sql: move RandString to util to break coldata->rangden->sem/tree dep

Epic: CRDB-18892
Informs: cockroachdb#91831
Release note: None

pkg/col/coldata/BUILD.bazel

@@ -48,8 +48,8 @@ go_test(
     deps = [
         "//pkg/col/coldatatestutils",
         "//pkg/sql/colconv",
-        "//pkg/sql/randgen",
         "//pkg/sql/types",
+        "//pkg/util",
         "//pkg/util/leaktest",
         "//pkg/util/randutil",
         "@com_github_cockroachdb_errors//:errors",

pkg/col/coldata/bytes_test.go

@@ -18,7 +18,7 @@ import (
 	"testing"
 	"unsafe"
 
-	"github.com/cockroachdb/cockroach/pkg/sql/randgen"
+	"github.com/cockroachdb/cockroach/pkg/util"
 	"github.com/cockroachdb/cockroach/pkg/util/leaktest"
 	"github.com/cockroachdb/cockroach/pkg/util/randutil"
 	"github.com/cockroachdb/errors"
@@ -523,7 +523,7 @@ func TestArrowConversion(t *testing.T) {
 		if rng.Float64() < nullChance {
 			continue
 		}
-		element := []byte(randgen.RandString(rng, 1+rng.Intn(maxStringLength), letters))
+		element := []byte(util.RandString(rng, 1+rng.Intn(maxStringLength), letters))
 		b.Set(i, element)
 	}
 

pkg/internal/sqlsmith/BUILD.bazel

@@ -33,6 +33,7 @@ go_library(
         "//pkg/sql/sem/tree/treewindow",
         "//pkg/sql/sem/volatility",
         "//pkg/sql/types",
+        "//pkg/util",
         "//pkg/util/randident",
         "//pkg/util/randident/randidentcfg",
         "//pkg/util/syncutil",

pkg/internal/sqlsmith/relational.go

@@ -15,6 +15,7 @@ import (
 	"github.com/cockroachdb/cockroach/pkg/sql/sem/tree"
 	"github.com/cockroachdb/cockroach/pkg/sql/sem/tree/treecmp"
 	"github.com/cockroachdb/cockroach/pkg/sql/types"
+	"github.com/cockroachdb/cockroach/pkg/util"
 )
 
 func (s *Smither) makeStmt() (stmt tree.Statement, ok bool) {
@@ -1001,7 +1002,7 @@ func makeBegin(s *Smither) (tree.Statement, bool) {
 const letters = "abcdefghijklmnopqrstuvwxyz"
 
 func makeSavepoint(s *Smither) (tree.Statement, bool) {
-	savepointName := randgen.RandString(s.rnd, s.d9(), letters)
+	savepointName := util.RandString(s.rnd, s.d9(), letters)
 	s.activeSavepoints = append(s.activeSavepoints, savepointName)
 	return &tree.Savepoint{Name: tree.Name(savepointName)}, true
 }

pkg/sql/randgen/BUILD.bazel

@@ -10,7 +10,6 @@ go_library(
         "expr.go",
         "mutator.go",
         "schema.go",
-        "string.go",
         "type.go",
     ],
     importpath = "github.com/cockroachdb/cockroach/pkg/sql/randgen",
@@ -39,6 +38,7 @@ go_library(
         "//pkg/sql/sem/volatility",
         "//pkg/sql/stats",
         "//pkg/sql/types",
+        "//pkg/util",
         "//pkg/util/bitarray",
         "//pkg/util/duration",
         "//pkg/util/encoding",

pkg/sql/randgen/schema.go

@@ -27,6 +27,7 @@ import (
 	"github.com/cockroachdb/cockroach/pkg/sql/sem/eval"
 	"github.com/cockroachdb/cockroach/pkg/sql/sem/tree"
 	"github.com/cockroachdb/cockroach/pkg/sql/types"
+	"github.com/cockroachdb/cockroach/pkg/util"
 	"github.com/cockroachdb/cockroach/pkg/util/randutil"
 	"github.com/cockroachdb/errors"
 	"github.com/lib/pq/oid"
@@ -53,7 +54,7 @@ func RandCreateType(rng *rand.Rand, name, alphabet string) tree.Statement {
 	labelsMap := make(map[string]struct{})
 	i := 0
 	for i < numLabels {
-		s := RandString(rng, rng.Intn(6)+1, alphabet)
+		s := util.RandString(rng, rng.Intn(6)+1, alphabet)
 		if _, ok := labelsMap[s]; !ok {
 			labels[i] = tree.EnumValue(s)
 			labelsMap[s] = struct{}{}

pkg/sql/rowenc/BUILD.bazel

@@ -84,6 +84,7 @@ go_test(
         "//pkg/sql/types",
         "//pkg/testutils/datapathutils",
         "//pkg/testutils/serverutils",
+        "//pkg/util",
         "//pkg/util/encoding",
         "//pkg/util/json",
         "//pkg/util/leaktest",

pkg/sql/rowenc/index_encoding_test.go

@@ -33,6 +33,7 @@ import (
 	"github.com/cockroachdb/cockroach/pkg/sql/sem/eval"
 	"github.com/cockroachdb/cockroach/pkg/sql/sem/tree"
 	"github.com/cockroachdb/cockroach/pkg/sql/types"
+	"github.com/cockroachdb/cockroach/pkg/util"
 	"github.com/cockroachdb/cockroach/pkg/util/json"
 	"github.com/cockroachdb/cockroach/pkg/util/randutil"
 	"github.com/cockroachdb/cockroach/pkg/util/trigram"
@@ -1022,9 +1023,9 @@ func TestEncodeTrigramInvertedIndexSpans(t *testing.T) {
 
 		// Generate two random strings and evaluate left % right, left LIKE right,
 		// and left = right both via eval and via the span comparisons.
-		left := randgen.RandString(rng, 15, alphabet)
+		left := util.RandString(rng, 15, alphabet)
 		length := 3 + rng.Intn(5)
-		right := randgen.RandString(rng, length, alphabet+"%")
+		right := util.RandString(rng, length, alphabet+"%")
 
 		for _, searchType := range []trigramSearchType{like, eq, similar} {
 			expr := makeTrigramBinOp(t, left, right, searchType)

pkg/util/strings.go

@@ -14,6 +14,7 @@ import (
 	"bytes"
 	"fmt"
 	io "io"
+	"math/rand"
 	"strings"
 	"text/tabwriter"
 	"unicode/utf8"
@@ -156,3 +157,13 @@ func ExpandTabsInRedactableBytes(s redact.RedactableBytes) (redact.RedactableByt
 	}
 	return redact.RedactableBytes(buf.Bytes()), nil
 }
+
+// RandString generates a random string of the desired length from the
+// input alphabet.
+func RandString(rng *rand.Rand, length int, alphabet string) string {
+	buf := make([]byte, length)
+	for i := range buf {
+		buf[i] = alphabet[rng.Intn(len(alphabet))]
+	}
+	return string(buf)
+}