planner: add more test cases for non-prep plan cache

planner/core/plan_cache.go

@@ -115,6 +115,10 @@ func planCachePreprocess(ctx context.Context, sctx sessionctx.Context, isNonPrep
 func GetPlanFromSessionPlanCache(ctx context.Context, sctx sessionctx.Context,
 	isNonPrepared bool, is infoschema.InfoSchema, stmt *PlanCacheStmt,
 	params []expression.Expression) (plan Plan, names []*types.FieldName, err error) {
+	if v := ctx.Value("____GetPlanFromSessionPlanCacheErr"); v != nil { // for testing
+		return nil, nil, errors.New("____GetPlanFromSessionPlanCacheErr")
+	}
+
 	if err := planCachePreprocess(ctx, sctx, isNonPrepared, is, stmt, params); err != nil {
 		return nil, nil, err
 	}

planner/core/plan_cache_param.go

@@ -15,6 +15,7 @@
 package core
 
 import (
+	"context"
 	"errors"
 	"strings"
 	"sync"
@@ -70,7 +71,7 @@ func (pr *paramReplacer) Reset() { pr.params = nil }
 // ParameterizeAST parameterizes this StmtNode.
 // e.g. `select * from t where a<10 and b<23` --> `select * from t where a<? and b<?`, [10, 23].
 // NOTICE: this function may modify the input stmt.
-func ParameterizeAST(sctx sessionctx.Context, stmt ast.StmtNode) (paramSQL string, params []*driver.ValueExpr, err error) {
+func ParameterizeAST(ctx context.Context, sctx sessionctx.Context, stmt ast.StmtNode) (paramSQL string, params []*driver.ValueExpr, err error) {
 	pr := paramReplacerPool.Get().(*paramReplacer)
 	pCtx := paramCtxPool.Get().(*format.RestoreCtx)
 	defer func() {
@@ -81,7 +82,7 @@ func ParameterizeAST(sctx sessionctx.Context, stmt ast.StmtNode) (paramSQL strin
 	}()
 	stmt.Accept(pr)
 	if err := stmt.Restore(pCtx); err != nil {
-		err = RestoreASTWithParams(sctx, stmt, pr.params)
+		err = RestoreASTWithParams(ctx, sctx, stmt, pr.params) // keep the stmt unchanged if err
 		return "", nil, err
 	}
 	paramSQL, params = pCtx.In.(*strings.Builder).String(), pr.params
@@ -119,7 +120,11 @@ func (pr *paramRestorer) Reset() {
 
 // RestoreASTWithParams restore this parameterized AST with specific parameters.
 // e.g. `select * from t where a<? and b<?`, [10, 23] --> `select * from t where a<10 and b<23`.
-func RestoreASTWithParams(_ sessionctx.Context, stmt ast.StmtNode, params []*driver.ValueExpr) error {
+func RestoreASTWithParams(ctx context.Context, _ sessionctx.Context, stmt ast.StmtNode, params []*driver.ValueExpr) error {
+	if v := ctx.Value("____RestoreASTWithParamsErr"); v != nil {
+		return errors.New("____RestoreASTWithParamsErr")
+	}
+
 	pr := paramRestorerPool.Get().(*paramRestorer)
 	defer func() {
 		pr.Reset()

planner/core/plan_cache_param_test.go

@@ -15,6 +15,7 @@
 package core
 
 import (
+	"context"
 	"strings"
 	"testing"
 
@@ -61,15 +62,15 @@ func TestParameterize(t *testing.T) {
 	for _, c := range cases {
 		stmt, err := parser.New().ParseOneStmt(c.sql, "", "")
 		require.Nil(t, err)
-		paramSQL, params, err := ParameterizeAST(sctx, stmt)
+		paramSQL, params, err := ParameterizeAST(context.Background(), sctx, stmt)
 		require.Nil(t, err)
 		require.Equal(t, c.paramSQL, paramSQL)
 		require.Equal(t, len(c.params), len(params))
 		for i := range params {
 			require.Equal(t, c.params[i], params[i].Datum.GetValue())
 		}
 
-		err = RestoreASTWithParams(sctx, stmt, params)
+		err = RestoreASTWithParams(context.Background(), sctx, stmt, params)
 		require.Nil(t, err)
 		var buf strings.Builder
 		rCtx := format.NewRestoreCtx(format.DefaultRestoreFlags, &buf)

planner/core/plan_cache_test.go

@@ -15,6 +15,7 @@
 package core_test
 
 import (
+	"context"
 	"errors"
 	"fmt"
 	"math/rand"
@@ -112,6 +113,45 @@ func TestNonPreparedPlanCacheWithExplain(t *testing.T) {
 	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("1"))
 }
 
