support datestyle parameter use

go.mod

@@ -9,8 +9,7 @@ require (
 	github.com/dolthub/dolt/go v0.40.5-0.20250916084833-f121f4db6fdd
 	github.com/dolthub/eventsapi_schema v0.0.0-20250915094920-eadfd39051ca
 	github.com/dolthub/flatbuffers/v23 v23.3.3-dh.2
-	github.com/dolthub/go-icu-regex v0.0.0-20250916051405-78a38d478790
-	github.com/dolthub/go-mysql-server v0.20.1-0.20250916073142-59b34ad42ad7
+	github.com/dolthub/go-mysql-server v0.20.1-0.20250916214234-32c0ab73f498
 	github.com/dolthub/sqllogictest/go v0.0.0-20240618184124-ca47f9354216
 	github.com/dolthub/vitess v0.0.0-20250915221346-753c44800850
 	github.com/fatih/color v1.13.0
@@ -99,6 +98,7 @@ require (
 	github.com/dolthub/aws-sdk-go-ini-parser v0.0.0-20250305001723-2821c37f6c12 // indirect
 	github.com/dolthub/dolt-mcp v0.2.1-0.20250827202412-9d0f6e658fba // indirect
 	github.com/dolthub/fslock v0.0.3 // indirect
+	github.com/dolthub/go-icu-regex v0.0.0-20250916051405-78a38d478790 // indirect
 	github.com/dolthub/gozstd v0.0.0-20240423170813-23a2903bca63 // indirect
 	github.com/dolthub/ishell v0.0.0-20240701202509-2b217167d718 // indirect
 	github.com/dolthub/jsonpath v0.0.2-0.20240227200619-19675ab05c71 // indirect

go.sum

@@ -258,8 +258,8 @@ github.com/dolthub/fslock v0.0.3 h1:iLMpUIvJKMKm92+N1fmHVdxJP5NdyDK5bK7z7Ba2s2U=
 github.com/dolthub/fslock v0.0.3/go.mod h1:QWql+P17oAAMLnL4HGB5tiovtDuAjdDTPbuqx7bYfa0=
 github.com/dolthub/go-icu-regex v0.0.0-20250916051405-78a38d478790 h1:zxMsH7RLiG+dlZ/y0LgJHTV26XoiSJcuWq+em6t6VVc=
 github.com/dolthub/go-icu-regex v0.0.0-20250916051405-78a38d478790/go.mod h1:F3cnm+vMRK1HaU6+rNqQrOCyR03HHhR1GWG2gnPOqaE=
-github.com/dolthub/go-mysql-server v0.20.1-0.20250916073142-59b34ad42ad7 h1:VgmY6t806cVmFRZ5YcE5awJ8YW2opk1roQhjm5Bx260=
-github.com/dolthub/go-mysql-server v0.20.1-0.20250916073142-59b34ad42ad7/go.mod h1:fkgI5RU7ABC5gknW+5Q6LUMv12Y2zlkXuDQX7n7su88=
+github.com/dolthub/go-mysql-server v0.20.1-0.20250916214234-32c0ab73f498 h1:XaYtlmLwSa6PwWzKQBvXi8TVIEaOsRyryAq17tT48fQ=
+github.com/dolthub/go-mysql-server v0.20.1-0.20250916214234-32c0ab73f498/go.mod h1:fkgI5RU7ABC5gknW+5Q6LUMv12Y2zlkXuDQX7n7su88=
 github.com/dolthub/gozstd v0.0.0-20240423170813-23a2903bca63 h1:OAsXLAPL4du6tfbBgK0xXHZkOlos63RdKYS3Sgw/dfI=
 github.com/dolthub/gozstd v0.0.0-20240423170813-23a2903bca63/go.mod h1:lV7lUeuDhH5thVGDCKXbatwKy2KW80L4rMT46n+Y2/Q=
 github.com/dolthub/ishell v0.0.0-20240701202509-2b217167d718 h1:lT7hE5k+0nkBdj/1UOSFwjWpNxf+LCApbRHgnCA17XE=

