opt: set all session settings to their global default

All session settings in optimizer tests and benchmarks are now set to
their global defaults. Prior to this commit each new session setting had
to be manually set in both tests and benchmarks. This step could be
forgotten, such as with `optimizer_merge_joins_enabled` which was
unknowingly disabled in benchmarks when it was added. Now, all session
settings with global defaults are automatically set.

Additionally, `sql.SetSessionVariable` has been renamed to
`sql.TestingSetSessionVariable` to discourage its use outside of tests.

NOTE: Now that `optimizer_merge_joins_enabled` is enabled, some
benchmarks will appear to regress.

Release note: None

pkg/sql/opt/bench/BUILD.bazel

@@ -24,9 +24,8 @@ go_test(
         "//pkg/security/securitytest",
         "//pkg/server",
         "//pkg/settings/cluster",
+        "//pkg/sql",
         "//pkg/sql/catalog/schemaexpr",
-        "//pkg/sql/catalog/tabledesc",
-        "//pkg/sql/opt",
         "//pkg/sql/opt/exec",
         "//pkg/sql/opt/exec/execbuilder",
         "//pkg/sql/opt/exec/explain",
@@ -44,5 +43,6 @@ go_test(
         "//pkg/testutils/sqlutils",
         "//pkg/util/log",
         "//pkg/util/randutil",
+        "@com_github_cockroachdb_errors//:errors",
     ],
 )

pkg/sql/opt/bench/bench_test.go

@@ -23,9 +23,8 @@ import (
 	"github.com/cockroachdb/cockroach/pkg/security/securitytest"
 	"github.com/cockroachdb/cockroach/pkg/server"
 	"github.com/cockroachdb/cockroach/pkg/settings/cluster"
+	"github.com/cockroachdb/cockroach/pkg/sql"
 	"github.com/cockroachdb/cockroach/pkg/sql/catalog/schemaexpr"
-	"github.com/cockroachdb/cockroach/pkg/sql/catalog/tabledesc"
-	"github.com/cockroachdb/cockroach/pkg/sql/opt"
 	"github.com/cockroachdb/cockroach/pkg/sql/opt/exec"
 	"github.com/cockroachdb/cockroach/pkg/sql/opt/exec/execbuilder"
 	"github.com/cockroachdb/cockroach/pkg/sql/opt/exec/explain"
@@ -43,6 +42,7 @@ import (
 	"github.com/cockroachdb/cockroach/pkg/testutils/sqlutils"
 	"github.com/cockroachdb/cockroach/pkg/util/log"
 	"github.com/cockroachdb/cockroach/pkg/util/randutil"
+	"github.com/cockroachdb/errors"
 )
 
 // A query can be issued using the "simple protocol" or the "prepare protocol".
@@ -754,25 +754,10 @@ func newHarness(tb testing.TB, query benchQuery, schemas []string) *harness {
 		evalCtx: eval.MakeTestingEvalContext(cluster.MakeTestingClusterSettings()),
 	}
 
-	// Setup the default session settings.
-	h.evalCtx.SessionData().OptimizerUseMultiColStats = true
-	h.evalCtx.SessionData().ZigzagJoinEnabled = true
-	h.evalCtx.SessionData().OptimizerUseForecasts = true
-	h.evalCtx.SessionData().OptimizerUseHistograms = true
-	h.evalCtx.SessionData().LocalityOptimizedSearch = true
-	h.evalCtx.SessionData().ReorderJoinsLimit = opt.DefaultJoinOrderLimit
-	h.evalCtx.SessionData().InsertFastPath = true
-	h.evalCtx.SessionData().OptSplitScanLimit = tabledesc.MaxBucketAllowed
-	h.evalCtx.SessionData().VariableInequalityLookupJoinEnabled = true
-	h.evalCtx.SessionData().OptimizerUseVirtualComputedColumnStats = true
-	h.evalCtx.SessionData().OptimizerUseTrigramSimilarityOptimization = true
-	h.evalCtx.SessionData().OptimizerUseImprovedDistinctOnLimitHintCosting = true
-	h.evalCtx.SessionData().OptimizerUseImprovedTrigramSimilaritySelectivity = true
-	h.evalCtx.SessionData().TrigramSimilarityThreshold = 0.3
-	h.evalCtx.SessionData().OptimizerUseImprovedZigzagJoinCosting = true
-	h.evalCtx.SessionData().OptimizerUseImprovedMultiColumnSelectivityEstimate = true
-	h.evalCtx.SessionData().OptimizerProveImplicationWithVirtualComputedColumns = true
-	h.evalCtx.SessionData().OptimizerPushOffsetIntoIndexJoin = true
+	// Set session settings to their global defaults.
+	if err := sql.TestingResetSessionVariables(h.ctx, h.evalCtx); err != nil {
+		panic(errors.Wrap(err, "could not reset session variables"))
+	}
 
