Implement Migration Complexity Explanation providing the summary and rationale for reported complexity

migtests/scripts/functions.sh

@@ -891,6 +891,7 @@ normalize_json() {
             .OptimalSelectConnectionsPerNode? = "IGNORED" |
             .OptimalInsertConnectionsPerNode? = "IGNORED" |
             .RowCount? = "IGNORED" |
+			.MigrationComplexityExplanation?= "IGNORED" |
             # Replace newline characters in SqlStatement with spaces
 			.SqlStatement? |= (
 				if type == "string" then

yb-voyager/cmd/assessMigrationCommand.go

@@ -425,6 +425,7 @@ func assessMigration() (err error) {
 	}
 
 	log.Infof("number of assessment issues detected: %d\n", len(assessmentReport.Issues))
+
 	utils.PrintAndLog("Migration assessment completed successfully.")
 	completedEvent := createMigrationAssessmentCompletedEvent()
 	controlPlane.MigrationAssessmentCompleted(completedEvent)
@@ -1602,6 +1603,14 @@ func postProcessingOfAssessmentReport() {
 func generateAssessmentReportJson(reportDir string) error {
 	jsonReportFilePath := filepath.Join(reportDir, fmt.Sprintf("%s%s", ASSESSMENT_FILE_NAME, JSON_EXTENSION))
 	log.Infof("writing assessment report to file: %s", jsonReportFilePath)
+
+	var err error
+	assessmentReport.MigrationComplexityExplanation, err = buildMigrationComplexityExplanation(source.DBType, assessmentReport, "")
+	if err != nil {
+		return fmt.Errorf("unable to build migration complexity explanation for json report: %w", err)
+	}
+	log.Info(assessmentReport.MigrationComplexityExplanation)
+
 	strReport, err := json.MarshalIndent(assessmentReport, "", "\t")
 	if err != nil {
 		return fmt.Errorf("failed to marshal the assessment report: %w", err)
@@ -1620,6 +1629,12 @@ func generateAssessmentReportHtml(reportDir string) error {
 	htmlReportFilePath := filepath.Join(reportDir, fmt.Sprintf("%s%s", ASSESSMENT_FILE_NAME, HTML_EXTENSION))
 	log.Infof("writing assessment report to file: %s", htmlReportFilePath)
 
+	var err error
+	assessmentReport.MigrationComplexityExplanation, err = buildMigrationComplexityExplanation(source.DBType, assessmentReport, "html")
+	if err != nil {
+		return fmt.Errorf("unable to build migration complexity explanation for html report: %w", err)
+	}
+
 	file, err := os.Create(htmlReportFilePath)
 	if err != nil {
 		return fmt.Errorf("failed to create file for %q: %w", filepath.Base(htmlReportFilePath), err)

yb-voyager/cmd/common.go

@@ -1051,14 +1051,15 @@ func storeTableListInMSR(tableList []sqlname.NameTuple) error {
 
 // TODO: consider merging all unsupported field with single AssessmentReport struct member as AssessmentIssue
 type AssessmentReport struct {
-	VoyagerVersion      string                                `json:"VoyagerVersion"`
-	TargetDBVersion     *ybversion.YBVersion                  `json:"TargetDBVersion"`
-	MigrationComplexity string                                `json:"MigrationComplexity"`
-	SchemaSummary       utils.SchemaSummary                   `json:"SchemaSummary"`
-	Sizing              *migassessment.SizingAssessmentReport `json:"Sizing"`
-	Issues              []AssessmentIssue                     `json:"-"` // disabled in reports till corresponding UI changes are done(json and html reports)
-	TableIndexStats     *[]migassessment.TableIndexStats      `json:"TableIndexStats"`
-	Notes               []string                              `json:"Notes"`
+	VoyagerVersion                 string                                `json:"VoyagerVersion"`
+	TargetDBVersion                *ybversion.YBVersion                  `json:"TargetDBVersion"`
+	MigrationComplexity            string                                `json:"MigrationComplexity"`
+	MigrationComplexityExplanation string                                `json:"MigrationComplexityExplanation"`
+	SchemaSummary                  utils.SchemaSummary                   `json:"SchemaSummary"`
+	Sizing                         *migassessment.SizingAssessmentReport `json:"Sizing"`
+	Issues                         []AssessmentIssue                     `json:"-"` // disabled in reports till corresponding UI changes are done(json and html reports)
+	TableIndexStats                *[]migassessment.TableIndexStats      `json:"TableIndexStats"`
+	Notes                          []string                              `json:"Notes"`
 
