Fix incorrect logic in plpgsql for cleanup after evaluation of non-simple

expressions.  We need to deal with this when handling subscripts in an array
assignment, and also when catching an exception.  In an Assert-enabled build
these omissions led to Assert failures, but I think in a normal build the
only consequence would be short-term memory leakage; which may explain why
this wasn't reported from the field long ago.

Back-patch to all supported versions.  7.4 doesn't have exceptions, but
otherwise these bugs go all the way back.

Heikki Linnakangas and Tom Lane

diff --git a/src/pl/plpgsql/src/pl_exec.c b/src/pl/plpgsql/src/pl_exec.c
index 04f3638510200903c89c8beb3cd3e16ee6e7ef02..d83756f7cf224300f2f8613138e18acb07f0c1ae 100644 (file)
--- a/src/pl/plpgsql/src/pl_exec.c
+++ b/src/pl/plpgsql/src/pl_exec.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *   $PostgreSQL: pgsql/src/pl/plpgsql/src/pl_exec.c,v 1.244.2.6 2010/07/05 09:27:24 heikki Exp $
+ *   $PostgreSQL: pgsql/src/pl/plpgsql/src/pl_exec.c,v 1.244.2.7 2010/08/09 18:50:29 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1076,6 +1076,9 @@ exec_stmt_block(PLpgSQL_execstate *estate, PLpgSQL_stmt_block *block)
             */
            SPI_restore_connection();
 
+           /* Must clean up the econtext too */
+           exec_eval_cleanup(estate);
+
            /* Look for a matching exception handler */
            foreach(e, block->exceptions->exc_list)
            {
@@ -2636,6 +2639,9 @@ plpgsql_estate_setup(PLpgSQL_execstate *estate,
  *
  * NB: the result of the evaluation is no longer valid after this is done,
  * unless it is a pass-by-value datatype.
+ *
+ * NB: if you change this code, see also the hacks in exec_assign_value's
+ * PLPGSQL_DTYPE_ARRAYELEM case.
  * ----------
  */
 static void
@@ -3443,6 +3449,10 @@ exec_assign_expr(PLpgSQL_execstate *estate, PLpgSQL_datum *target,
 
 /* ----------
  * exec_assign_value           Put a value into a target field
+ *
+ * Note: in some code paths, this may leak memory in the eval_econtext;
+ * we assume that will be cleaned up later by exec_eval_cleanup.  We cannot
+ * call exec_eval_cleanup here for fear of destroying the input Datum value.
  * ----------
  */
 static void
@@ -3693,6 +3703,9 @@ exec_assign_value(PLpgSQL_execstate *estate,
 
        case PLPGSQL_DTYPE_ARRAYELEM:
            {
+               /*
+                * Target is an element of an array
+                */
                int         nsubscripts;
                int         i;
                PLpgSQL_expr *subscripts[MAXDIM];
@@ -3708,10 +3721,19 @@ exec_assign_value(PLpgSQL_execstate *estate,
                            coerced_value;
                ArrayType  *oldarrayval;
                ArrayType  *newarrayval;
+               SPITupleTable *save_eval_tuptable;
+
+               /*
+                * We need to do subscript evaluation, which might require
+                * evaluating general expressions; and the caller might have
+                * done that too in order to prepare the input Datum.  We
+                * have to save and restore the caller's SPI_execute result,
+                * if any.
+                */
+               save_eval_tuptable = estate->eval_tuptable;
+               estate->eval_tuptable = NULL;
 
                /*
-                * Target is an element of an array
-                *
                 * To handle constructs like x[1][2] := something, we have to
                 * be prepared to deal with a chain of arrayelem datums. Chase
                 * back to find the base array datum, and save the subscript
@@ -3765,8 +3787,23 @@ exec_assign_value(PLpgSQL_execstate *estate,
                        ereport(ERROR,
                                (errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
                                 errmsg("array subscript in assignment must not be null")));
+
+                   /*
+                    * Clean up in case the subscript expression wasn't simple.
+                    * We can't do exec_eval_cleanup, but we can do this much
+                    * (which is safe because the integer subscript value is
+                    * surely pass-by-value), and we must do it in case the
+                    * next subscript expression isn't simple either.
+                    */
+                   if (estate->eval_tuptable != NULL)
+                       SPI_freetuptable(estate->eval_tuptable);
+                   estate->eval_tuptable = NULL;
                }
 
