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planner/core: raise warning for unmatched join hint #9914

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merged 5 commits into from
Apr 1, 2019
Merged

planner/core: raise warning for unmatched join hint #9914

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2abcda0
planner/core: raise warning for unmatched join hint
alivxxx Mar 27, 2019
9b8c4d9
address comments
alivxxx Mar 28, 2019
35c72a9
address comments
alivxxx Mar 29, 2019
53165aa
Merge branch 'master' into join-hint
eurekaka Apr 1, 2019
90a2b09
Merge branch 'master' into join-hint
XuHuaiyu Apr 1, 2019
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2 changes: 1 addition & 1 deletion planner/core/exhaust_physical_plans.go
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Original file line number Diff line number Diff line change
Expand Up @@ -637,7 +637,7 @@ func (p *LogicalJoin) tryToGetIndexJoin(prop *property.PhysicalProperty) (indexJ
// Construct warning message prefix.
errMsg := "Optimizer Hint TIDB_INLJ is inapplicable"
if p.hintInfo != nil {
errMsg = fmt.Sprintf("Optimizer Hint %s is inapplicable", p.hintInfo.restore2IndexJoinHint())
errMsg = fmt.Sprintf("Optimizer Hint %s is inapplicable", restore2JoinHint(TiDBIndexNestedLoopJoin, p.hintInfo.indexNestedLoopJoinHint))
}

// Append inapplicable reason.
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18 changes: 15 additions & 3 deletions planner/core/logical_plan_builder.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1853,19 +1853,31 @@ func (b *PlanBuilder) pushTableHints(hints []*ast.TableOptimizerHint) bool {
}
if len(sortMergeTables)+len(INLJTables)+len(hashJoinTables) > 0 {
b.tableHintInfo = append(b.tableHintInfo, tableHintInfo{
sortMergeJoinTables: sortMergeTables,
indexNestedLoopJoinTables: INLJTables,
hashJoinTables: hashJoinTables,
sortMergeJoinHint: joinHintInfo{tables: sortMergeTables},
indexNestedLoopJoinHint: joinHintInfo{tables: INLJTables},
hashJoinHint: joinHintInfo{tables: hashJoinTables},
})
return true
}
return false
}

func (b *PlanBuilder) popTableHints() {
hintInfo := b.tableHintInfo[len(b.tableHintInfo)-1]
b.appendUnmatchedJoinHintWarning(TiDBIndexNestedLoopJoin, hintInfo.indexNestedLoopJoinHint)
b.appendUnmatchedJoinHintWarning(TiDBMergeJoin, hintInfo.sortMergeJoinHint)
b.appendUnmatchedJoinHintWarning(TiDBHashJoin, hintInfo.hashJoinHint)
b.tableHintInfo = b.tableHintInfo[:len(b.tableHintInfo)-1]
}

func (b *PlanBuilder) appendUnmatchedJoinHintWarning(joinType string, hintInfo joinHintInfo) {
if len(hintInfo.tables) == 0 || hintInfo.matched {
return
}
errMsg := fmt.Sprintf("Optimizer Hint %s is inapplicable because there are no matching table names. Maybe you can use the table alias name", restore2JoinHint(joinType, hintInfo))
b.ctx.GetSessionVars().StmtCtx.AppendWarning(ErrInternal.GenWithStack(errMsg))
}

// TableHints returns the *tableHintInfo of PlanBuilder.
func (b *PlanBuilder) TableHints() *tableHintInfo {
if len(b.tableHintInfo) == 0 {
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55 changes: 55 additions & 0 deletions planner/core/physical_plan_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,7 @@ import (
"github.com/pingcap/tidb/planner/core"
"github.com/pingcap/tidb/session"
"github.com/pingcap/tidb/sessionctx"
"github.com/pingcap/tidb/sessionctx/stmtctx"
"github.com/pingcap/tidb/util/testleak"
)

Expand Down Expand Up @@ -1434,3 +1435,57 @@ func (s *testPlanSuite) TestSemiJoinToInner(c *C) {
c.Assert(err, IsNil)
c.Assert(core.ToString(p), Equals, "Apply{TableReader(Table(t))->IndexJoin{IndexReader(Index(t.c_d_e)[[NULL,+inf]]->HashAgg)->HashAgg->IndexReader(Index(t.g)[[NULL,+inf]])}(t3.d,t2.g)}->StreamAgg")
}