 	// fields going to be deprecated
 	UnsupportedDataTypes       []utils.TableColumnsDataTypes     `json:"UnsupportedDataTypes"`

yb-voyager/cmd/common_test.go

@@ -129,21 +129,22 @@ func TestAssessmentReportStructs(t *testing.T) {
 			name:       "Validate AssessmentReport Struct Definition",
 			actualType: reflect.TypeOf(AssessmentReport{}),
 			expectedType: struct {
-				VoyagerVersion             string                                `json:"VoyagerVersion"`
-				TargetDBVersion            *ybversion.YBVersion                  `json:"TargetDBVersion"`
-				MigrationComplexity        string                                `json:"MigrationComplexity"`
-				SchemaSummary              utils.SchemaSummary                   `json:"SchemaSummary"`
-				Sizing                     *migassessment.SizingAssessmentReport `json:"Sizing"`
-				Issues                     []AssessmentIssue                     `json:"-"`
-				TableIndexStats            *[]migassessment.TableIndexStats      `json:"TableIndexStats"`
-				Notes                      []string                              `json:"Notes"`
-				UnsupportedDataTypes       []utils.TableColumnsDataTypes         `json:"UnsupportedDataTypes"`
-				UnsupportedDataTypesDesc   string                                `json:"UnsupportedDataTypesDesc"`
-				UnsupportedFeatures        []UnsupportedFeature                  `json:"UnsupportedFeatures"`
-				UnsupportedFeaturesDesc    string                                `json:"UnsupportedFeaturesDesc"`
-				UnsupportedQueryConstructs []utils.UnsupportedQueryConstruct     `json:"UnsupportedQueryConstructs"`
-				UnsupportedPlPgSqlObjects  []UnsupportedFeature                  `json:"UnsupportedPlPgSqlObjects"`
-				MigrationCaveats           []UnsupportedFeature                  `json:"MigrationCaveats"`
+				VoyagerVersion                 string                                `json:"VoyagerVersion"`
+				TargetDBVersion                *ybversion.YBVersion                  `json:"TargetDBVersion"`
+				MigrationComplexity            string                                `json:"MigrationComplexity"`
+				MigrationComplexityExplanation string                                `json:"MigrationComplexityExplanation"`
+				SchemaSummary                  utils.SchemaSummary                   `json:"SchemaSummary"`
+				Sizing                         *migassessment.SizingAssessmentReport `json:"Sizing"`
+				Issues                         []AssessmentIssue                     `json:"-"`
+				TableIndexStats                *[]migassessment.TableIndexStats      `json:"TableIndexStats"`
+				Notes                          []string                              `json:"Notes"`
+				UnsupportedDataTypes           []utils.TableColumnsDataTypes         `json:"UnsupportedDataTypes"`
+				UnsupportedDataTypesDesc       string                                `json:"UnsupportedDataTypesDesc"`
+				UnsupportedFeatures            []UnsupportedFeature                  `json:"UnsupportedFeatures"`
+				UnsupportedFeaturesDesc        string                                `json:"UnsupportedFeaturesDesc"`
+				UnsupportedQueryConstructs     []utils.UnsupportedQueryConstruct     `json:"UnsupportedQueryConstructs"`
+				UnsupportedPlPgSqlObjects      []UnsupportedFeature                  `json:"UnsupportedPlPgSqlObjects"`
+				MigrationCaveats               []UnsupportedFeature                  `json:"MigrationCaveats"`
 			}{},
 		},
 	}
@@ -165,9 +166,10 @@ func TestAssessmentReportJson(t *testing.T) {
 	}
 
