Fix type-checking of RECORD-returning functions in FROM.

In the corner case where a function returning RECORD has been
simplified to a RECORD constant or an inlined ROW() expression,
ExecInitFunctionScan failed to cross-check the function's result
rowtype against the coldeflist provided by the calling query.
That happened because get_expr_result_type is able to extract a
tupdesc from such expressions, which led ExecInitFunctionScan to
ignore the coldeflist.  (Instead, it used the extracted tupdesc
to check the function's output, which of course always succeeds.)

I have not been able to demonstrate any really serious consequences
from this, because if some column of the result is of the wrong
type and is directly referenced by a Var of the calling query,
CheckVarSlotCompatibility will catch it.  However, we definitely do
fail to report the case where the function returns more columns than
the coldeflist expects, and in the converse case where it returns
fewer columns, we get an assert failure (but, seemingly, no worse
results in non-assert builds).

To fix, always build the expected tupdesc from the coldeflist if there
is one, and consult get_expr_result_type only when there isn't one.

Also remove the failing Assert, even though it is no longer reached
after this fix.  It doesn't seem to be adding anything useful, since
later checking will deal with cases with the wrong number of columns.

The only other place I could find that is doing something similar
is inline_set_returning_function.  There's no live bug there because
we cannot be looking at a Const or RowExpr, but for consistency
change that code to agree with ExecInitFunctionScan.

Per report from PetSerAl.  After some debate I've concluded that
this should be back-patched.  There is a small risk that somebody
has been relying on such a case not throwing an error, but I judge
this outweighed by the risk that I've missed some way in which the
failure to cross-check has worse consequences than sketched above.

Discussion: https://postgr.es/m/CAKygsHSerA1eXsJHR9wft3Gn3wfHQ5RfP8XHBzF70_qcrrRvEg@mail.gmail.com

diff --git a/src/backend/executor/nodeFunctionscan.c b/src/backend/executor/nodeFunctionscan.c
index 0370f2e2b70ecfdef5b0c603863ad3130a15cb4e..6d3bec507c1952dbd382adbae3763dc5e5ea8db6 100644 (file)
--- a/src/backend/executor/nodeFunctionscan.c
+++ b/src/backend/executor/nodeFunctionscan.c
@@ -344,8 +344,6 @@ ExecInitFunctionScan(FunctionScan *node, EState *estate, int eflags)
                Node       *funcexpr = rtfunc->funcexpr;
                int                     colcount = rtfunc->funccolcount;
                FunctionScanPerFuncState *fs = &scanstate->funcstates[i];
-               TypeFuncClass functypclass;
-               Oid                     funcrettype;
                TupleDesc       tupdesc;
 
                fs->setexpr =
@@ -362,39 +360,18 @@ ExecInitFunctionScan(FunctionScan *node, EState *estate, int eflags)
                fs->rowcount = -1;
 