+func TestNonPreparedPlanCacheFallback(t *testing.T) {
+	store := testkit.CreateMockStore(t)
+	tk := testkit.NewTestKit(t, store)
+	tk.MustExec(`use test`)
+	tk.MustExec(`create table t (a int)`)
+	for i := 0; i < 5; i++ {
+		tk.MustExec(fmt.Sprintf("insert into t values (%v)", i))
+	}
+	tk.MustExec("set tidb_enable_non_prepared_plan_cache=1")
+
+	// inject a fault to GeneratePlanCacheStmtWithAST
+	ctx := context.WithValue(context.Background(), "____GeneratePlanCacheStmtWithASTErr", struct{}{})
+	tk.MustQueryWithContext(ctx, "select * from t where a in (1, 2)").Sort().Check(testkit.Rows("1", "2"))
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0")) // cannot generate PlanCacheStmt
+	tk.MustQueryWithContext(ctx, "select * from t where a in (1, 3)").Sort().Check(testkit.Rows("1", "3"))
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0")) // cannot generate PlanCacheStmt
+	tk.MustQuery("select * from t where a in (1, 2)").Sort().Check(testkit.Rows("1", "2"))
+	tk.MustQuery("select * from t where a in (1, 3)").Sort().Check(testkit.Rows("1", "3"))
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("1")) // no error
+
+	// inject a fault to GetPlanFromSessionPlanCache
+	tk.MustQuery("select * from t where a=1").Check(testkit.Rows("1")) // cache this plan
+	tk.MustQuery("select * from t where a=2").Check(testkit.Rows("2")) // plan from cache
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("1"))
+	ctx = context.WithValue(context.Background(), "____GetPlanFromSessionPlanCacheErr", struct{}{})
+	tk.MustQueryWithContext(ctx, "select * from t where a=3").Check(testkit.Rows("3"))
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0")) // fallback to the normal opt-path
+	tk.MustQueryWithContext(ctx, "select * from t where a=4").Check(testkit.Rows("4"))
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0")) // fallback to the normal opt-path
+	tk.MustQueryWithContext(context.Background(), "select * from t where a=0").Check(testkit.Rows("0"))
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("1")) // use the cached plan if no error
+
+	// inject a fault to RestoreASTWithParams
+	ctx = context.WithValue(context.Background(), "____GetPlanFromSessionPlanCacheErr", struct{}{})
+	ctx = context.WithValue(ctx, "____RestoreASTWithParamsErr", struct{}{})
+	_, err := tk.ExecWithContext(ctx, "select * from t where a=1")
+	require.NotNil(t, err)
+}
+
 func TestNonPreparedPlanCacheBasically(t *testing.T) {
 	store := testkit.CreateMockStore(t)
 	tk := testkit.NewTestKit(t, store)

planner/core/plan_cache_utils.go

@@ -67,6 +67,10 @@ func (e *paramMarkerExtractor) Leave(in ast.Node) (ast.Node, bool) {
 // paramSQL is the corresponding parameterized sql like 'select * from t where a<? and b>?'.
 // paramStmt is the Node of paramSQL.
 func GeneratePlanCacheStmtWithAST(ctx context.Context, sctx sessionctx.Context, paramSQL string, paramStmt ast.StmtNode) (*PlanCacheStmt, Plan, int, error) {
+	if v := ctx.Value("____GeneratePlanCacheStmtWithASTErr"); v != nil { // for testing
+		return nil, nil, 0, errors.New("____GeneratePlanCacheStmtWithASTErr")
+	}
+
 	vars := sctx.GetSessionVars()
 	var extractor paramMarkerExtractor
 	paramStmt.Accept(&extractor)

planner/optimize.go

@@ -74,15 +74,22 @@ func matchSQLBinding(sctx sessionctx.Context, stmtNode ast.StmtNode) (bindRecord
 }
 
 // getPlanFromNonPreparedPlanCache tries to get an available cached plan from the NonPrepared Plan Cache for this stmt.
-func getPlanFromNonPreparedPlanCache(ctx context.Context, sctx sessionctx.Context, stmt ast.StmtNode, is infoschema.InfoSchema) (core.Plan, types.NameSlice, bool, error) {
+func getPlanFromNonPreparedPlanCache(ctx context.Context, sctx sessionctx.Context, stmt ast.StmtNode, is infoschema.InfoSchema) (p core.Plan, ns types.NameSlice, ok bool, err error) {
 	if sctx.GetSessionVars().StmtCtx.InPreparedPlanBuilding || // already in cached plan rebuilding phase
 		!core.NonPreparedPlanCacheableWithCtx(sctx, stmt, is) {
 		return nil, nil, false, nil
 	}
-	paramSQL, params, err := core.ParameterizeAST(sctx, stmt)
+	paramSQL, params, err := core.ParameterizeAST(ctx, sctx, stmt)
 	if err != nil {
 		return nil, nil, false, err
 	}
+	defer func() {
+		if err != nil {
+			// keep the stmt unchanged if err so that it can fallback to the normal optimization path.
+			// TODO: add metrics
+			err = core.RestoreASTWithParams(ctx, sctx, stmt, params)
+		}
+	}()
 	val := sctx.GetSessionVars().GetNonPreparedPlanCacheStmt(paramSQL)
 	if val == nil {
 		cachedStmt, _, _, err := core.GeneratePlanCacheStmtWithAST(ctx, sctx, paramSQL, stmt)