Function primaryKeyColumns

backend/api/mcp/tool_schema.go:649–660

primaryKeyColumns scans indexes for the primary-key index and returns the set of column names it covers. Note: IndexMetadata.expressions may contain expressions rather than column names for expression indexes (e.g. PostgreSQL CREATE INDEX ON users (LOWER(email))). PostgreSQL does not currently allo

(indexes []indexMetadata)

// expression text against column name is correct today. Revisit if PG ever
// allows expression PKs; silent misses are preferred over flagging the wrong column.
func primaryKeyColumns(indexes []indexMetadata) map[string]bool {
	result := map[string]bool{}
	for _, idx := range indexes {
		if !idx.Primary {
			continue
		}
		for _, expr := range idx.Expressions {
			result[expr] = true
		}
	}
	return result
}

// formatSchemaOutput produces a text header + JSON body (same pattern as query_database).
func formatSchemaOutput(output *SchemaOutput, include string, warnings []string) string {