On 11/18/20 8:05 AM, Stephen Haddock wrote: > Hello, > > When upgrading an older version of postgres, version 8.4 for example, to > a newer version such as 9.6, does the data have to be migrated immediately? > > It looks like the recommended method is to dump the data, upgrade, > initialize a new cluster, and then restore the dumped data into the > newer version. My question is whether the data dump and restore must be > done immediately. It appears that 9.6 is able to run against the older > cluster (DB service starts, queries work, etc), and the data could be
Hmm, missed that. As David said that should not happen and if you are running a new binary against an old cluster then you will get corruption.
Actually, upon re-reading I suspect you are more likely correct. Depending on the package/installer both 8.4 and 9.6 are both able to run on the server simultaneously - on different ports. Upgrading PostgreSQL to 9.6 only installs the database programs and, usually, a default cluster (using the next available port number) having a "postgres" database (it's not really an upgrade if the major version changes, it's a new install). Separately, the DBA must initiate an upgrade of clusters (or dump/reload of individual databases) that they wish to run under the newly installed 9.6 version.