feat: Enhance PostgreSQL type handling and migration scripts

- Introduced equivalent base types and variants for PostgreSQL types to normalize type comparisons.
- Added functions for normalizing SQL types and retrieving equivalent type variants.
- Updated migration writer to handle type alterations with checks for existing types.
- Implemented logic to create necessary extensions (e.g., pg_trgm) based on schema requirements.
- Enhanced tests to cover new functionality for type normalization and migration handling.
- Improved handling of GIN indexes to use appropriate operator classes based on column types.

pkg/pgsql/types_registry.go

@@ -145,6 +145,24 @@ var postgresTypeAliases = map[string]string{
 	"bool": "boolean",
 }
 
+var postgresEquivalentBaseTypes = map[string]string{
+	"character varying":           "varchar",
+	"character":                   "char",
+	"timestamp without time zone": "timestamp",
+	"timestamp with time zone":    "timestamptz",
+	"time without time zone":      "time",
+	"time with time zone":         "timetz",
+}
+
+var postgresEquivalentBaseTypeVariants = map[string][]string{
+	"varchar":     {"varchar", "character varying"},
+	"char":        {"char", "character"},
+	"timestamp":   {"timestamp", "timestamp without time zone"},
+	"timestamptz": {"timestamptz", "timestamp with time zone"},
+	"time":        {"time", "time without time zone"},
+	"timetz":      {"timetz", "time with time zone"},
+}
+
 // GetPostgresBaseTypes returns a sorted-ish stable list of registered base type names.
 func GetPostgresBaseTypes() []string {
 	result := make([]string, 0, len(postgresBaseTypes))
@@ -212,6 +230,86 @@ func CanonicalizeBaseType(baseType string) string {
 	return base
 }
 
+// EquivalentBaseType resolves broader SQL-equivalent spellings to a common comparable form.
+func EquivalentBaseType(baseType string) string {
+	base := CanonicalizeBaseType(baseType)
+	if equivalent, ok := postgresEquivalentBaseTypes[base]; ok {
+		return equivalent
+	}
+	return base
+}
+
+// NormalizeEquivalentSQLType returns a normalized SQL type string suitable for equality checks.
+// Equivalent spellings such as "character varying(255)" and "varchar(255)" normalize identically.
+func NormalizeEquivalentSQLType(sqlType string) string {
+	t := normalizeTypeToken(sqlType)
+	if t == "" {
+		return ""
+	}
+
+	arrayDepth := 0
+	for strings.HasSuffix(t, "[]") {
+		arrayDepth++
+		t = strings.TrimSpace(strings.TrimSuffix(t, "[]"))
+	}
+
+	modifier := ""
+	if idx := strings.Index(t, "("); idx >= 0 {
+		modifier = strings.TrimSpace(t[idx:])
+		t = strings.TrimSpace(t[:idx])
+	}
+
+	base := EquivalentBaseType(t)
+	normalized := base + modifier
+	for i := 0; i < arrayDepth; i++ {
+		normalized += "[]"
+	}
+	return normalized
+}
+
+// EquivalentSQLTypeVariants returns equivalent PostgreSQL spellings for a SQL type.
+// Examples:
+// - varchar(255) -> ["varchar(255)", "character varying(255)"]
+// - timestamptz -> ["timestamptz", "timestamp with time zone"]
+func EquivalentSQLTypeVariants(sqlType string) []string {
+	t := normalizeTypeToken(sqlType)
+	if t == "" {
+		return nil
+	}
+
+	arrayDepth := 0
+	for strings.HasSuffix(t, "[]") {
+		arrayDepth++
+		t = strings.TrimSpace(strings.TrimSuffix(t, "[]"))
+	}
+
+	modifier := ""
+	if idx := strings.Index(t, "("); idx >= 0 {
+		modifier = strings.TrimSpace(t[idx:])
+		t = strings.TrimSpace(t[:idx])
+	}
+
+	base := EquivalentBaseType(t)
+	bases := postgresEquivalentBaseTypeVariants[base]
+	if len(bases) == 0 {
+		bases = []string{base}
+	}
+
+	seen := make(map[string]bool, len(bases))
+	result := make([]string, 0, len(bases))
+	for _, variantBase := range bases {
+		variant := variantBase + modifier
+		for i := 0; i < arrayDepth; i++ {
+			variant += "[]"
+		}
+		if !seen[variant] {
+			seen[variant] = true
+			result = append(result, variant)
+		}
+	}
+	return result
+}
+
 // IsKnownPostgresType reports whether a type (including array forms) exists in the registry.
 func IsKnownPostgresType(sqlType string) bool {
 	base := CanonicalizeBaseType(ExtractBaseTypeLower(sqlType))

pkg/pgsql/types_registry_test.go

@@ -97,3 +97,51 @@ func TestPostgresTypeRegistry_TypeParsingAndCapabilities(t *testing.T) {
 		})
 	}
 }
+
+func TestNormalizeEquivalentSQLType(t *testing.T) {
+	tests := []struct {
+		input string
+		want  string
+	}{
+		{input: "character varying(255)", want: "varchar(255)"},
+		{input: "varchar(255)", want: "varchar(255)"},
+		{input: "timestamp with time zone", want: "timestamptz"},
+		{input: "timestamptz", want: "timestamptz"},
+		{input: "time without time zone", want: "time"},
+		{input: "character varying(255)[]", want: "varchar(255)[]"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.input, func(t *testing.T) {
+			got := NormalizeEquivalentSQLType(tt.input)
+			if got != tt.want {
+				t.Fatalf("NormalizeEquivalentSQLType(%q) = %q, want %q", tt.input, got, tt.want)
+			}
+		})
+	}
+}
+
+func TestEquivalentSQLTypeVariants(t *testing.T) {
+	tests := []struct {
+		input string
+		want  []string
+	}{
+		{input: "character varying(255)", want: []string{"varchar(255)", "character varying(255)"}},
+		{input: "timestamptz", want: []string{"timestamptz", "timestamp with time zone"}},
+		{input: "text[]", want: []string{"text[]"}},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.input, func(t *testing.T) {
+			got := EquivalentSQLTypeVariants(tt.input)
+			if len(got) != len(tt.want) {
+				t.Fatalf("EquivalentSQLTypeVariants(%q) len = %d, want %d (%v)", tt.input, len(got), len(tt.want), got)
+			}
+			for i := range tt.want {
+				if got[i] != tt.want[i] {
+					t.Fatalf("EquivalentSQLTypeVariants(%q)[%d] = %q, want %q", tt.input, i, got[i], tt.want[i])
+				}
+			}
+		})
+	}
+}