func (s *testPlanSuite) TestUnmatchedJoinHint(c *C) {
defer testleak.AfterTest(c)()
store, dom, err := newStoreWithBootstrap()
c.Assert(err, IsNil)
defer func() {
dom.Close()
store.Close()
}()
se, err := session.CreateSession4Test(store)
c.Assert(err, IsNil)
_, err = se.Execute(context.Background(), "use test")
c.Assert(err, IsNil)
tests := []struct {
sql string
warning string
}{
{
sql: "SELECT /*+ TIDB_SMJ(t3, t4) */ * from t t1, t t2 where t1.a = t2.a",
warning: "[planner:1815]Optimizer Hint /*+ TIDB_SMJ(t3, t4) */ is inapplicable because there are no matching table names. Maybe you can use the table alias name",
},
{
sql: "SELECT /*+ TIDB_HJ(t3, t4) */ * from t t1, t t2 where t1.a = t2.a",
warning: "[planner:1815]Optimizer Hint /*+ TIDB_HJ(t3, t4) */ is inapplicable because there are no matching table names. Maybe you can use the table alias name",
},
{
sql: "SELECT /*+ TIDB_INLJ(t3, t4) */ * from t t1, t t2 where t1.a = t2.a",
warning: "[planner:1815]Optimizer Hint /*+ TIDB_INLJ(t3, t4) */ is inapplicable because there are no matching table names. Maybe you can use the table alias name",
},
{
sql: "SELECT /*+ TIDB_SMJ(t1, t2) */ * from t t1, t t2 where t1.a = t2.a",
warning: "",
},
{
sql: "SELECT /*+ TIDB_SMJ(t3, t4) */ * from t t1, t t2, t t3 where t1.a = t2.a and t2.a = t3.a",
warning: "",
},
}
for _, test := range tests {
se.GetSessionVars().StmtCtx.SetWarnings(nil)
stmt, err := s.ParseOneStmt(test.sql, "", "")
c.Assert(err, IsNil)
_, err = planner.Optimize(se, stmt, s.is)
c.Assert(err, IsNil)
warnings := se.GetSessionVars().StmtCtx.GetWarnings()
if test.warning == "" {
c.Assert(len(warnings), Equals, 0)
} else {
c.Assert(len(warnings), Equals, 1)
c.Assert(warnings[0].Level, Equals, stmtctx.WarnLevelWarning)
c.Assert(warnings[0].Err.Error(), Equals, test.warning)
}
}
}
33 changes: 21 additions & 12 deletions planner/core/planbuilder.go
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Original file line number Diff line number Diff line change
Expand Up @@ -47,21 +47,26 @@ type visitInfo struct {
}

type tableHintInfo struct {
indexNestedLoopJoinTables []model.CIStr
sortMergeJoinTables []model.CIStr
hashJoinTables []model.CIStr
indexNestedLoopJoinHint joinHintInfo
sortMergeJoinHint joinHintInfo
hashJoinHint joinHintInfo
}

type joinHintInfo struct {
tables []model.CIStr
matched bool
}

func (info *tableHintInfo) ifPreferMergeJoin(tableNames ...*model.CIStr) bool {
return info.matchTableName(tableNames, info.sortMergeJoinTables)
return info.matchTableName(tableNames, &info.sortMergeJoinHint)
}

func (info *tableHintInfo) ifPreferHashJoin(tableNames ...*model.CIStr) bool {
return info.matchTableName(tableNames, info.hashJoinTables)
return info.matchTableName(tableNames, &info.hashJoinHint)
}

func (info *tableHintInfo) ifPreferINLJ(tableNames ...*model.CIStr) bool {
return info.matchTableName(tableNames, info.indexNestedLoopJoinTables)
return info.matchTableName(tableNames, &info.indexNestedLoopJoinHint)
}

// matchTableName checks whether the hint hit the need.
Expand All @@ -72,25 +77,29 @@ func (info *tableHintInfo) ifPreferINLJ(tableNames ...*model.CIStr) bool {
// Which it joins on with depend on sequence of traverse
// and without reorder, user might adjust themselves.
// This is similar to MySQL hints.
func (info *tableHintInfo) matchTableName(tables []*model.CIStr, tablesInHints []model.CIStr) bool {
func (info *tableHintInfo) matchTableName(tables []*model.CIStr, joinHint *joinHintInfo) bool {
for _, tableName := range tables {
if tableName == nil {
continue
}
for _, curEntry := range tablesInHints {
for _, curEntry := range joinHint.tables {
if curEntry.L == tableName.L {
joinHint.matched = true
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Do we need to mark hint as unmatched if any specified hint table cannot find a match? /cc @morgo

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The default value is false, is unmatched?

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I mean if the hint contains t1 and t2, while the query only involves t2, should we raise warning?

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If so, maybe it's more reasonable to raise a warning.

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Can we define the matched as a string slice?
Thus we can print the accurate wrong table name in the warning message

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Warning sounds good to me. Note that in some cases, MySQL hints do not even raise warnings because they are considered hints (entirely optional to enforce vs. directives). I think we should just arrive at warnings and never errors.

return true
}
}
}
return false
}

func (info *tableHintInfo) restore2IndexJoinHint() string {
buffer := bytes.NewBufferString("/*+ TIDB_INLJ(")
for i, tableName := range info.indexNestedLoopJoinTables {
func restore2JoinHint(joinType string, joinHint joinHintInfo) string {
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buffer := bytes.NewBufferString("/*+ ")
buffer.WriteString(strings.ToUpper(joinType))
buffer.WriteString("(")
tables := joinHint.tables
for i, tableName := range tables {
buffer.WriteString(tableName.O)
if i < len(info.indexNestedLoopJoinTables)-1 {
if i < len(tables)-1 {
buffer.WriteString(", ")
}
}
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