Only try to create the schema if it doesn't already exist

Signed-off-by: Irmo van den Berge <i.vdberge@valtes.nl>

server/core/db.js

@@ -190,7 +190,15 @@ module.exports = {
       // -> Create DB Schema if different than the default 'public'
       async createDefaultSchema () {
         if (WIKI.config.db.schema && WIKI.config.db.schema !== 'public') {
-          await self.knex.raw(`CREATE SCHEMA IF NOT EXISTS ${WIKI.config.db.schema};`)
+          // Don't create the schema if it already exists. This avoids errors
+          // when the user lacks permission to create new schemas while the schema
+          // already exists.
+          let matched_schemas = await self.knex.select('schema_name')
+                                               .from('information_schema.schemata')
+                                               .where('schema_name', WIKI.config.db.schema);
+          if (matched_schemas.length == 0) {
+            await self.knex.raw(`CREATE SCHEMA IF NOT EXISTS ${WIKI.config.db.schema};`)
+          }
         }
       },
       // -> Migrate DB Schemas