server/cast/timestamp.go

@@ -44,7 +44,7 @@ func timestampAssignment() {
 		FromType: pgtypes.Timestamp,
 		ToType:   pgtypes.Time,
 		Function: func(ctx *sql.Context, val any, targetType *pgtypes.DoltgresType) (any, error) {
-			return timeofday.FromTime(val.(time.Time)), nil
+			return timeofday.FromTime(val.(time.Time)).ToTime(), nil
 		},
 	})
 }

server/cast/timestamptz.go

@@ -44,7 +44,7 @@ func timestampTZAssignment() {
 		FromType: pgtypes.TimestampTZ,
 		ToType:   pgtypes.Time,
 		Function: func(ctx *sql.Context, val any, targetType *pgtypes.DoltgresType) (any, error) {
-			return timeofday.FromTime(val.(time.Time)), nil
+			return timeofday.FromTime(val.(time.Time)).ToTime(), nil
 		},
 	})
 	framework.MustAddAssignmentTypeCast(framework.TypeCast{

server/config/parameters.go

@@ -70,7 +70,7 @@ type Parameter struct {
 	Source       ParameterSource
 	ResetVal     any
 	Scope        sql.SystemVariableScope
-	ValidateFunc func(any) (any, bool)
+	ValidateFunc func(currVal, newVal any) (any, bool)
 }
 
 // GetName implements sql.SystemVariable.
@@ -90,7 +90,9 @@ func (p *Parameter) GetSessionScope() sql.SystemVariableScope {
 
 // SetDefault implements sql.SystemVariable.
 func (p *Parameter) SetDefault(a any) {
-	p.Default = a
+	if validatedVal, ok := p.ValidateFunc(p.Default, a); ok {
+		p.Default = validatedVal
+	}
 }
 
 // GetDefault implements sql.SystemVariable.
@@ -104,8 +106,12 @@ func (p *Parameter) InitValue(ctx *sql.Context, val any, global bool) (sql.Syste
 	if err != nil {
 		return sql.SystemVarValue{}, err
 	}
+	currVal, err := ctx.GetSessionVariable(ctx, p.Name)
+	if err != nil {
+		return sql.SystemVarValue{}, err
+	}
 	if p.ValidateFunc != nil {
-		v, ok := p.ValidateFunc(convertedVal)
+		v, ok := p.ValidateFunc(currVal, convertedVal)
 		if !ok {
 			return sql.SystemVarValue{}, ErrInvalidValue.New(p.Name, convertedVal)
 		}

