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

tglsfdc · tglsfdc · commit 2ed8f9a01e74 · 2024-03-06T14:41:13.000-05:00
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
@@ -343,8 +343,6 @@ 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 =
@@ -361,39 +359,18 @@ 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,
@@ -409,8 +386,40 @@ 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/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
@@ -5216,16 +5216,20 @@ inline_set_returning_function(PlannerInfo *root, RangeTblEntry *rte)
 	}
 
 	/*
-	 * Also resolve the actual function result tupdesc, if composite.  If the
-	 * function is just declared to return RECORD, dig the info out of the AS
-	 * clause.
+	 * Also resolve the actual function result tupdesc, if composite.  If we
+	 * have a coldeflist, believe that; otherwise use get_expr_result_type.
+	 * (This logic should match ExecInitFunctionScan.)
 	 */
-	functypclass = get_expr_result_type((Node *) fexpr, NULL, &rettupdesc);
-	if (functypclass == TYPEFUNC_RECORD)
+	if (rtfunc->funccolnames != NIL)
+	{
+		functypclass = TYPEFUNC_RECORD;
 		rettupdesc = BuildDescFromLists(rtfunc->funccolnames,
 										rtfunc->funccoltypes,
 										rtfunc->funccoltypmods,
 										rtfunc->funccolcollations);
+	}
+	else
+		functypclass = get_expr_result_type((Node *) fexpr, NULL, &rettupdesc);
 
 	/*
 	 * The single command must be a plain SELECT.
diff --git a/src/test/regress/expected/rangefuncs.out b/src/test/regress/expected/rangefuncs.out
@@ -2485,3 +2485,16 @@ select * from
  [{"id": "1"}] | 1
 (1 row)
 
+-- 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
@@ -815,3 +815,12 @@ select * from
    from unnest(array['{"lectures": [{"id": "1"}]}'::jsonb])
         as unnested_modules(module)) as ss,
   jsonb_to_recordset(ss.lecture) as j (id text);
+
+-- 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