 	assessmentReport = AssessmentReport{
-		VoyagerVersion:      "v1.0.0",
-		TargetDBVersion:     newYbVersion,
-		MigrationComplexity: "High",
+		VoyagerVersion:                 "v1.0.0",
+		TargetDBVersion:                newYbVersion,
+		MigrationComplexity:            "High",
+		MigrationComplexityExplanation: "",
 		SchemaSummary: utils.SchemaSummary{
 			Description: "Test Schema Summary",
 			DBName:      "test_db",
@@ -302,12 +304,12 @@ func TestAssessmentReportJson(t *testing.T) {
 	if err != nil {
 		t.Fatalf("Failed to write assessment report to JSON file: %v", err)
 	}
-
 	// expected JSON
 	expectedJSON := `{
 	"VoyagerVersion": "v1.0.0",
 	"TargetDBVersion": "2024.1.1.1",
 	"MigrationComplexity": "High",
+	"MigrationComplexityExplanation": "",
 	"SchemaSummary": {
 		"Description": "Test Schema Summary",
 		"DbName": "test_db",

yb-voyager/cmd/migration_complexity.go

@@ -16,12 +16,14 @@ limitations under the License.
 package cmd
 
 import (
+	"bytes"
 	"encoding/csv"
 	"fmt"
 	"math"
 	"os"
 	"path/filepath"
 	"strings"
+	"text/template"
 
 	"github.com/samber/lo"
 	log "github.com/sirupsen/logrus"
@@ -33,15 +35,16 @@ import (
 const NOT_AVAILABLE = "NOT AVAILABLE"
 
 var (
-	LEVEL_1_MEDIUM_THRESHOLD = 20
-	LEVEL_1_HIGH_THRESHOLD   = math.MaxInt32
-	LEVEL_2_MEDIUM_THRESHOLD = 10
-	LEVEL_2_HIGH_THRESHOLD   = 100
-	LEVEL_3_MEDIUM_THRESHOLD = 0
-	LEVEL_3_HIGH_THRESHOLD   = 4
+	LEVEL_1_MEDIUM_THRESHOLD     = 20
+	LEVEL_1_HIGH_THRESHOLD       = math.MaxInt32
+	LEVEL_2_MEDIUM_THRESHOLD     = 10
+	LEVEL_2_HIGH_THRESHOLD       = 100
+	LEVEL_3_MEDIUM_THRESHOLD     = 0
+	LEVEL_3_HIGH_THRESHOLD       = 4
+	migrationComplexityRationale string
 )
 
-// Migration complexity calculation from the conversion issues
+// Migration complexity calculation based on the detected assessment issues
 func calculateMigrationComplexity(sourceDBType string, schemaDirectory string, assessmentReport AssessmentReport) string {
 	if sourceDBType != ORACLE && sourceDBType != POSTGRESQL {
 		return NOT_AVAILABLE
@@ -64,30 +67,37 @@ func calculateMigrationComplexity(sourceDBType string, schemaDirectory string, a
 }
 
 func calculateMigrationComplexityForPG(assessmentReport AssessmentReport) string {
+	if assessmentReport.MigrationComplexity != "" {
+		return assessmentReport.MigrationComplexity
+	}
+
 	counts := lo.CountValuesBy(assessmentReport.Issues, func(issue AssessmentIssue) string {
 		return issue.Impact
 	})
+	l1IssueCount := counts[constants.IMPACT_LEVEL_1]
+	l2IssueCount := counts[constants.IMPACT_LEVEL_2]
+	l3IssueCount := counts[constants.IMPACT_LEVEL_3]
 
-	level1IssueCount := counts[constants.IMPACT_LEVEL_1]
-	level2IssueCount := counts[constants.IMPACT_LEVEL_2]
-	level3IssueCount := counts[constants.IMPACT_LEVEL_3]
+	log.Infof("issue counts: level-1=%d, level-2=%d, level-3=%d\n", l1IssueCount, l2IssueCount, l3IssueCount)
 
-	utils.PrintAndLog("issue counts: level-1=%d, level-2=%d, level-3=%d\n", level1IssueCount, level2IssueCount, level3IssueCount)
 	// Determine complexity for each level
-	comp1 := getComplexityForLevel(constants.IMPACT_LEVEL_1, level1IssueCount)
-	comp2 := getComplexityForLevel(constants.IMPACT_LEVEL_2, level2IssueCount)
-	comp3 := getComplexityForLevel(constants.IMPACT_LEVEL_3, level3IssueCount)
+	comp1 := getComplexityForLevel(constants.IMPACT_LEVEL_1, l1IssueCount)
+	comp2 := getComplexityForLevel(constants.IMPACT_LEVEL_2, l2IssueCount)
+	comp3 := getComplexityForLevel(constants.IMPACT_LEVEL_3, l3IssueCount)
 	complexities := []string{comp1, comp2, comp3}
+	log.Infof("complexities according to each level: %v", complexities)
 
