Groupby recursion cleanup - [MOD-7245] (#4598)

* cleanup recursion

* added a test

* remove unreachable code

src/aggregate/group_by.c

@@ -162,14 +162,11 @@ static void invokeReducers(Grouper *g, Group *gr, RLookupRow *srcrow) {
  *  the `GROUPER_NSRCKEYS(g)` macro
  * @param xpos the current position in xarr
  * @param xlen cached value of GROUPER_NSRCKEYS
- * @param ypos if xarr[xpos] is an array, this is the current position within
- *  the array
  * @param hval current X-wise hash value. Note that members of the same Y array
  *  are not hashed together.
  * @param res the row is passed to each reducer
  */
-static void extractGroups(Grouper *g, const RSValue **xarr, size_t xpos, size_t xlen, size_t arridx,
-                          uint64_t hval, RLookupRow *res) {
+static void extractGroups(Grouper *g, const RSValue **xarr, size_t xpos, size_t xlen, uint64_t hval, RLookupRow *res) {
   // end of the line - create/add to group
   if (xpos == xlen) {
     Group *group = NULL;
@@ -193,31 +190,26 @@ static void extractGroups(Grouper *g, const RSValue **xarr, size_t xpos, size_t
   // regular value - just move one step -- increment XPOS
   if (v->t != RSValue_Array) {
     hval = RSValue_Hash(v, hval);
-    extractGroups(g, xarr, xpos + 1, xlen, 0, hval, res);
+    extractGroups(g, xarr, xpos + 1, xlen, hval, res);
+  } else if (RSValue_ArrayLen(v) == 0) {
+    // Empty array - hash as null
+    hval = RSValue_Hash(RS_NullVal(), hval);
+    const RSValue *array = xarr[xpos];
+    xarr[xpos] = RS_NullVal();
+    extractGroups(g, xarr, xpos + 1, xlen, hval, res);
+    xarr[xpos] = array;
   } else {
-    // Array value. Replace current XPOS with child temporarily
+    // Array value. Replace current XPOS with child temporarily.
+    // Each value in the array will be a separate group
     const RSValue *array = xarr[xpos];
-    const RSValue *elem;
-
-    if (arridx >= RSValue_ArrayLen(v)) {
-      elem = NULL;
-    } else {
-      elem = RSValue_ArrayItem(v, arridx);
+    for (size_t i = 0; i < RSValue_ArrayLen(v); i++) {
+      const RSValue *elem = RSValue_ArrayItem(v, i);
+      // hash the element, even if it's an array
+      uint64_t hh = RSValue_Hash(elem, hval);
+      xarr[xpos] = elem;
+      extractGroups(g, xarr, xpos + 1, xlen, hh, res);
     }
-
-    if (elem == NULL) {
-      elem = RS_NullVal();
-    }
-    uint64_t hh = RSValue_Hash(elem, hval);
-
-    xarr[xpos] = elem;
-    extractGroups(g, xarr, xpos, xlen, arridx, hh, res);
     xarr[xpos] = array;
-
-    // Replace the value back, and proceed to the next value of the array
-    if (++arridx < RSValue_ArrayLen(v)) {
-      extractGroups(g, xarr, xpos, xlen, arridx, hval, res);
-    }
   }
 }
 
@@ -234,7 +226,7 @@ static void invokeGroupReducers(Grouper *g, RLookupRow *srcrow) {
     }
     groupvals[ii] = v;
   }
-  extractGroups(g, groupvals, 0, nkeys, 0, 0, srcrow);
+  extractGroups(g, groupvals, 0, nkeys, 0, srcrow);
 }
 
 static int Grouper_rpAccum(ResultProcessor *base, SearchResult *res) {

tests/pytests/test_aggregate.py

@@ -706,6 +706,26 @@ def testAggregateGroupByOnEmptyField(env):
     for var in expected:
         env.assertContains(var, res)
 
+def test_groupby_array(env: Env):
+  env.expect('FT.CREATE', 'idx', 'SCHEMA', 't1', 'TEXT', 'SORTABLE', 't2', 'TEXT', 'SORTABLE').ok()
+  with env.getClusterConnectionIfNeeded() as con:
+    con.execute_command('HSET', 'doc1', 't1', 'foo,bar', 't2', 'baz,qux')
+
+  res = env.cmd('FT.AGGREGATE', 'idx', '*',
+                'APPLY', 'split(@t1, ",")', 'AS', 't1',
+                'APPLY', 'split(@t2, ",")', 'AS', 't2',
+                'GROUPBY', '2', '@t1', '@t2')
+
+  exp = [4, ['t1', 'foo', 't2', 'baz'],
+            ['t1', 'foo', 't2', 'qux'],
+            ['t1', 'bar', 't2', 'baz'],
+            ['t1', 'bar', 't2', 'qux']]
+
+  # Check that the result is as expected (res elements contained in exp, and same size)
+  for row in res:
+    env.assertContains(row, exp)
+  env.assertEqual(len(res), len(exp), message=f'{res} != {exp}')
+
 def testMultiSortBy(env):
     conn = getConnectionByEnv(env)
     env.cmd('FT.CREATE', 'sb_idx', 'SCHEMA', 't1', 'TEXT', 't2', 'TEXT')