It might look like a map of the London Underground designed by a madman, but Gartner's newly-completed DBMS Market Share Ranks: 2011-2025 has an important message. The change may be glacial, but (most of the) dominant database vendors are slowly losing their grip on the market. Author Adam Ronthal, vice president analyst at Gartner, pointed out: "Of the leading vendors in 2011 (Oracle, IBM, Microsoft, and SAP), only Microsoft has grown their market share in the last 15 years. The others have ceded market share to Amazon, Google Cloud Platform, and a handful of smaller but emerging vendors like Snowflake, Databricks, and MongoDB. There is no reason to expect this trend to reverse itself in the foreseeable future." Gartner's DBMS Market Share Ranks is a stack ranking of revenue. PostgreSQL, MySQL, Cassandra, and other popular open source systems are not measured in and of themselves – only as part of commercial services. The market is stable at the top.…