diff --git a/api/src/org/labkey/api/data/DbScope.java b/api/src/org/labkey/api/data/DbScope.java
index 4a7b1e1ed75..d20efe56caa 100644
--- a/api/src/org/labkey/api/data/DbScope.java
+++ b/api/src/org/labkey/api/data/DbScope.java
@@ -368,6 +368,21 @@ public LabKeyDataSource(DataSource ds, String dsName) throws ServletException
             _dialect = SqlDialectManager.getFromDriverClassname(_dsName, _driverClassName);
             MemTracker.get().remove(_dialect);
             _driverClass = initializeDriver();
+
+            if (_dialect.isPostgreSQL())
+            {
+                // Starting with PostgreSQL 17.x, we can't connect with a database name longer than 63 chars, so we have
+                // to truncate and replace the URL in the DataSource. Yuck. Issue #51676.
+                String url = _dsPropertyReader.getUrl();
+                String name = _dialect.getDatabaseName(url);
+                if (name.length() > _dialect.getIdentifierMaxLength())
+                {
+                    String truncated = StringUtils.truncate(name, _dialect.getIdentifierMaxLength());
+                    String newUrl = url.replace(name, truncated);
+                    _dsPropertyReader.setUrl(newUrl);
+                }
+            }
+
             _url = _dsPropertyReader.getUrl();
 
             // Validate that data source is using a supported connection pool
diff --git a/api/src/org/labkey/api/data/LookupColumn.java b/api/src/org/labkey/api/data/LookupColumn.java
index d2f110252f0..d4bf39aa5ca 100644
--- a/api/src/org/labkey/api/data/LookupColumn.java
+++ b/api/src/org/labkey/api/data/LookupColumn.java
@@ -24,10 +24,8 @@
 import org.labkey.api.util.Pair;
 
 import java.util.Collections;
-import java.util.HashSet;
 import java.util.LinkedHashMap;
 import java.util.Map;
-import java.util.Set;
 
 /**
  * A {@link org.labkey.api.data.ColumnInfo} that is part of a lookup target. This implementation knows
@@ -133,7 +131,7 @@ public LookupColumn(ColumnInfo foreignKey, ColumnInfo lookupKey, ColumnInfo look
         _joinType = joinType;
         setSqlTypeName(lookupColumn.getSqlTypeName());
         String alias = foreignKey.getAlias() + "$" + lookupColumn.getAlias();
-        int maxLength = lookupColumn.getSqlDialect().getIdentifierMaxLength();
+        int maxLength = lookupColumn.getSqlDialect().getIdentifierMaxLength() - 3; // Leave room for "$" and possible suffixes
         if (alias.length() > maxLength)
             alias = AliasManager.truncate(foreignKey.getAlias(),maxLength/2) + "$" + AliasManager.truncate(lookupColumn.getAlias(),maxLength/2);
         setAlias(alias);
@@ -282,7 +280,7 @@ public static String getTableAlias(String baseAlias, String fkAlias, SqlDialect
     {
         String alias = baseAlias + (baseAlias.endsWith("$")?"":"$") + fkAlias + "$";
 
-        alias = AliasManager.truncate(alias, dialect.getIdentifierMaxLength());
+        alias = AliasManager.truncate(alias, dialect.getIdentifierMaxLength() - 3 /* leave room for possible suffixes */);
         return alias;
     }
 
diff --git a/api/src/org/labkey/api/data/dialect/PostgreSql91Dialect.java b/api/src/org/labkey/api/data/dialect/PostgreSql91Dialect.java
index f52eb5df07b..d5acb08de20 100644
--- a/api/src/org/labkey/api/data/dialect/PostgreSql91Dialect.java
+++ b/api/src/org/labkey/api/data/dialect/PostgreSql91Dialect.java
@@ -637,8 +637,7 @@ public String getCreateDatabaseSql(String dbName)
     {
         // This will handle both mixed case and special characters on PostgreSQL
         String legal = getSelectNameFromMetaDataName(dbName);
-        return "CREATE DATABASE " + legal + " WITH ENCODING 'UTF8';\n" +
-                "ALTER DATABASE " + legal + " SET default_with_oids TO OFF";
+        return "CREATE DATABASE " + legal + " WITH ENCODING 'UTF8'";
     }
 
