MAXALIGN the target address where we store flattened value.

Amit Kapila · Amit Kapila · commit dca44d07c585 · 2018-10-03T09:54:01.000+05:30
The API (EOH_flatten_into) that flattens the expanded value representation expects the target address to be maxaligned. All it's usage adhere to that principle except when serializing datums for parallel query. Fix that usage. Diagnosed-by: Tom Lane Author: Tom Lane and Amit Kapila Backpatch-through: 9.6 Discussion: https://postgr.es/m/11629.1536550032@sss.pgh.pa.us
diff --git a/src/backend/utils/adt/datum.c b/src/backend/utils/adt/datum.c
@@ -334,8 +334,19 @@ datumSerialize(Datum value, bool isnull, bool typByVal, int typLen,
 		}
 		else if (eoh)
 		{
-			EOH_flatten_into(eoh, (void *) *start_address, header);
+			char	   *tmp;
+
+			/*
+			 * EOH_flatten_into expects the target address to be maxaligned,
+			 * so we can't store directly to *start_address.
+			 */
+			tmp = (char *) palloc(header);
+			EOH_flatten_into(eoh, (void *) tmp, header);
+			memcpy(*start_address, tmp, header);
 			*start_address += header;
+
+			/* be tidy. */
+			pfree(tmp);
 		}
 		else
 		{
diff --git a/src/test/regress/expected/select_parallel.out b/src/test/regress/expected/select_parallel.out
@@ -235,6 +235,33 @@ explain (costs off)
          Index Cond: (unique1 = 1)
 (5 rows)
 
+-- test passing expanded-value representations to workers
+CREATE FUNCTION make_some_array(int,int) returns int[] as
+$$declare x int[];
+  begin
+    x[1] := $1;
+    x[2] := $2;
+    return x;
+  end$$ language plpgsql parallel safe;
+CREATE TABLE fooarr(f1 text, f2 int[], f3 text);
+INSERT INTO fooarr VALUES('1', ARRAY[1,2], 'one');
+PREPARE pstmt(text, int[]) AS SELECT * FROM fooarr WHERE f1 = $1 AND f2 = $2;
+EXPLAIN (COSTS OFF) EXECUTE pstmt('1', make_some_array(1,2));
+                            QUERY PLAN                            
+------------------------------------------------------------------
+ Gather
+   Workers Planned: 3
+   ->  Parallel Seq Scan on fooarr
+         Filter: ((f1 = '1'::text) AND (f2 = '{1,2}'::integer[]))
+(4 rows)
+
+EXECUTE pstmt('1', make_some_array(1,2));
+ f1 |  f2   | f3  
+----+-------+-----
+ 1  | {1,2} | one
+(1 row)
+
+DEALLOCATE pstmt;
 do $$begin
   -- Provoke error, possibly in worker.  If this error happens to occur in
   -- the worker, there will be a CONTEXT line which must be hidden.
diff --git a/src/test/regress/sql/select_parallel.sql b/src/test/regress/sql/select_parallel.sql
@@ -96,6 +96,22 @@ explain (costs off)
 explain (costs off)
   select stringu1::int2 from tenk1 where unique1 = 1;
 
+-- test passing expanded-value representations to workers
+CREATE FUNCTION make_some_array(int,int) returns int[] as
+$$declare x int[];
+  begin
+    x[1] := $1;
+    x[2] := $2;
+    return x;
+  end$$ language plpgsql parallel safe;
+CREATE TABLE fooarr(f1 text, f2 int[], f3 text);
+INSERT INTO fooarr VALUES('1', ARRAY[1,2], 'one');
+
+PREPARE pstmt(text, int[]) AS SELECT * FROM fooarr WHERE f1 = $1 AND f2 = $2;
+EXPLAIN (COSTS OFF) EXECUTE pstmt('1', make_some_array(1,2));
+EXECUTE pstmt('1', make_some_array(1,2));
+DEALLOCATE pstmt;
+
 do $$begin
   -- Provoke error, possibly in worker.  If this error happens to occur in
   -- the worker, there will be a CONTEXT line which must be hidden.

Original file line number	Diff line number	Diff line change
`@@ -334,8 +334,19 @@ datumSerialize(Datum value, bool isnull, bool typByVal, int typLen,`
`334`	`334`	`}`
`335`	`335`	`else if (eoh)`
`336`	`336`	`{`
`337`		`- EOH_flatten_into(eoh, (void ) start_address, header);`
	`337`	`+ char *tmp;`
	`338`	`+`
	`339`	`+ /*`
	`340`	`+ * EOH_flatten_into expects the target address to be maxaligned,`
	`341`	`+ * so we can't store directly to *start_address.`
	`342`	`+ */`
	`343`	`+ tmp = (char *) palloc(header);`
	`344`	`+ EOH_flatten_into(eoh, (void *) tmp, header);`
	`345`	`+ memcpy(*start_address, tmp, header);`
`338`	`346`	`*start_address += header;`
	`347`	`+`
	`348`	`+ /* be tidy. */`
	`349`	`+ pfree(tmp);`
`339`	`350`	`}`
`340`	`351`	`else`
`341`	`352`	`{`