Add new SQL parser to support S3 Select syntax (#7102)

- New parser written from scratch, allows easier and complete parsing
  of the full S3 Select SQL syntax. Parser definition is directly
  provided by the AST defined for the SQL grammar.

- Bring support to parse and interpret SQL involving JSON path
  expressions; evaluation of JSON path expressions will be
  subsequently added.

- Bring automatic type inference and conversion for untyped
  values (e.g. CSV data).

pkg/s3select/sql/stringfuncs_test.go

@@ -0,0 +1,107 @@
+/*
+ * Minio Cloud Storage, (C) 2019 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package sql
+
+import (
+	"testing"
+)
+
+func TestEvalSQLLike(t *testing.T) {
+	dropCases := []struct {
+		input, resultExpected string
+		matchExpected         bool
+	}{
+		{"", "", false},
+		{"a", "", true},
+		{"ab", "b", true},
+		{"தமிழ்", "மிழ்", true},
+	}
+
+	for i, tc := range dropCases {
+		res, ok := dropRune(tc.input)
+		if res != tc.resultExpected || ok != tc.matchExpected {
+			t.Errorf("DropRune Case %d failed", i)
+		}
+	}
+
+	matcherCases := []struct {
+		iText, iPat        string
+		iHasLeadingPercent bool
+		resultExpected     string
+		matchExpected      bool
+	}{
+		{"abcd", "bcd", false, "", false},
+		{"abcd", "bcd", true, "", true},
+		{"abcd", "abcd", false, "", true},
+		{"abcd", "abcd", true, "", true},
+		{"abcd", "ab", false, "cd", true},
+		{"abcd", "ab", true, "cd", true},
+		{"abcd", "bc", false, "", false},
+		{"abcd", "bc", true, "d", true},
+	}
+
+	for i, tc := range matcherCases {
+		res, ok := matcher(tc.iText, tc.iPat, tc.iHasLeadingPercent)
+		if res != tc.resultExpected || ok != tc.matchExpected {
+			t.Errorf("Matcher Case %d failed", i)
+		}
+	}
+
+	evalCases := []struct {
+		iText, iPat   string
+		iEsc          rune
+		matchExpected bool
+		errExpected   error
+	}{
+		{"abcd", "abc", runeZero, false, nil},
+		{"abcd", "abcd", runeZero, true, nil},
+		{"abcd", "abc_", runeZero, true, nil},
+		{"abcd", "_bdd", runeZero, false, nil},
+		{"abcd", "_b_d", runeZero, true, nil},
+
+		{"abcd", "____", runeZero, true, nil},
+		{"abcd", "____%", runeZero, true, nil},
+		{"abcd", "%____", runeZero, true, nil},
+		{"abcd", "%__", runeZero, true, nil},
+		{"abcd", "____", runeZero, true, nil},
+
+		{"", "_", runeZero, false, nil},
+		{"", "%", runeZero, true, nil},
+		{"abcd", "%%%%%", runeZero, true, nil},
+		{"abcd", "_____", runeZero, false, nil},
+		{"abcd", "%%%%%", runeZero, true, nil},
+
+		{"a%%d", `a\%\%d`, '\\', true, nil},
+		{"a%%d", `a\%d`, '\\', false, nil},
+		{`a%%\d`, `a\%\%\\d`, '\\', true, nil},
+		{`a%%\`, `a\%\%\\`, '\\', true, nil},
+		{`a%__%\`, `a\%\_\_\%\\`, '\\', true, nil},
+
+		{`a%__%\`, `a\%\_\_\%_`, '\\', true, nil},
+		{`a%__%\`, `a\%\_\__`, '\\', false, nil},
+		{`a%__%\`, `a\%\_\_%`, '\\', true, nil},
+		{`a%__%\`, `a?%?_?_?%\`, '?', true, nil},
+	}
+
+	for i, tc := range evalCases {
+		// fmt.Println("Case:", i)
+		res, err := evalSQLLike(tc.iText, tc.iPat, tc.iEsc)
+		if res != tc.matchExpected || err != tc.errExpected {
+			t.Errorf("Eval Case %d failed: %v %v", i, res, err)
+		}
+	}
+}