Support a complete ALTER TABLE statement in --alter

Author: shlomi-noach

go/cmd/gh-ost/main.go

@@ -14,6 +14,7 @@ import (
 
 	"github.com/github/gh-ost/go/base"
 	"github.com/github/gh-ost/go/logic"
+	"github.com/github/gh-ost/go/sql"
 	_ "github.com/go-sql-driver/mysql"
 	"github.com/outbrain/golib/log"
 
@@ -172,14 +173,24 @@ func main() {
 		log.SetLevel(log.ERROR)
 	}
 
+	if migrationContext.AlterStatement == "" {
+		log.Fatalf("--alter must be provided and statement must not be empty")
+	}
+	parser := sql.NewParserFromAlterStatement(migrationContext.AlterStatement)
+
 	if migrationContext.DatabaseName == "" {
-		log.Fatalf("--database must be provided and database name must not be empty")
+		if parser.HasExplicitSchema() {
+			migrationContext.DatabaseName = parser.GetExplicitSchema()
+		} else {
+			log.Fatalf("--database must be provided and database name must not be empty, or --alter must specify database name")
+		}
 	}
 	if migrationContext.OriginalTableName == "" {
-		log.Fatalf("--table must be provided and table name must not be empty")
-	}
-	if migrationContext.AlterStatement == "" {
-		log.Fatalf("--alter must be provided and statement must not be empty")
+		if parser.HasExplicitTable() {
+			migrationContext.OriginalTableName = parser.GetExplicitTable()
+		} else {
+			log.Fatalf("--table must be provided and table name must not be empty, or --alter must specify table name")
+		}
 	}
 	migrationContext.Noop = !(*executeFlag)
 	if migrationContext.AllowedRunningOnMaster && migrationContext.TestOnReplica {

go/logic/migrator.go

@@ -62,7 +62,7 @@ const (
 
 // Migrator is the main schema migration flow manager.
 type Migrator struct {
-	parser           *sql.Parser
+	parser           *sql.AlterTableParser
 	inspector        *Inspector
 	applier          *Applier
 	eventsStreamer   *EventsStreamer
@@ -90,7 +90,7 @@ type Migrator struct {
 func NewMigrator(context *base.MigrationContext) *Migrator {
 	migrator := &Migrator{
 		migrationContext:           context,
-		parser:                     sql.NewParser(),
+		parser:                     sql.NewAlterTableParser(),
 		ghostTableMigrated:         make(chan bool),
 		firstThrottlingCollected:   make(chan bool, 3),
 		rowCopyComplete:            make(chan error),

go/sql/parser.go

@@ -12,26 +12,47 @@ import (
 )
 
 var (
-	sanitizeQuotesRegexp = regexp.MustCompile("('[^']*')")
-	renameColumnRegexp   = regexp.MustCompile(`(?i)\bchange\s+(column\s+|)([\S]+)\s+([\S]+)\s+`)
-	dropColumnRegexp     = regexp.MustCompile(`(?i)\bdrop\s+(column\s+|)([\S]+)$`)
-	renameTableRegexp    = regexp.MustCompile(`(?i)\brename\s+(to|as)\s+`)
+	sanitizeQuotesRegexp                 = regexp.MustCompile("('[^']*')")
+	renameColumnRegexp                   = regexp.MustCompile(`(?i)\bchange\s+(column\s+|)([\S]+)\s+([\S]+)\s+`)
+	dropColumnRegexp                     = regexp.MustCompile(`(?i)\bdrop\s+(column\s+|)([\S]+)$`)
+	renameTableRegexp                    = regexp.MustCompile(`(?i)\brename\s+(to|as)\s+`)
+	alterTableExplicitSchemaTableRegexps = []*regexp.Regexp{
+		regexp.MustCompile(`(?i)\balter\s+table\s+` + "`" + `([^` + "`" + `]+)` + "`" + `[.]` + "`" + `([^` + "`" + `]+)` + "`" + `\s+(.*$)`),
+		regexp.MustCompile(`(?i)\balter\s+table\s+` + "`" + `([^` + "`" + `]+)` + "`" + `[.]([\S]+)\s+(.*$)`),
+		regexp.MustCompile(`(?i)\balter\s+table\s+([\S]+)[.]` + "`" + `([^` + "`" + `]+)` + "`" + `\s+(.*$)`),
+		regexp.MustCompile(`(?i)\balter\s+table\s+([\S]+)[.]([\S]+)\s+(.*$)`),
+	}
+	alterTableExplicitTableRegexps = []*regexp.Regexp{
+		regexp.MustCompile(`(?i)\balter\s+table\s+` + "`" + `([^` + "`" + `]+)` + "`" + `\s+(.*$)`),
+		regexp.MustCompile(`(?i)\balter\s+table\s+([\S]+)\s+(.*$)`),
+	}
 )
 
