diff --git a/jOOQ/src/main/java/org/jooq/impl/AlterTableImpl.java b/jOOQ/src/main/java/org/jooq/impl/AlterTableImpl.java
index e64e38d74a..dca3ef3176 100644
--- a/jOOQ/src/main/java/org/jooq/impl/AlterTableImpl.java
+++ b/jOOQ/src/main/java/org/jooq/impl/AlterTableImpl.java
@@ -67,20 +67,24 @@ import static org.jooq.impl.Keywords.K_ALTER;
 import static org.jooq.impl.Keywords.K_ALTER_COLUMN;
 import static org.jooq.impl.Keywords.K_ALTER_CONSTRAINT;
 import static org.jooq.impl.Keywords.K_ALTER_TABLE;
-import static org.jooq.impl.Keywords.K_BEGIN;
 import static org.jooq.impl.Keywords.K_CASCADE;
 import static org.jooq.impl.Keywords.K_CHANGE_COLUMN;
 import static org.jooq.impl.Keywords.K_DEFAULT;
-import static org.jooq.impl.Keywords.K_DO;
 import static org.jooq.impl.Keywords.K_DROP;
 import static org.jooq.impl.Keywords.K_DROP_COLUMN;
 import static org.jooq.impl.Keywords.K_DROP_CONSTRAINT;
-import static org.jooq.impl.Keywords.K_END;
+import static org.jooq.impl.Keywords.K_ELSE;
+import static org.jooq.impl.Keywords.K_END_IF;
+import static org.jooq.impl.Keywords.K_EXCEPTION;
 import static org.jooq.impl.Keywords.K_EXEC;
+import static org.jooq.impl.Keywords.K_EXECUTE_IMMEDIATE;
+import static org.jooq.impl.Keywords.K_IF;
 import static org.jooq.impl.Keywords.K_IF_EXISTS;
+import static org.jooq.impl.Keywords.K_LIKE;
 import static org.jooq.impl.Keywords.K_MODIFY;
 import static org.jooq.impl.Keywords.K_NOT_NULL;
 import static org.jooq.impl.Keywords.K_NULL;
+import static org.jooq.impl.Keywords.K_RAISE;
 import static org.jooq.impl.Keywords.K_RENAME_COLUMN;
 import static org.jooq.impl.Keywords.K_RENAME_CONSTRAINT;
 import static org.jooq.impl.Keywords.K_RENAME_INDEX;
@@ -89,9 +93,13 @@ import static org.jooq.impl.Keywords.K_RENAME_TO;
 import static org.jooq.impl.Keywords.K_SET;
 import static org.jooq.impl.Keywords.K_SET_DATA_TYPE;
 import static org.jooq.impl.Keywords.K_SET_DEFAULT;
+import static org.jooq.impl.Keywords.K_THEN;
 import static org.jooq.impl.Keywords.K_TO;
 import static org.jooq.impl.Keywords.K_TYPE;
 import static org.jooq.impl.Keywords.K_USING_INDEX;
+import static org.jooq.impl.Keywords.K_WHEN;
+import static org.jooq.impl.Tools.begin;
+import static org.jooq.impl.Tools.end;
 import static org.jooq.impl.Tools.toSQLDDLTypeDeclaration;
 import static org.jooq.impl.Tools.toSQLDDLTypeDeclarationForAddition;
 import static org.jooq.impl.Tools.DataKey.DATA_CONSTRAINT_REFERENCE;
@@ -114,6 +122,7 @@ import org.jooq.Field;
 import org.jooq.Index;
 import org.jooq.Name;
 import org.jooq.Nullability;
+import org.jooq.Query;
 import org.jooq.SQLDialect;
 import org.jooq.Table;
 
@@ -904,18 +913,57 @@ final class AlterTableImpl extends AbstractQuery implements
     private final void alterColumnTypeAndNullabilityInBlock(Context<?> ctx) {
         boolean qualify = ctx.qualify();
 
-        ctx.visit(K_DO).sql(" $$").formatSeparator()
-           .visit(K_BEGIN).formatIndentStart().formatSeparator();
+        begin(ctx);
+
+
+
+
+
 
         accept1(ctx);
 
