planner: not allow the optimizer to use json_contains(j, '[]') as a…

…ccess conditions on MVIndex (pingcap#41013)

ref pingcap#40191

planner/core/indexmerge_path.go

@@ -668,7 +668,7 @@ func (ds *DataSource) buildPartialPaths4MVIndex(accessFilters []expression.Expre
  case ast.JSONContains: // (json_contains(a->'$.zip', '[1, 2, 3]')
  isIntersection = true
  virColVals, ok = jsonArrayExpr2Exprs(ds.ctx, sf.GetArgs()[1], jsonType)
- if !ok {
+ if !ok || len(virColVals) == 0 { // json_contains(JSON, '[]') is TRUE
  return nil, false, false, nil
  }
  case ast.JSONOverlaps: // (json_overlaps(a->'$.zip', '[1, 2, 3]')
@@ -682,7 +682,7 @@ func (ds *DataSource) buildPartialPaths4MVIndex(accessFilters []expression.Expre
  }
  var ok bool
  virColVals, ok = jsonArrayExpr2Exprs(ds.ctx, sf.GetArgs()[1-jsonPathIdx], jsonType)
- if !ok {
+ if !ok || len(virColVals) == 0 { // forbid empty array for safety
  return nil, false, false, nil
  }
  default:

planner/core/indexmerge_path_test.go

@@ -302,6 +302,31 @@ func TestMVIndexFullScan(t *testing.T) {
  tk.MustGetErrMsg(`select /*+ use_index(t, kj) */ count(*) from t`, "[planner:1815]Internal : Can't find a proper physical plan for this query")
 }
 
+func TestMVIndexEmptyArray(t *testing.T) {
+ store := testkit.CreateMockStore(t)
+ tk := testkit.NewTestKit(t, store)
+ tk.MustExec("use test")
+ tk.MustExec(`create table t(j json, index kj((cast(j as signed array))))`)
+ tk.MustExec(`insert into t values ('[1]')`)
+ tk.MustExec(`insert into t values ('[1, 2]')`)
+ tk.MustExec(`insert into t values ('[]')`)
+ tk.MustExec(`insert into t values (NULL)`)
+
+ for _, cond := range []string{
+ "json_contains(j, '[]')",
+ "json_contains(j, '[1]')",
+ "json_contains(j, '[1, 2]')",
+ "json_contains(j, '[1, 10]')",
+ "json_overlaps(j, '[]')",
+ "json_overlaps(j, '[1]')",
+ "json_overlaps(j, '[1, 2]')",
+ "json_overlaps(j, '[1, 10]')",
+ } {
+ tk.MustQuery(fmt.Sprintf("select /*+ use_index_merge(t) */ * from t where %v", cond)).Sort().Check(
+ tk.MustQuery(fmt.Sprintf("select /*+ ignore_index(t, kj) */ * from t where %v", cond)).Sort().Rows())
+ }
+}
+
 func TestMVIndexRandom(t *testing.T) {
  store := testkit.CreateMockStore(t)
  tk := testkit.NewTestKit(t, store)
@@ -364,14 +389,23 @@ func randMVIndexCond(condType int, valOpts randMVIndexValOpts) string {
  case 0: // member_of
  return fmt.Sprintf(`(%v member of (j))`, randMVIndexValue(valOpts))
  case 1: // json_contains
- return fmt.Sprintf(`json_contains(j, '[%v, %v]')`, randMVIndexValue(valOpts), randMVIndexValue(valOpts))
+ return fmt.Sprintf(`json_contains(j, '%v')`, randArray(valOpts))
  case 2: // json_overlaps
- return fmt.Sprintf(`json_overlaps(j, '[%v, %v]')`, randMVIndexValue(valOpts), randMVIndexValue(valOpts))
+ return fmt.Sprintf(`json_overlaps(j, '%v')`, randArray(valOpts))
  default: // others
  return fmt.Sprintf(`a < %v`, rand.Intn(valOpts.distinct))
  }
 }
 
+func randArray(opts randMVIndexValOpts) string {
+ n := rand.Intn(5) // n can be 0
+ var vals []string
+ for i := 0; i < n; i++ {
+ vals = append(vals, randMVIndexValue(opts))
+ }
+ return "[" + strings.Join(vals, ", ") + "]"
+}
+
 type randMVIndexValOpts struct {
  valType string // INT, UNSIGNED, STR, DATE
  maxStrLen int