                /*
-                * Now determine if the function returns a simple or composite type,
-                * and build an appropriate tupdesc.  Note that in the composite case,
-                * the function may now return more columns than it did when the plan
-                * was made; we have to ignore any columns beyond "colcount".
+                * Now build a tupdesc showing the result type we expect from the
+                * function.  If we have a coldeflist then that takes priority (note
+                * the parser enforces that there is one if the function's nominal
+                * output type is RECORD).  Otherwise use get_expr_result_type.
+                *
+                * Note that if the function returns a named composite type, that may
+                * now contain more or different columns than it did when the plan was
+                * made.  For both that and the RECORD case, we need to check tuple
+                * compatibility.  ExecMakeTableFunctionResult handles some of this,
+                * and CheckVarSlotCompatibility provides a backstop.
                 */
-               functypclass = get_expr_result_type(funcexpr,
-                                                                                       &funcrettype,
-                                                                                       &tupdesc);
-
-               if (functypclass == TYPEFUNC_COMPOSITE ||
-                       functypclass == TYPEFUNC_COMPOSITE_DOMAIN)
-               {
-                       /* Composite data type, e.g. a table's row type */
-                       Assert(tupdesc);
-                       Assert(tupdesc->natts >= colcount);
-                       /* Must copy it out of typcache for safety */
-                       tupdesc = CreateTupleDescCopy(tupdesc);
-               }
-               else if (functypclass == TYPEFUNC_SCALAR)
-               {
-                       /* Base data type, i.e. scalar */
-                       tupdesc = CreateTemplateTupleDesc(1);
-                       TupleDescInitEntry(tupdesc,
-                                                          (AttrNumber) 1,
-                                                          NULL,        /* don't care about the name here */
-                                                          funcrettype,
-                                                          -1,
-                                                          0);
-                       TupleDescInitEntryCollation(tupdesc,
-                                                                               (AttrNumber) 1,
-                                                                               exprCollation(funcexpr));
-               }
-               else if (functypclass == TYPEFUNC_RECORD)
+               if (rtfunc->funccolnames != NIL)
                {
                        tupdesc = BuildDescFromLists(rtfunc->funccolnames,
                                                                                 rtfunc->funccoltypes,
@@ -410,8 +387,40 @@ ExecInitFunctionScan(FunctionScan *node, EState *estate, int eflags)
                }
                else
                {
-                       /* crummy error message, but parser should have caught this */
-                       elog(ERROR, "function in FROM has unsupported return type");
+                       TypeFuncClass functypclass;
+                       Oid                     funcrettype;
+
+                       functypclass = get_expr_result_type(funcexpr,
+                                                                                               &funcrettype,
+                                                                                               &tupdesc);
+
+                       if (functypclass == TYPEFUNC_COMPOSITE ||
+                               functypclass == TYPEFUNC_COMPOSITE_DOMAIN)
+                       {
+                               /* Composite data type, e.g. a table's row type */
+                               Assert(tupdesc);
+                               /* Must copy it out of typcache for safety */
+                               tupdesc = CreateTupleDescCopy(tupdesc);
+                       }
+                       else if (functypclass == TYPEFUNC_SCALAR)
+                       {
+                               /* Base data type, i.e. scalar */
+                               tupdesc = CreateTemplateTupleDesc(1);
+                               TupleDescInitEntry(tupdesc,
+                                                                  (AttrNumber) 1,
+                                                                  NULL,        /* don't care about the name here */
+                                                                  funcrettype,
+                                                                  -1,
+                                                                  0);
+                               TupleDescInitEntryCollation(tupdesc,
+                                                                                       (AttrNumber) 1,
+                                                                                       exprCollation(funcexpr));
+                       }
+                       else
+                       {
+                               /* crummy error message, but parser should have caught this */
+                               elog(ERROR, "function in FROM has unsupported return type");
+                       }
                }
 
                fs->tupdesc = tupdesc;

diff --git a/src/test/regress/expected/rangefuncs.out b/src/test/regress/expected/rangefuncs.out
index 36a5929113928a7a613b8572bebdb998f180ed2d..e7b569ed314d408524bbbfff0cb1580f42268ecd 100644 (file)
--- a/src/test/regress/expected/rangefuncs.out
+++ b/src/test/regress/expected/rangefuncs.out
@@ -2098,3 +2098,16 @@ select *, row_to_json(u) from unnest(array[]::rngfunc2[]) u;
 (0 rows)
 
 drop type rngfunc2;
+-- check detection of mismatching record types with a const-folded expression
+with a(b) as (values (row(1,2,3)))
+select * from a, coalesce(b) as c(d int, e int);  -- fail
+ERROR:  function return row and query-specified return row do not match
+DETAIL:  Returned row contains 3 attributes, but query expects 2.
+with a(b) as (values (row(1,2,3)))
+select * from a, coalesce(b) as c(d int, e int, f int, g int);  -- fail
+ERROR:  function return row and query-specified return row do not match
+DETAIL:  Returned row contains 3 attributes, but query expects 4.
+with a(b) as (values (row(1,2,3)))
+select * from a, coalesce(b) as c(d int, e int, f float);  -- fail
+ERROR:  function return row and query-specified return row do not match
+DETAIL:  Returned type integer at ordinal position 3, but query expects double precision.

diff --git a/src/test/regress/sql/rangefuncs.sql b/src/test/regress/sql/rangefuncs.sql
index 5d29d2e40124c0a87913fa31413373e4bfa931f5..6a56aedac167394834e4b85d1b486fbdea439863 100644 (file)
--- a/src/test/regress/sql/rangefuncs.sql
+++ b/src/test/regress/sql/rangefuncs.sql
@@ -656,3 +656,12 @@ select *, row_to_json(u) from unnest(array[null::rngfunc2, (1,'foo')::rngfunc2,
 select *, row_to_json(u) from unnest(array[]::rngfunc2[]) u;
 
 drop type rngfunc2;
+
+-- check detection of mismatching record types with a const-folded expression
+
+with a(b) as (values (row(1,2,3)))
+select * from a, coalesce(b) as c(d int, e int);  -- fail
+with a(b) as (values (row(1,2,3)))
+select * from a, coalesce(b) as c(d int, e int, f int, g int);  -- fail
+with a(b) as (values (row(1,2,3)))
+select * from a, coalesce(b) as c(d int, e int, f float);  -- fail