file)
--- a/src/backend/optimizer/util/plancat.c
+++ b/src/backend/optimizer/util/plancat.c
@@ -1090,7 +1090,13 @@ get_relation_constraints(PlannerInfo *root,
                                                  att->attcollation,
                                                  0);
                    ntest->nulltesttype = IS_NOT_NULL;
-                   ntest->argisrow = type_is_rowtype(att->atttypid);
+
+                   /*
+                    * argisrow=false is correct even for a composite column,
+                    * because attnotnull does not represent a SQL-spec IS NOT
+                    * NULL test in such a case, just IS DISTINCT FROM NULL.
+                    */
+                   ntest->argisrow = false;
                    ntest->location = -1;
                    result = lappend(result, ntest);
                }

diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 97bdccf6ec6f60929adda0716375b73bba422fc7..8a6d0ad9661565b27550b9662e24f6e0b1a2a209 100644 (file)
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -7890,17 +7890,43 @@ get_rule_expr(Node *node, deparse_context *context,
                if (!PRETTY_PAREN(context))
                    appendStringInfoChar(buf, '(');
                get_rule_expr_paren((Node *) ntest->arg, context, true, node);
-               switch (ntest->nulltesttype)
+
+               /*
+                * For scalar inputs, we prefer to print as IS [NOT] NULL,
+                * which is shorter and traditional.  If it's a rowtype input
+                * but we're applying a scalar test, must print IS [NOT]
+                * DISTINCT FROM NULL to be semantically correct.
+                */
+               if (ntest->argisrow ||
+                   !type_is_rowtype(exprType((Node *) ntest->arg)))
                {
-                   case IS_NULL:
-                       appendStringInfoString(buf, " IS NULL");
-                       break;
-                   case IS_NOT_NULL:
-                       appendStringInfoString(buf, " IS NOT NULL");
-                       break;
-                   default:
-                       elog(ERROR, "unrecognized nulltesttype: %d",
-                            (int) ntest->nulltesttype);
+                   switch (ntest->nulltesttype)
+                   {
+                       case IS_NULL:
+                           appendStringInfoString(buf, " IS NULL");
+                           break;
+                       case IS_NOT_NULL:
+                           appendStringInfoString(buf, " IS NOT NULL");
+                           break;
+                       default:
+                           elog(ERROR, "unrecognized nulltesttype: %d",
+                                (int) ntest->nulltesttype);
+                   }
+               }
+               else
+               {
+                   switch (ntest->nulltesttype)
+                   {
+                       case IS_NULL:
+                           appendStringInfoString(buf, " IS NOT DISTINCT FROM NULL");
+                           break;
+                       case IS_NOT_NULL:
+                           appendStringInfoString(buf, " IS DISTINCT FROM NULL");
+                           break;
+                       default:
+                           elog(ERROR, "unrecognized nulltesttype: %d",
+                                (int) ntest->nulltesttype);
+                   }
                }
                if (!PRETTY_PAREN(context))
                    appendStringInfoChar(buf, ')');

diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index c8b1f907a8f5095ce4d19ecf640a75d500bd8840..a8a2c4e4e763cbbe268f40bedf1d1a297fa99dba 100644 (file)
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -1076,8 +1076,16 @@ typedef struct XmlExpr
  * NullTest represents the operation of testing a value for NULLness.
  * The appropriate test is performed and returned as a boolean Datum.
  *
- * NOTE: the semantics of this for rowtype inputs are noticeably different
- * from the scalar case.  We provide an "argisrow" flag to reflect that.
+ * When argisrow is false, this simply represents a test for the null value.
+ *
+ * When argisrow is true, the input expression must yield a rowtype, and
+ * the node implements "row IS [NOT] NULL" per the SQL standard.  This
+ * includes checking individual fields for NULLness when the row datum
+ * itself isn't NULL.
+ *
+ * NOTE: the combination of a rowtype input and argisrow==false does NOT
+ * correspond to the SQL notation "row IS [NOT] NULL"; instead, this case
+ * represents the SQL notation "row IS [NOT] DISTINCT FROM NULL".
  * ----------------
  */
 
@@ -1091,7 +1099,7 @@ typedef struct NullTest
    Expr        xpr;
    Expr       *arg;            /* input expression */
    NullTestType nulltesttype;  /* IS NULL, IS NOT NULL */
-   bool        argisrow;       /* T if input is of a composite type */
+   bool        argisrow;       /* T to perform field-by-field null checks */
    int         location;       /* token location, or -1 if unknown */
 } NullTest;
 

diff --git a/src/test/regress/expected/rowtypes.out b/src/test/regress/expected/rowtypes.out
index 2971640b4bd28b1cfccc2111b8232e526773ccb8..25b08281c85b781c6176a81caf5e6055aa1f6532 100644 (file)
--- a/src/test/regress/expected/rowtypes.out
+++ b/src/test/regress/expected/rowtypes.out
@@ -664,10 +664,10 @@ explain (verbose, costs off)
 select r, r is null as isnull, r is not null as isnotnull
 from (values (1,row(1,2)), (1,row(null,null)), (1,null),
              (null,row(1,2)), (null,row(null,null)), (null,null) ) r(a,b);
-                                                                                           QUERY PLAN                                                                                            
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+                                                                                                         QUERY PLAN                                                                                                          
+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  Values Scan on "*VALUES*"
-   Output: ROW("*VALUES*".column1, "*VALUES*".column2), (("*VALUES*".column1 IS NULL) AND ("*VALUES*".column2 IS NULL)), (("*VALUES*".column1 IS NOT NULL) AND ("*VALUES*".column2 IS NOT NULL))
+   Output: ROW("*VALUES*".column1, "*VALUES*".column2), (("*VALUES*".column1 IS NULL) AND ("*VALUES*".column2 IS NOT DISTINCT FROM NULL)), (("*VALUES*".column1 IS NOT NULL) AND ("*VALUES*".column2 IS DISTINCT FROM NULL))
 (2 rows)
 
 select r, r is null as isnull, r is not null as isnotnull