     @Override
diff --git a/api/src/org/labkey/api/data/dialect/SqlDialect.java b/api/src/org/labkey/api/data/dialect/SqlDialect.java
index 77c3a06a594..bf5924f00f5 100644
--- a/api/src/org/labkey/api/data/dialect/SqlDialect.java
+++ b/api/src/org/labkey/api/data/dialect/SqlDialect.java
@@ -958,11 +958,13 @@ public void testKeywordCandidates(SqlExecutor executor) throws IOException, SQLE
             throw new IllegalStateException(getProductName() + " reserved words are not all in the keyword candidate list (sqlKeywords.txt). See log for details.");
     }
 
+    /**
+     * @return The absolute maximum length for this database. Callers are responsible for truncating generated names,
+     * handing suffixes, etc.
+     */
     public int getIdentifierMaxLength()
     {
-        // 63 probably works, but save 2 chars for appending chars to
-        // create aliases for extra tables used in the lookup (e.g. junctionAlias = getTableAlias() + "_j")
-        return 61;
+        return 63;
     }
 
     protected SQLFragment getIdentifierTestSql(String candidate)
@@ -1344,6 +1346,20 @@ public Long getMaxWaitMillis()
                 return null;
             }
         }
+
+        public void setUrl(String url) throws ServletException
+        {
+            String methodName = "setUrl";
+            try
+            {
+                Method method = _ds.getClass().getMethod(methodName, String.class);
+                method.invoke(_ds, url);
+            }
+            catch (Exception e)
+            {
+                throw new ServletException("Unable to set DataSource property via " + methodName, e);
+            }
+        }
     }
 
     // All statement creation passes through these two methods. We return our standard statement wrappers in most
diff --git a/api/src/org/labkey/api/query/AliasManager.java b/api/src/org/labkey/api/query/AliasManager.java
index bb818b599c3..4c312b032bc 100644
--- a/api/src/org/labkey/api/query/AliasManager.java
+++ b/api/src/org/labkey/api/query/AliasManager.java
@@ -178,8 +178,7 @@ private static String makeLegalName(String str, @Nullable SqlDialect dialect, bo
             ret = "X_";
         if (dialect != null)
             ret = dialect.makeLegalIdentifierName(ret);
-        // we use 28 here because Oracle has a limit or 30 characters, and that is likely the shortest restriction
-        int maxLength = useLegacyMaxLength ? 40 : (dialect == null ? 28 : dialect.getIdentifierMaxLength());
+        int maxLength = getMaxLength(dialect, useLegacyMaxLength);
         if (reserveCount > 0)
             maxLength -= reserveCount;
         if (maxLength < 5)
@@ -202,12 +201,18 @@ public static String makeLegalName(FieldKey key, @Nullable SqlDialect dialect, b
             sb.append(legalNameFromName(part));
             connector = "_";
         }
-        // we use 28 here because Oracle has a limit or 30 characters, and that is likely the shortest restriction
-        var ret = truncate(sb.toString(), useLegacyMaxLength ? 40 : (dialect == null ? 28 : dialect.getIdentifierMaxLength()));
+        var ret = truncate(sb.toString(), getMaxLength(dialect, useLegacyMaxLength));
         assert isLegalName(ret);
         return ret;
     }
 
+    private static int getMaxLength(@Nullable SqlDialect dialect, boolean useLegacyMaxLength)
+    {
+        // we use 28 here because Oracle has a limit of 30 characters, and that is likely the shortest restriction
+
+        // But note: Oracle 12c raised the limit to 128 characters, so perhaps increase the fall-back length now?
+        return useLegacyMaxLength ? 40 : (dialect == null ? 28 : dialect.getIdentifierMaxLength() - 3 /* leave room for possible suffixes */);
+    }
 
     public static String truncate(String str, int to)
     {
@@ -375,7 +380,7 @@ public boolean isReserved(String word)
 
             assertEquals("select_", m.decideAlias("select"));
 
-            assertEquals(m._dialect.getIdentifierMaxLength(), m.decideAlias("This is a very long name for a column, but it happens! go figure.").length());
+            assertEquals(m._dialect.getIdentifierMaxLength() - 3, m.decideAlias("This is a very long name for a column, but it happens! go figure. " + StringUtils.repeat('x', 100)).length());
         }
     }
 }