 	// Set up the test catalog.
 	h.testCat = testcat.New()

pkg/sql/opt/testutils/opttester/BUILD.bazel

@@ -26,7 +26,6 @@ go_library(
         "//pkg/sql",
         "//pkg/sql/catalog/descpb",
         "//pkg/sql/catalog/schemaexpr",
-        "//pkg/sql/catalog/tabledesc",
         "//pkg/sql/opt",
         "//pkg/sql/opt/cat",
         "//pkg/sql/opt/exec",

pkg/sql/opt/testutils/opttester/opt_tester.go

@@ -42,7 +42,6 @@ import (
 	"github.com/cockroachdb/cockroach/pkg/sql"
 	"github.com/cockroachdb/cockroach/pkg/sql/catalog/descpb"
 	"github.com/cockroachdb/cockroach/pkg/sql/catalog/schemaexpr"
-	"github.com/cockroachdb/cockroach/pkg/sql/catalog/tabledesc"
 	"github.com/cockroachdb/cockroach/pkg/sql/opt"
 	"github.com/cockroachdb/cockroach/pkg/sql/opt/cat"
 	"github.com/cockroachdb/cockroach/pkg/sql/opt/exec"
@@ -271,57 +270,34 @@ type Flags struct {
 
 // New constructs a new instance of the OptTester for the given SQL statement.
 // Metadata used by the SQL query is accessed via the catalog.
-func New(catalog cat.Catalog, sql string) *OptTester {
+func New(catalog cat.Catalog, sqlStr string) *OptTester {
 	ctx := context.Background()
 	ot := &OptTester{
 		catalog: catalog,
-		sql:     sql,
+		sql:     sqlStr,
 		ctx:     ctx,
 		semaCtx: tree.MakeSemaContext(catalog),
 		evalCtx: eval.MakeTestingEvalContext(cluster.MakeTestingClusterSettings()),
 	}
 	ot.f = &norm.Factory{}
 	ot.f.Init(ot.ctx, &ot.evalCtx, ot.catalog)
-	ot.evalCtx.SessionData().ReorderJoinsLimit = opt.DefaultJoinOrderLimit
-	ot.evalCtx.SessionData().OptimizerUseMultiColStats = true
 	ot.Flags.ctx = ot.ctx
 	ot.Flags.evalCtx = ot.evalCtx
 	ot.semaCtx.SearchPath = tree.EmptySearchPath
 	// To allow opttester tests to use now(), we hardcode a preset transaction
 	// time. May 10, 2017 is a historic day: the release date of CockroachDB 1.0.
 	ot.evalCtx.TxnTimestamp = time.Date(2017, 05, 10, 13, 0, 0, 0, time.UTC)
 
-	// Set any OptTester-wide session flags here.
+	// Set session settings to their global defaults.
+	if err := sql.TestingResetSessionVariables(ctx, ot.evalCtx); err != nil {
+		panic(errors.Wrap(err, "could not reset session variables"))
+	}
 
