# Issue #61602: planner: wrong Join estimation depending on uninitialized or missing stats ## Metadata - Issue: https://github.com/pingcap/tidb/issues/61602 - Status: closed - Type: type/bug - Created At: 2025-06-09T11:14:05Z - Closed At: 2025-06-11T11:46:21Z - Labels: affects-6.5, affects-7.1, affects-7.5, affects-8.1, affects-8.5, epic/cardinality-estimation, report/customer, severity/major, sig/planner, type/bug ## Customer-Facing Phenomenon - Root Cause: 1. In join estimation, we use . 2. When deriving NDV from index-stats, we didn't check whether it was loaded or missing. After adding a new index without analyzing, the index-stats might be missing, 3. If it's missing, we'll use the wrong to calculate join estimation, and finally get a high error result. ## Linked PRs - Fix PR #61604: planner: fix the wrong join estimation depending on missing or uninitialized stats URL: https://github.com/pingcap/tidb/pull/61604 State: closed Merged At: 2025-06-11T11:46:19Z Changed Files Count: 5 Main Modules: tests/integrationtest, pkg/planner/core Sample Changed Files: - pkg/planner/core/stats.go - tests/integrationtest/r/executor/index_lookup_merge_join.result - tests/integrationtest/r/explain_complex.result - tests/integrationtest/r/planner/core/casetest/physicalplantest/physical_plan.result - tests/integrationtest/r/planner/core/indexjoin.result PR Summary: What problem does this PR solve? Problem Summary: planner: fix the wrong join estimation depending on missing or uninitialized stats What changed and how does it work? planner: fix the wrong join estimation depending on missing or uninitialized stats It's hard to construct test cases for this issue since it depends on stats cache's status. So I tested it locally, and this PR can work for this scenario: - Fix PR #61673: planner: fix the wrong join estimation depending on missing or uninitialized stats (#61604) URL: https://github.com/pingcap/tidb/pull/61673 State: open Merged At: not merged Changed Files Count: 5 Main Modules: tests/integrationtest, pkg/planner/core Sample Changed Files: - pkg/planner/core/stats.go - tests/integrationtest/r/executor/index_lookup_merge_join.result - tests/integrationtest/r/explain_complex.result - tests/integrationtest/r/planner/core/casetest/physicalplantest/physical_plan.result - tests/integrationtest/r/planner/core/indexjoin.result PR Summary: This is an automated cherry-pick of #61604 What problem does this PR solve? Problem Summary: planner: fix the wrong join estimation depending on missing or uninitialized stats What changed and how does it work? planner: fix the wrong join estimation depending on missing or uninitialized stats - Fix PR #61674: planner: fix the wrong join estimation depending on missing or uninitialized stats (#61604) URL: https://github.com/pingcap/tidb/pull/61674 State: closed Merged At: not merged Changed Files Count: 5 Main Modules: tests/integrationtest, cmd/explaintest, pkg/planner/core Sample Changed Files: - cmd/explaintest/r/explain_complex.result - pkg/planner/core/stats.go - tests/integrationtest/r/executor/index_lookup_merge_join.result - tests/integrationtest/r/planner/core/casetest/physicalplantest/physical_plan.result - tests/integrationtest/r/planner/core/indexjoin.result PR Summary: This is an automated cherry-pick of #61604 What problem does this PR solve? Problem Summary: planner: fix the wrong join estimation depending on missing or uninitialized stats What changed and how does it work? planner: fix the wrong join estimation depending on missing or uninitialized stats - Fix PR #61675: planner: fix the wrong join estimation depending on missing or uninitialized stats (#61604) URL: https://github.com/pingcap/tidb/pull/61675 State: open Merged At: not merged Changed Files Count: 5 Main Modules: tests/integrationtest, cmd/explaintest, pkg/planner/core Sample Changed Files: - cmd/explaintest/r/explain_complex.result - pkg/planner/core/stats.go - tests/integrationtest/r/executor/index_lookup_merge_join.result - tests/integrationtest/r/planner/core/casetest/physicalplantest/physical_plan.result - tests/integrationtest/r/planner/core/indexjoin.result PR Summary: This is an automated cherry-pick of #61604 What problem does this PR solve? Problem Summary: planner: fix the wrong join estimation depending on missing or uninitialized stats What changed and how does it work? planner: fix the wrong join estimation depending on missing or uninitialized stats - Fix PR #61676: planner: fix the wrong join estimation depending on missing or uninitialized stats (#61604) URL: https://github.com/pingcap/tidb/pull/61676 State: closed Merged At: 2025-07-22T02:43:20Z Changed Files Count: 3 Main Modules: pkg/planner/core, tests/integrationtest Sample Changed Files: - pkg/planner/core/casetest/physicalplantest/testdata/plan_suite_out.json - pkg/planner/core/stats.go - tests/integrationtest/r/explain_complex.result PR Summary: This is an automated cherry-pick of #61604 What problem does this PR solve? Problem Summary: planner: fix the wrong join estimation depending on missing or uninitialized stats What changed and how does it work? planner: fix the wrong join estimation depending on missing or uninitialized stats - Fix PR #61857: planner: fix the wrong join estimation depending on missing or uninitialized stats (#61604) URL: https://github.com/pingcap/tidb/pull/61857 State: closed Merged At: 2025-07-09T09:18:42Z Changed Files Count: 5 Main Modules: tests/integrationtest, pkg/planner/core Sample Changed Files: - pkg/planner/core/stats.go - tests/integrationtest/r/executor/index_lookup_merge_join.result - tests/integrationtest/r/explain_complex.result - tests/integrationtest/r/planner/core/casetest/physicalplantest/physical_plan.result - tests/integrationtest/r/planner/core/indexjoin.result PR Summary: This is an automated cherry-pick of #61604 What problem does this PR solve? Problem Summary: planner: fix the wrong join estimation depending on missing or uninitialized stats What changed and how does it work? planner: fix the wrong join estimation depending on missing or uninitialized stats ## Notes - At least one merged PR was found. The merge timestamp above can be used as the fix landing time in the main branch.