feat(pgsql): enhance data type mapping to support serial types

pkg/readers/pgsql/queries.go

@@ -231,14 +231,13 @@ func (r *Reader) queryColumns(schemaName string) (map[string]map[string]*models.
 		}
 
 		column := models.InitColumn(columnName, tableName, schema)
-		column.Type = r.mapDataType(dataType, udtName)
-		column.NotNull = (isNullable == "NO")
-		column.Sequence = uint(ordinalPosition)
 
+		// Check if this is a serial type (has nextval default)
+		hasNextval := false
 		if columnDefault != nil {
-			// Parse default value - remove nextval for sequences
 			defaultVal := *columnDefault
 			if strings.HasPrefix(defaultVal, "nextval") {
+				hasNextval = true
 				column.AutoIncrement = true
 				column.Default = defaultVal
 			} else {
@@ -246,6 +245,11 @@ func (r *Reader) queryColumns(schemaName string) (map[string]map[string]*models.
 			}
 		}
 
+		// Map data type, preserving serial types when detected
+		column.Type = r.mapDataType(dataType, udtName, hasNextval)
+		column.NotNull = (isNullable == "NO")
+		column.Sequence = uint(ordinalPosition)
+
 		if description != nil {
 			column.Description = *description
 		}

pkg/readers/pgsql/reader.go

@@ -3,6 +3,7 @@ package pgsql
 import (
 	"context"
 	"fmt"
+	"strings"
 
 	"github.com/jackc/pgx/v5"
 
@@ -259,33 +260,46 @@ func (r *Reader) close() {
 }
 
 // mapDataType maps PostgreSQL data types to canonical types
-func (r *Reader) mapDataType(pgType, udtName string) string {
+func (r *Reader) mapDataType(pgType, udtName string, hasNextval bool) string {
+	// If the column has a nextval default, it's likely a serial type
+	// Map to the appropriate serial type instead of the base integer type
+	if hasNextval {
+		switch strings.ToLower(pgType) {
+		case "integer", "int", "int4":
+			return "serial"
+		case "bigint", "int8":
+			return "bigserial"
+		case "smallint", "int2":
+			return "smallserial"
+		}
+	}
+
 	// Map common PostgreSQL types
 	typeMap := map[string]string{
-		"integer":                     "int",
-		"bigint":                      "int64",
-		"smallint":                    "int16",
-		"int":                         "int",
-		"int2":                        "int16",
-		"int4":                        "int",
-		"int8":                        "int64",
-		"serial":                      "int",
-		"bigserial":                   "int64",
-		"smallserial":                 "int16",
-		"numeric":                     "decimal",
+		"integer":                     "integer",
+		"bigint":                      "bigint",
+		"smallint":                    "smallint",
+		"int":                         "integer",
+		"int2":                        "smallint",
+		"int4":                        "integer",
+		"int8":                        "bigint",
+		"serial":                      "serial",
+		"bigserial":                   "bigserial",
+		"smallserial":                 "smallserial",
+		"numeric":                     "numeric",
 		"decimal":                     "decimal",
-		"real":                        "float32",
-		"double precision":            "float64",
-		"float4":                      "float32",
-		"float8":                      "float64",
-		"money":                       "decimal",
-		"character varying":           "string",
-		"varchar":                     "string",
-		"character":                   "string",
-		"char":                        "string",
-		"text":                        "string",
-		"boolean":                     "bool",
-		"bool":                        "bool",
+		"real":                        "real",
+		"double precision":            "double precision",
+		"float4":                      "real",
+		"float8":                      "double precision",
+		"money":                       "money",
+		"character varying":           "varchar",
+		"varchar":                     "varchar",
+		"character":                   "char",
+		"char":                        "char",
+		"text":                        "text",
+		"boolean":                     "boolean",
+		"bool":                        "boolean",
 		"date":                        "date",
 		"time":                        "time",
 		"time without time zone":      "time",

pkg/readers/pgsql/reader_test.go

@@ -177,20 +177,20 @@ func TestMapDataType(t *testing.T) {
 		udtName  string
 		expected string
 	}{
-		{"integer", "int4", "int"},
-		{"bigint", "int8", "int64"},
-		{"smallint", "int2", "int16"},
-		{"character varying", "varchar", "string"},
-		{"text", "text", "string"},
-		{"boolean", "bool", "bool"},
+		{"integer", "int4", "integer"},
+		{"bigint", "int8", "bigint"},
+		{"smallint", "int2", "smallint"},
+		{"character varying", "varchar", "varchar"},
+		{"text", "text", "text"},
+		{"boolean", "bool", "boolean"},
 		{"timestamp without time zone", "timestamp", "timestamp"},
 		{"timestamp with time zone", "timestamptz", "timestamptz"},
 		{"json", "json", "json"},
 		{"jsonb", "jsonb", "jsonb"},
 		{"uuid", "uuid", "uuid"},
-		{"numeric", "numeric", "decimal"},
-		{"real", "float4", "float32"},
-		{"double precision", "float8", "float64"},
+		{"numeric", "numeric", "numeric"},
+		{"real", "float4", "real"},
+		{"double precision", "float8", "double precision"},
 		{"date", "date", "date"},
 		{"time without time zone", "time", "time"},
 		{"bytea", "bytea", "bytea"},
@@ -199,12 +199,31 @@ func TestMapDataType(t *testing.T) {
 
 	for _, tt := range tests {
 		t.Run(tt.pgType, func(t *testing.T) {
-			result := reader.mapDataType(tt.pgType, tt.udtName)
+			result := reader.mapDataType(tt.pgType, tt.udtName, false)
 			if result != tt.expected {
 				t.Errorf("mapDataType(%s, %s) = %s, expected %s", tt.pgType, tt.udtName, result, tt.expected)
 			}
 		})
 	}
+
+	// Test serial type detection with hasNextval=true
+	serialTests := []struct {
+		pgType   string
+		expected string
+	}{
+		{"integer", "serial"},
+		{"bigint", "bigserial"},
+		{"smallint", "smallserial"},
+	}
+
+	for _, tt := range serialTests {
+		t.Run(tt.pgType+"_with_nextval", func(t *testing.T) {
+			result := reader.mapDataType(tt.pgType, "", true)
+			if result != tt.expected {
+				t.Errorf("mapDataType(%s, '', true) = %s, expected %s", tt.pgType, result, tt.expected)
+			}
+		})
+	}
 }
 
 func TestParseIndexDefinition(t *testing.T) {