feat(pgsql): support vector and PostGIS indexes with extensions

* Add handling for pgvector and PostGIS extensions in migration scripts
* Implement operator class and storage parameters for vector indexes
* Update tests to validate new index behaviors and extension creation

pkg/readers/pgsql/queries.go

@@ -5,6 +5,7 @@ import (
 	"strings"
 
 	"git.warky.dev/wdevs/relspecgo/pkg/models"
+	"git.warky.dev/wdevs/relspecgo/pkg/pgsql"
 )
 
 // querySchemas retrieves all non-system schemas from the database
@@ -46,6 +47,41 @@ func (r *Reader) querySchemas() ([]*models.Schema, error) {
 	return schemas, rows.Err()
 }
 
+// queryExtensions retrieves the extensions installed into a schema. Only extensions RelSpec
+// recognizes are kept, so a round-trip never emits a CREATE EXTENSION the writer cannot
+// order; plpgsql is not registered and is therefore skipped along with other built-ins.
+func (r *Reader) queryExtensions(schemaName string) ([]string, error) {
+	query := `
+		SELECT e.extname
+		FROM pg_extension e
+		JOIN pg_namespace n ON n.oid = e.extnamespace
+		WHERE n.nspname = $1
+		ORDER BY e.extname
+	`
+
+	rows, err := r.conn.Query(r.ctx, query, schemaName)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	extensions := make([]string, 0)
+	for rows.Next() {
+		var name string
+		if err := rows.Scan(&name); err != nil {
+			return nil, err
+		}
+		if pgsql.IsKnownExtension(name) {
+			extensions = append(extensions, name)
+		}
+	}
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+
+	return pgsql.SortExtensions(extensions), nil
+}
+
 // queryTables retrieves all tables for a given schema
 func (r *Reader) queryTables(schemaName string) ([]*models.Table, error) {
 	query := `
@@ -597,6 +633,7 @@ func (r *Reader) parseIndexDefinition(indexName, tableName, schema, indexDef str
 	}
 
 	// Extract columns - pattern: (column1, column2, ...)
+	opClass := ""
 	columnsRegex := regexp.MustCompile(`\(([^)]+)\)`)
 	if matches := columnsRegex.FindStringSubmatch(indexDef); len(matches) > 1 {
 		columnsStr := matches[1]
@@ -604,8 +641,17 @@ func (r *Reader) parseIndexDefinition(indexName, tableName, schema, indexDef str
 		columnParts := strings.Split(columnsStr, ",")
 		for _, col := range columnParts {
 			col = strings.TrimSpace(col)
+			fields := strings.Fields(col)
+			if len(fields) == 0 {
+				continue
+			}
+			// Remember an explicit operator class (e.g. "embedding vector_cosine_ops")
+			// so the writer can reproduce it; ordering modifiers are not operator classes.
+			if opClass == "" && len(fields) > 1 {
+				opClass = extractIndexOperatorClass(fields[1:])
+			}
 			// Remove any ordering (ASC/DESC) or other modifiers
-			col = strings.Fields(col)[0]
+			col = fields[0]
 			// Remove parentheses if it's an expression
 			if !strings.Contains(col, "(") {
 				index.Columns = append(index.Columns, col)
@@ -613,6 +659,15 @@ func (r *Reader) parseIndexDefinition(indexName, tableName, schema, indexDef str
 		}
 	}
 
+	// Extract access method storage parameters, e.g. WITH (lists='100')
+	storageParams := normalizeIndexStorageParams(pgsql.ExtractWithClause(indexDef))
+
+	// Operator class and storage parameters have no dedicated model fields; carry them in
+	// the comment hint the PostgreSQL writer reads back.
+	if hint := buildIndexHint(opClass, storageParams); hint != "" && index.Comment == "" {
+		index.Comment = hint
+	}
+
 	// Extract WHERE clause for partial indexes
 	whereRegex := regexp.MustCompile(`WHERE\s+(.+)$`)
 	if matches := whereRegex.FindStringSubmatch(indexDef); len(matches) > 1 {
@@ -622,6 +677,52 @@ func (r *Reader) parseIndexDefinition(indexName, tableName, schema, indexDef str
 	return index, nil
 }
 
+// indexOrderingKeywords are column modifiers that are not operator classes.
+var indexOrderingKeywords = map[string]bool{
+	"asc": true, "desc": true, "nulls": true, "first": true, "last": true, "collate": true,
+}
+
+// extractIndexOperatorClass picks the operator class out of a column's trailing modifiers.
+// Returns "" when the modifiers are only ordering keywords.
+func extractIndexOperatorClass(modifiers []string) string {
+	for _, modifier := range modifiers {
+		lower := strings.ToLower(strings.TrimSpace(modifier))
+		if lower == "" || indexOrderingKeywords[lower] {
+			continue
+		}
+		return lower
+	}
+	return ""
+}
+
+// normalizeIndexStorageParams rewrites "m='16', ef_construction='64'" as "m=16,
+// ef_construction=64". Non-numeric values keep their quotes because some access methods
+// require a string literal (pg_search's key_field='id').
+func normalizeIndexStorageParams(params string) string {
+	normalized := make([]string, 0, 4)
+	for _, part := range pgsql.SplitStorageParameters(params) {
+		key, value, ok := pgsql.ParseStorageParameter(part)
+		if !ok {
+			continue
+		}
+		normalized = append(normalized, key+"="+pgsql.NormalizeStorageParameterValue(value))
+	}
+	return strings.Join(normalized, ", ")
+}
+
+// buildIndexHint renders the operator class and storage parameters in the form the
+// PostgreSQL writer parses back out of an index comment.
+func buildIndexHint(opClass, storageParams string) string {
+	parts := make([]string, 0, 2)
+	if opClass != "" {
+		parts = append(parts, "opclass="+opClass)
+	}
+	if storageParams != "" {
+		parts = append(parts, "with ("+storageParams+")")
+	}
+	return strings.Join(parts, "; ")
+}
+
 // normalizePostgresDefault converts a raw PostgreSQL column_default expression into the
 // unquoted string value that the model convention expects. PostgreSQL stores string
 // literal defaults as 'value' or 'value'::type (e.g. '{}'::text[]), while every other