server/config/parameters_list.go

@@ -15,6 +15,7 @@
 package config
 
 import (
+	"fmt"
 	"math"
 	"strings"
 	"time"
@@ -699,6 +700,79 @@ var postgresConfigParameters = map[string]sql.SystemVariable{
 		ResetVal:  "ISO, MDY",
 		// Sourcefile: postgresql.conf
 		Scope: GetPgsqlScope(PsqlScopeSession),
+		ValidateFunc: func(curr, new any) (any, bool) {
+			ds := "ISO"
+			do := "MDY"
+			if oldVal, ok := curr.(string); ok {
+				currentVal := strings.Split(strings.ReplaceAll(oldVal, " ", ""), ",")
+				if len(currentVal) == 2 {
+					// the first must be date style and second must be date ordering
+					ds = currentVal[0]
+					do = currentVal[1]
+				}
+			}
+			newVal, ok := new.(string)
+			if !ok {
+				return "", false
+			}
+
+			var dsSet, doSet bool
+			values := strings.Split(strings.ReplaceAll(strings.ToLower(newVal), " ", ""), ",")
+			for _, value := range values {
+				switch value {
+				case "iso":
+					if dsSet {
+						return "", false
+					}
+					ds = "ISO"
+					dsSet = true
+				case "sql":
+					if dsSet {
+						return "", false
+					}
+					ds = "SQL"
+					dsSet = true
+				case "postgres":
+					if dsSet {
+						return "", false
+					}
+					ds = "Postgres"
+					dsSet = true
+				case "german":
+					if dsSet {
+						return "", false
+					}
+					ds = "German"
+					dsSet = true
+					if !doSet {
+						do = "DMY"
+					}
+				case "us", "noneuropean", "mdy":
+					// MDY
+					if doSet {
+						return "", false
+					}
+					do = "MDY"
+					doSet = true
+				case "european", "dmy":
+					// DMY
+					if doSet {
+						return "", false
+					}
+					do = "DMY"
+					doSet = true
+				case "ymd":
+					if doSet {
+						return "", false
+					}
+					do = "YMD"
+					doSet = true
+				default:
+					return "", false
+				}
+			}
+			return fmt.Sprintf(`%s, %s`, ds, do), true
+		},
 	},
 	"db_user_namespace": &Parameter{
 		Name:      "db_user_namespace",
@@ -3464,8 +3538,8 @@ var postgresConfigParameters = map[string]sql.SystemVariable{
 		// BootVal: "GMT",
 		ResetVal: "America/Los_Angeles",
 		Scope:    GetPgsqlScope(PsqlScopeSession),
-		ValidateFunc: func(a any) (any, bool) {
-			switch v := a.(type) {
+		ValidateFunc: func(_, new any) (any, bool) {
+			switch v := new.(type) {
 			case string:
 				if strings.ToLower(v) == "local" {
 					// TODO: fix this
@@ -3486,7 +3560,7 @@ var postgresConfigParameters = map[string]sql.SystemVariable{
 					return nil, false
 				}
 			}
-			return a, true
+			return new, true
 		},
 	},
 	"timezone_abbreviations": &Parameter{

server/connection_handler.go

@@ -225,7 +225,7 @@ func (h *ConnectionHandler) handleStartup() (bool, error) {
 		if err = h.sendClientStartupMessages(); err != nil {
 			return false, err
 		}
-		if err = h.chooseInitialDatabase(sm); err != nil {
+		if err = h.chooseInitialParameters(sm); err != nil {
 			return false, err
 		}
 		return true, h.send(&pgproto3.ReadyForQuery{
@@ -282,9 +282,20 @@ func (h *ConnectionHandler) sendClientStartupMessages() error {
 	})
 }
 
-// chooseInitialDatabase attempts to choose the initial database for the connection,
-// if one is specified in the startup message provided
-func (h *ConnectionHandler) chooseInitialDatabase(startupMessage *pgproto3.StartupMessage) error {
+// chooseInitialParameters attempts to choose the initial parameter settings for the connection,
+// if one is specified in the startup message provided.
+func (h *ConnectionHandler) chooseInitialParameters(startupMessage *pgproto3.StartupMessage) error {
+	for name, value := range startupMessage.Parameters {
+		// TODO: handle other parameters defined in StartupMessage
+		switch strings.ToLower(name) {
+		case "datestyle":
+			err := h.doltgresHandler.InitSessionParameterDefault(context.Background(), h.mysqlConn, "DateStyle", value)
+			if err != nil {
+				return err
+			}
+		}
+	}
+	// set initial database
 	db, ok := startupMessage.Parameters["database"]
 	dbSpecified := ok && len(db) > 0
 	if !dbSpecified {

server/doltgres_handler.go

@@ -259,6 +259,11 @@ func (h *DoltgresHandler) NewContext(ctx context.Context, c *mysql.Conn, query s
 	return h.sm.NewContextWithQuery(ctx, c, query)
 }
 