+               /* Now we can restore caller's SPI_execute result if any. */
+               Assert(estate->eval_tuptable == NULL);
+               estate->eval_tuptable = save_eval_tuptable;
+
                /* Coerce source value to match array element type. */
                coerced_value = exec_simple_cast_value(value,
                                                       valtype,

diff --git a/src/test/regress/expected/plpgsql.out b/src/test/regress/expected/plpgsql.out
index 0446f5193cde9e665bf7976f5a2bd7ed0e5dd822..9a9e4d35a62062839486e7f617755275d13c0fe8 100644 (file)
--- a/src/test/regress/expected/plpgsql.out
+++ b/src/test/regress/expected/plpgsql.out
@@ -3737,6 +3737,49 @@ SELECT * FROM leaker_1(true);
 
 DROP FUNCTION leaker_1(bool);
 DROP FUNCTION leaker_2(bool);
+-- Test for appropriate cleanup of non-simple expression evaluations
+-- (bug in all versions prior to August 2010)
+CREATE FUNCTION nonsimple_expr_test() RETURNS text[] AS $$
+DECLARE
+  arr text[];
+  lr text;
+  i integer;
+BEGIN
+  arr := array[array['foo','bar'], array['baz', 'quux']];
+  lr := 'fool';
+  i := 1;
+  -- use sub-SELECTs to make expressions non-simple
+  arr[(SELECT i)][(SELECT i+1)] := (SELECT lr);
+  RETURN arr;
+END;
+$$ LANGUAGE plpgsql;
+SELECT nonsimple_expr_test();
+   nonsimple_expr_test   
+-------------------------
+ {{foo,fool},{baz,quux}}
+(1 row)
+
+DROP FUNCTION nonsimple_expr_test();
+CREATE FUNCTION nonsimple_expr_test() RETURNS integer AS $$
+declare
+   i integer NOT NULL := 0;
+begin
+  begin
+    i := (SELECT NULL::integer);  -- should throw error
+  exception
+    WHEN OTHERS THEN
+      i := (SELECT 1::integer);
+  end;
+  return i;
+end;
+$$ LANGUAGE plpgsql;
+SELECT nonsimple_expr_test();
+ nonsimple_expr_test 
+---------------------
+                   1
+(1 row)
+
+DROP FUNCTION nonsimple_expr_test();
 -- Test handling of string literals.
 set standard_conforming_strings = off;
 create or replace function strtest() returns text as $$

diff --git a/src/test/regress/sql/plpgsql.sql b/src/test/regress/sql/plpgsql.sql
index 3dcfc9e7813e93bd4d02bf8960ed7f7736998375..afd9c528ca2b525c56f196c2da875a4aa813a926 100644 (file)
--- a/src/test/regress/sql/plpgsql.sql
+++ b/src/test/regress/sql/plpgsql.sql
@@ -3006,6 +3006,46 @@ SELECT * FROM leaker_1(true);
 DROP FUNCTION leaker_1(bool);
 DROP FUNCTION leaker_2(bool);
 
+-- Test for appropriate cleanup of non-simple expression evaluations
+-- (bug in all versions prior to August 2010)
+
+CREATE FUNCTION nonsimple_expr_test() RETURNS text[] AS $$
+DECLARE
+  arr text[];
+  lr text;
+  i integer;
+BEGIN
+  arr := array[array['foo','bar'], array['baz', 'quux']];
+  lr := 'fool';
+  i := 1;
+  -- use sub-SELECTs to make expressions non-simple
+  arr[(SELECT i)][(SELECT i+1)] := (SELECT lr);
+  RETURN arr;
+END;
+$$ LANGUAGE plpgsql;
+
+SELECT nonsimple_expr_test();
+
+DROP FUNCTION nonsimple_expr_test();
+
+CREATE FUNCTION nonsimple_expr_test() RETURNS integer AS $$
+declare
+   i integer NOT NULL := 0;
+begin
+  begin
+    i := (SELECT NULL::integer);  -- should throw error
+  exception
+    WHEN OTHERS THEN
+      i := (SELECT 1::integer);
+  end;
+  return i;
+end;
+$$ LANGUAGE plpgsql;
+
+SELECT nonsimple_expr_test();
+
+DROP FUNCTION nonsimple_expr_test();
+
 -- Test handling of string literals.
 
 set standard_conforming_strings = off;