+	finalComplexity := constants.MIGRATION_COMPLEXITY_LOW
 	// If ANY level is HIGH => final is HIGH
 	if slices.Contains(complexities, constants.MIGRATION_COMPLEXITY_HIGH) {
-		return constants.MIGRATION_COMPLEXITY_HIGH
+		finalComplexity = constants.MIGRATION_COMPLEXITY_HIGH
+	} else if slices.Contains(complexities, constants.MIGRATION_COMPLEXITY_MEDIUM) {
+		// Else if ANY level is MEDIUM => final is MEDIUM
+		finalComplexity = constants.MIGRATION_COMPLEXITY_MEDIUM
 	}
-	// Else if ANY level is MEDIUM => final is MEDIUM
-	if slices.Contains(complexities, constants.MIGRATION_COMPLEXITY_MEDIUM) {
-		return constants.MIGRATION_COMPLEXITY_MEDIUM
-	}
-	return constants.MIGRATION_COMPLEXITY_LOW
+
+	migrationComplexityRationale = buildRationale(finalComplexity, l1IssueCount, l2IssueCount, l3IssueCount)
+	return finalComplexity
 }
 
 // This is a temporary logic to get migration complexity for oracle based on the migration level from ora2pg report.
@@ -200,3 +210,127 @@ func getComplexityForLevel(level string, count int) string {
 		panic(fmt.Sprintf("unknown impact level %s for determining complexity", level))
 	}
 }
+
+// ======================================= Migration Complexity Explanation ==========================================
+
+// TODO: discuss if the html should be in main report or here
+const explainTemplateHTML = `
+<p>Below is a detailed breakdown of issues by category, showing the count for each impact level.</p>
+<table border="1" cellpadding="5" cellspacing="0" style="border-collapse: collapse;">
+    <thead>
+        <tr>
+            <th>Category</th>
+            <th>Level-1</th>
+            <th>Level-2</th>
+            <th>Level-3</th>
+            <th>Total</th>
+        </tr>
+    </thead>
+    <tbody>
+    {{- range .Summaries }}
+        <tr>
+            <td>{{ .Category }}</td>
+            <td>{{ index .ImpactCounts "LEVEL_1" }}</td>
+            <td>{{ index .ImpactCounts "LEVEL_2" }}</td>
+            <td>{{ index .ImpactCounts "LEVEL_3" }}</td>
+            <td>{{ .TotalIssueCount }}</td>
+        </tr>
+    {{- end }}
+    </tbody>
+</table>
+
+<p>
+	<strong>Complexity:</strong> {{ .Complexity }}</br>
+	<strong>Reasoning:</strong> {{ .ComplexityRationale }}
+</p>
+
+<p>
+<strong>Impact Levels:</strong></br>
+	Level-1: Resolutions are available with minimal effort.<br/>
+	Level-2: Resolutions are available requiring moderate effort.<br/>
+	Level-3: Resolutions may not be available or are complex.
+</p>
+`
+
+const explainTemplateText = `Reasoning: {{ .ComplexityRationale }}`
+
+type MigrationComplexityExplanationData struct {
+	Summaries           []MigrationComplexityCategorySummary
+	Complexity          string
+	ComplexityRationale string // short reasoning or explanation text
+}
+
+type MigrationComplexityCategorySummary struct {
+	Category        string
+	TotalIssueCount int
+	ImpactCounts    map[string]int // e.g. {"Level-1": 3, "Level-2": 5, "Level-3": 2}
+}
+
+func buildMigrationComplexityExplanation(sourceDBType string, assessmentReport AssessmentReport, reportFormat string) (string, error) {
+	if sourceDBType != POSTGRESQL {
+		return "", nil
+	}
+
+	var explanation MigrationComplexityExplanationData
+	explanation.Complexity = assessmentReport.MigrationComplexity
+	explanation.ComplexityRationale = migrationComplexityRationale
+