-type Parser struct {
+type AlterTableParser struct {
 	columnRenameMap map[string]string
 	droppedColumns  map[string]bool
 	isRenameTable   bool
+
+	alterTokens []string
+
+	explicitSchema string
+	explicitTable  string
 }
 
-func NewParser() *Parser {
-	return &Parser{
+func NewAlterTableParser() *AlterTableParser {
+	return &AlterTableParser{
 		columnRenameMap: make(map[string]string),
 		droppedColumns:  make(map[string]bool),
 	}
 }
 
-func (this *Parser) tokenizeAlterStatement(alterStatement string) (tokens []string, err error) {
+func NewParserFromAlterStatement(alterStatement string) *AlterTableParser {
+	parser := NewAlterTableParser()
+	parser.ParseAlterStatement(alterStatement)
+	return parser
+}
+
+func (this *AlterTableParser) tokenizeAlterStatement(alterStatement string) (tokens []string, err error) {
 	terminatingQuote := rune(0)
 	f := func(c rune) bool {
 		switch {
@@ -58,13 +79,13 @@ func (this *Parser) tokenizeAlterStatement(alterStatement string) (tokens []stri
 	return tokens, nil
 }
 
-func (this *Parser) sanitizeQuotesFromAlterStatement(alterStatement string) (strippedStatement string) {
+func (this *AlterTableParser) sanitizeQuotesFromAlterStatement(alterStatement string) (strippedStatement string) {
 	strippedStatement = alterStatement
 	strippedStatement = sanitizeQuotesRegexp.ReplaceAllString(strippedStatement, "''")
 	return strippedStatement
 }
 
-func (this *Parser) parseAlterToken(alterToken string) (err error) {
+func (this *AlterTableParser) parseAlterToken(alterToken string) (err error) {
 	{
 		// rename
 		allStringSubmatch := renameColumnRegexp.FindAllStringSubmatch(alterToken, -1)
@@ -97,16 +118,33 @@ func (this *Parser) parseAlterToken(alterToken string) (err error) {
 	return nil
 }
 
-func (this *Parser) ParseAlterStatement(alterStatement string) (err error) {
+func (this *AlterTableParser) ParseAlterStatement(alterStatement string) (err error) {
+
+	for _, alterTableRegexp := range alterTableExplicitSchemaTableRegexps {
+		if submatch := alterTableRegexp.FindStringSubmatch(alterStatement); len(submatch) > 0 {
+			this.explicitSchema = submatch[1]
+			this.explicitTable = submatch[2]
+			alterStatement = submatch[3]
+			break
+		}
+	}
+	for _, alterTableRegexp := range alterTableExplicitTableRegexps {
+		if submatch := alterTableRegexp.FindStringSubmatch(alterStatement); len(submatch) > 0 {
+			this.explicitTable = submatch[1]
+			alterStatement = submatch[2]
+			break
+		}
+	}
 	alterTokens, _ := this.tokenizeAlterStatement(alterStatement)
 	for _, alterToken := range alterTokens {
 		alterToken = this.sanitizeQuotesFromAlterStatement(alterToken)
 		this.parseAlterToken(alterToken)
+		this.alterTokens = append(this.alterTokens, alterToken)
 	}
 	return nil
 }
 
-func (this *Parser) GetNonTrivialRenames() map[string]string {
+func (this *AlterTableParser) GetNonTrivialRenames() map[string]string {
 	result := make(map[string]string)
 	for column, renamed := range this.columnRenameMap {
 		if column != renamed {
@@ -116,14 +154,29 @@ func (this *Parser) GetNonTrivialRenames() map[string]string {
 	return result
 }
 
-func (this *Parser) HasNonTrivialRenames() bool {
+func (this *AlterTableParser) HasNonTrivialRenames() bool {
 	return len(this.GetNonTrivialRenames()) > 0
 }
 
-func (this *Parser) DroppedColumnsMap() map[string]bool {
+func (this *AlterTableParser) DroppedColumnsMap() map[string]bool {
 	return this.droppedColumns
 }
 
-func (this *Parser) IsRenameTable() bool {
+func (this *AlterTableParser) IsRenameTable() bool {
 	return this.isRenameTable
 }
+func (this *AlterTableParser) GetExplicitSchema() string {
+	return this.explicitSchema
+}
+
+func (this *AlterTableParser) HasExplicitSchema() bool {
+	return this.GetExplicitSchema() != ""
+}
+
+func (this *AlterTableParser) GetExplicitTable() string {
+	return this.explicitTable
+}
+
+func (this *AlterTableParser) HasExplicitTable() bool {
+	return this.GetExplicitTable() != ""
+}