+	// Set non-default session settings.
 	ot.evalCtx.SessionData().UserProto = username.MakeSQLUsernameFromPreNormalizedString("opttester").EncodeProto()
 	ot.evalCtx.SessionData().Database = "defaultdb"
 	ot.evalCtx.SessionData().ZigzagJoinEnabled = true
-	ot.evalCtx.SessionData().OptimizerUseForecasts = true
-	ot.evalCtx.SessionData().OptimizerUseHistograms = true
-	ot.evalCtx.SessionData().LocalityOptimizedSearch = true
-	ot.evalCtx.SessionData().ReorderJoinsLimit = opt.DefaultJoinOrderLimit
-	ot.evalCtx.SessionData().InsertFastPath = true
-	ot.evalCtx.SessionData().OptSplitScanLimit = tabledesc.MaxBucketAllowed
-	ot.evalCtx.SessionData().VariableInequalityLookupJoinEnabled = true
-	ot.evalCtx.SessionData().OptimizerUseImprovedDisjunctionStats = true
-	ot.evalCtx.SessionData().OptimizerUseLimitOrderingForStreamingGroupBy = true
-	ot.evalCtx.SessionData().OptimizerUseImprovedSplitDisjunctionForJoins = true
-	ot.evalCtx.SessionData().OptimizerAlwaysUseHistograms = true
-	ot.evalCtx.SessionData().OptimizerHoistUncorrelatedEqualitySubqueries = true
-	ot.evalCtx.SessionData().OptimizerUseImprovedComputedColumnFiltersDerivation = true
-	ot.evalCtx.SessionData().OptimizerUseImprovedJoinElimination = true
-	ot.evalCtx.SessionData().OptimizerUseProvidedOrderingFix = true
-	ot.evalCtx.SessionData().OptimizerMergeJoinsEnabled = true
-	ot.evalCtx.SessionData().OptimizerUseVirtualComputedColumnStats = true
-	ot.evalCtx.SessionData().OptimizerUseTrigramSimilarityOptimization = true
-	ot.evalCtx.SessionData().OptimizerUseImprovedDistinctOnLimitHintCosting = true
-	ot.evalCtx.SessionData().OptimizerUseImprovedTrigramSimilaritySelectivity = true
-	ot.evalCtx.SessionData().TrigramSimilarityThreshold = 0.3
-	ot.evalCtx.SessionData().OptimizerUseImprovedZigzagJoinCosting = true
-	ot.evalCtx.SessionData().OptimizerUseImprovedMultiColumnSelectivityEstimate = true
-	ot.evalCtx.SessionData().OptimizerProveImplicationWithVirtualComputedColumns = true
-	ot.evalCtx.SessionData().OptimizerPushOffsetIntoIndexJoin = true
-	ot.evalCtx.SessionData().OptimizerUsePolymorphicParameterFix = true
+	ot.evalCtx.SessionData().ImplicitSelectForUpdate = false
 
 	return ot
 }
@@ -979,7 +955,7 @@ func (f *Flags) Set(arg datadriven.CmdArg) error {
 			if len(s) != 2 {
 				return errors.Errorf("Expected both session variable name and value for set flag")
 			}
-			err := sql.SetSessionVariable(f.ctx, f.evalCtx, s[0], s[1])
+			err := sql.TestingSetSessionVariable(f.ctx, f.evalCtx, s[0], s[1])
 			if err != nil {
 				return err
 			}

pkg/sql/vars.go

@@ -3534,19 +3534,18 @@ func init() {
 	}()
 }
 
-// SetSessionVariable sets a new value for session setting `varName` in the
+// TestingSetSessionVariable sets a new value for session setting `varName` in the
 // session settings owned by `evalCtx`, returning an error if not successful.
 // This function should only be used for testing. For general-purpose code,
 // please use SessionAccessor.SetSessionVar instead.
-func SetSessionVariable(
+func TestingSetSessionVariable(
 	ctx context.Context, evalCtx eval.Context, varName, varValue string,
 ) (err error) {
 	err = CheckSessionVariableValueValid(ctx, evalCtx.Settings, varName, varValue)
 	if err != nil {
 		return err
 	}
 	sdMutatorBase := sessionDataMutatorBase{
-		defaults: make(map[string]string),
 		settings: evalCtx.Settings,
 	}
 	sdMutator := sessionDataMutator{
@@ -3562,6 +3561,28 @@ func SetSessionVariable(
 	return sVar.Set(ctx, sdMutator, varValue)
 }
 
+// TestingResetSessionVariables resets all session settings in evalCtx to their
+// global default, if they have a global default.
+func TestingResetSessionVariables(ctx context.Context, evalCtx eval.Context) (err error) {
+	sdMutatorBase := sessionDataMutatorBase{
+		settings: evalCtx.Settings,
+	}
+	sdMutator := sessionDataMutator{
+		data:                        evalCtx.SessionData(),
+		sessionDataMutatorBase:      sdMutatorBase,
+		sessionDataMutatorCallbacks: sessionDataMutatorCallbacks{},
+	}
+	for _, v := range varGen {
+		if v.Set == nil || v.GlobalDefault == nil {
+			continue
+		}
+		if err := v.Set(ctx, sdMutator, v.GlobalDefault(&evalCtx.Settings.SV)); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
 // makePostgresBoolGetStringValFn returns a function that evaluates and returns
 // a string representation of the first argument value.
 func makePostgresBoolGetStringValFn(varName string) getStringValFn {