+	explanation.Summaries = buildCategorySummary(assessmentReport.Issues)
+
+	var tmpl *template.Template
+	var err error
+	if reportFormat == "html" {
+		tmpl, err = template.New("Explain").Parse(explainTemplateHTML)
+	} else {
+		tmpl, err = template.New("Explain").Parse(explainTemplateText)
+	}
+
+	if err != nil {
+		return "", fmt.Errorf("failed creating the explanation template: %w", err)
+	}
+
+	var buf bytes.Buffer
+	if err := tmpl.Execute(&buf, explanation); err != nil {
+		return "", fmt.Errorf("failed executing the template with data: %w", err)
+	}
+	return buf.String(), nil
+}
+
+func buildRationale(finalComplexity string, l1Count int, l2Count int, l3Count int) string {
+	switch finalComplexity {
+	case constants.MIGRATION_COMPLEXITY_HIGH:
+		return fmt.Sprintf("Found %d Level-2 issue(s) and %d Level-3 issue(s), resulting in HIGH migration complexity", l2Count, l3Count)
+	case constants.MIGRATION_COMPLEXITY_MEDIUM:
+		return fmt.Sprintf("Found %d Level-1 issue(s), %d Level-2 issue(s) and %d Level-3 issue(s), resulting in MEDIUM migration complexity", l1Count, l2Count, l3Count)
+	case constants.MIGRATION_COMPLEXITY_LOW:
+		return fmt.Sprintf("Found %d Level-1 issue(s) and %d Level-2 issue(s), resulting in LOW migration complexity", l1Count, l2Count)
+	}
+	return ""
+}
+
+func buildCategorySummary(issues []AssessmentIssue) []MigrationComplexityCategorySummary {
+	summaryMap := make(map[string]*MigrationComplexityCategorySummary)
+	for _, issue := range issues {
+		if issue.Category == "" {
+			continue // skipping unknown category issues
+		}
+
+		if _, ok := summaryMap[issue.Category]; !ok {
+			summaryMap[issue.Category] = &MigrationComplexityCategorySummary{
+				Category:        issue.Category,
+				TotalIssueCount: 0,
+				ImpactCounts:    make(map[string]int),
+			}
+		}
+
+		summaryMap[issue.Category].TotalIssueCount++
+		summaryMap[issue.Category].ImpactCounts[issue.Impact]++
+	}
+
+	var result []MigrationComplexityCategorySummary
+	for _, summary := range summaryMap {
+		summary.Category = utils.SnakeCaseToTitleCase(summary.Category)
+		result = append(result, *summary)
+	}
+	return result
+}

yb-voyager/cmd/templates/migration_assessment_report.template

@@ -167,6 +167,11 @@
             {{ end }}
         {{end}}
 
+        {{if ne .MigrationComplexity "NOT AVAILABLE"}}
+            <h2>Migration Complexity Explanation</h2>
+            <p>{{ .MigrationComplexityExplanation }}</p>
+        {{end}}
+
         <h2>Unsupported Data Types</h2>
         <p>{{.UnsupportedDataTypesDesc}}</p>
         {{ if .UnsupportedDataTypes }}

yb-voyager/src/utils/utils.go

@@ -38,6 +38,8 @@ import (
 	"github.com/samber/lo"
 	log "github.com/sirupsen/logrus"
 	"golang.org/x/exp/slices"
+	"golang.org/x/text/cases"
+	"golang.org/x/text/language"
 )
 
 var DoNotPrompt bool
@@ -744,3 +746,14 @@ func CheckTools(tools ...string) []string {
 func BuildObjectName(schemaName, objName string) string {
 	return lo.Ternary(schemaName != "", schemaName+"."+objName, objName)
 }
+
+// SnakeCaseToTitleCase converts a snake_case string to a title case string with spaces.
+func SnakeCaseToTitleCase(snake string) string {
+	words := strings.Split(snake, "_")
+	c := cases.Title(language.English)
+	for i, word := range words {
+		words[i] = c.String(word)
+	}
+
+	return strings.Join(words, " ")
+}