+// InitSessionParameterDefault sets a default value to specified parameter for a session.
+func (h *DoltgresHandler) InitSessionParameterDefault(ctx context.Context, c *mysql.Conn, name, value string) error {
+	return h.sm.InitSessionDefaultVariable(ctx, c, name, value)
+}
+
 // convertBindParameters handles the conversion from bind parameters to variable values.
 func (h *DoltgresHandler) convertBindParameters(ctx *sql.Context, types []uint32, formatCodes []int16, values [][]byte) (map[string]sqlparser.Expr, error) {
 	bindings := make(map[string]sqlparser.Expr, len(values))

server/functions/date.go

@@ -15,6 +15,7 @@
 package functions
 
 import (
+	"strings"
 	"time"
 
 	"github.com/dolthub/go-mysql-server/sql"
@@ -41,15 +42,16 @@ var date_in = framework.Function1{
 	Strict:     true,
 	Callable: func(ctx *sql.Context, _ [2]*pgtypes.DoltgresType, val any) (any, error) {
 		input := val.(string)
-		if date, _, err := pgdate.ParseDate(time.Now(), pgdate.ParseModeYMD, input); err == nil {
-			return date.ToTime()
-		} else if date, _, err = pgdate.ParseDate(time.Now(), pgdate.ParseModeDMY, input); err == nil {
-			return date.ToTime()
-		} else if date, _, err = pgdate.ParseDate(time.Now(), pgdate.ParseModeMDY, input); err == nil {
-			return date.ToTime()
-		} else {
-			return nil, err
+		formatsInOrder := getDateStyleInputFormat(ctx)
+		var date pgdate.Date
+		var err error
+		for _, format := range formatsInOrder {
+			date, _, err = pgdate.ParseDate(time.Now(), format, input)
+			if err == nil {
+				return date.ToTime()
+			}
 		}
+		return nil, err
 	},
 }
 
@@ -60,7 +62,7 @@ var date_out = framework.Function1{
 	Parameters: [1]*pgtypes.DoltgresType{pgtypes.Date},
 	Strict:     true,
 	Callable: func(ctx *sql.Context, _ [2]*pgtypes.DoltgresType, val any) (any, error) {
-		return FormatDateTimeWithBC(val.(time.Time), "2006-01-02", false), nil
+		return FormatDateTimeWithBC(val.(time.Time), getLayoutStringFormat(ctx, true), false), nil
 	},
 }
 
@@ -106,3 +108,42 @@ var date_cmp = framework.Function2{
 		return int32(ab.Compare(bb)), nil
 	},
 }
+
+// getDateStyleInputFormat sets the defined format in DateStyle config as the first in the ordered list of date parsing modes.
+// TODO: this or something similar should be used in postgres/parser/sem/tree/datum.go when parsing timestamp/timestamptz/date values.
+func getDateStyleInputFormat(ctx *sql.Context) []pgdate.ParseMode {
+	formatsInOrder := []pgdate.ParseMode{pgdate.ParseModeMDY, pgdate.ParseModeDMY, pgdate.ParseModeYMD} // default
+	if ctx == nil {
+		return formatsInOrder
+	}
+	val, err := ctx.GetSessionVariable(ctx, "datestyle")
+	if err != nil {
+		return formatsInOrder
+	}
+
+	ds := strings.ReplaceAll(val.(string), " ", "")
+	values := strings.Split(ds, ",")
+	setFormat := pgdate.ParseModeYMD
+	for _, value := range values {
+		switch value {
+		case "MDY":
+			setFormat = pgdate.ParseModeMDY
+		case "DMY":
+			setFormat = pgdate.ParseModeDMY
+		case "YMD":
+			setFormat = pgdate.ParseModeYMD
+		}
+	}
+	if setFormat == formatsInOrder[0] {
+		return formatsInOrder
+	}
+
+	curFirst := formatsInOrder[0]
+	for i, f := range formatsInOrder {
+		if setFormat == f {
+			formatsInOrder[i] = curFirst
+		}
+	}
+	formatsInOrder[0] = setFormat
+	return formatsInOrder
+}