-        ctx.sql(';').formatSeparator()
-           .visit(K_ALTER_TABLE).sql(' ').visit(table).formatIndentStart().formatSeparator()
-           .visit(K_ALTER).sql(' ').qualify(false).visit(alterColumn).qualify(qualify).sql(' ')
-           .visit(alterColumnType.nullable() ? K_DROP : K_SET).sql(' ').visit(K_NOT_NULL).sql(';')
-           .formatIndentEnd()
-           .formatIndentEnd().formatSeparator()
-           .visit(K_END).sql(" $$");
+
+
+
+
+
+
+        ctx.sql(';').formatSeparator();
+
+        switch (ctx.family()) {
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+            case POSTGRES: {
+
+                // TODO [#6472] use jOOQ API here, once this is available
+                ctx.visit(K_ALTER_TABLE).sql(' ').visit(table).formatIndentStart().formatSeparator()
+                   .visit(K_ALTER).sql(' ').qualify(false).visit(alterColumn).qualify(qualify).sql(' ')
+                   .visit(alterColumnType.nullable() ? K_DROP : K_SET).sql(' ').visit(K_NOT_NULL).sql(';')
+                   .formatIndentEnd();
+                break;
+            }
+        }
+        end(ctx);
     }
 
     @Override
diff --git a/jOOQ/src/main/java/org/jooq/impl/Tools.java b/jOOQ/src/main/java/org/jooq/impl/Tools.java
index d5b3c5cfa2..480acdcadf 100644
--- a/jOOQ/src/main/java/org/jooq/impl/Tools.java
+++ b/jOOQ/src/main/java/org/jooq/impl/Tools.java
@@ -123,6 +123,7 @@ import static org.jooq.impl.Keywords.K_START_WITH;
 import static org.jooq.impl.Keywords.K_THEN;
 import static org.jooq.impl.Keywords.K_THROW;
 import static org.jooq.impl.Keywords.K_WHEN;
+import static org.jooq.impl.Tools.DataKey.DATA_BLOCK_NESTING;
 import static org.jooq.tools.reflect.Reflect.accessible;
 
 import java.io.Serializable;
@@ -459,6 +460,11 @@ final class Tools {
 
 
 
+
+        /**
+         * The level of anonymous block nesting, in case we're generating a block.
+         */
+        DATA_BLOCK_NESTING,
     }
 
     /**
@@ -3445,6 +3451,67 @@ final class Tools {
         return result;
     }
 
+    /**
+     * Generate the <code>BEGIN</code> part of an anonymous procedural block.
+     */
+    static final void begin(Context<?> ctx) {
+        switch (ctx.family()) {
+
+
+
+
+
+
+
+
+
+            case FIREBIRD: {
+                ctx.visit(K_EXECUTE_BLOCK).formatSeparator()
+                   .visit(K_AS).formatSeparator()
+                   .visit(K_BEGIN).formatIndentStart().formatSeparator();
+                break;
+            }
+
+            case POSTGRES: {
+                if (increment(ctx.data(), DATA_BLOCK_NESTING))
+                    ctx.visit(K_DO).sql(" $$").formatSeparator();
+
+                ctx.visit(K_BEGIN).formatIndentStart().formatSeparator();
+            }
+        }
+    }
+
+    /**
+     * Generate the <code>END</code> part of an anonymous procedural block.
+     */
+    static final void end(Context<?> ctx) {
+        switch (ctx.family()) {
+
+
+
+
+
+
+
+
+
+            case FIREBIRD: {
+                ctx.formatIndentEnd().formatSeparator()
+                   .visit(K_END);
+                break;
+            }
+            case POSTGRES: {
+                ctx.formatIndentEnd().formatSeparator()
+                   .visit(K_END);
+
+                if (decrement(ctx.data(), DATA_BLOCK_NESTING))
+                    ctx.sql(" $$");
+
+                break;
+            }
+        }
+    }
+
     /**
      * Wrap a <code>DROP .. IF EXISTS</code> statement with
      * <code>BEGIN EXECUTE IMMEDIATE '...' EXCEPTION WHEN ... END;</code>, if
@@ -3497,17 +3564,11 @@ final class Tools {
 
 
 
-
-
 
 
 
             case FIREBIRD: {
-                ctx.visit(K_EXECUTE_BLOCK).formatSeparator()
-                   .visit(K_AS).formatSeparator()
-                   .visit(K_BEGIN).formatIndentStart().formatSeparator()
-                   .visit(K_EXECUTE_STATEMENT).sql(" '").stringLiteral(true).formatIndentStart().formatSeparator();
-
+                ctx.visit(K_EXECUTE_STATEMENT).sql(" '").stringLiteral(true).formatIndentStart().formatSeparator();
                 break;
             }
 
@@ -3594,17 +3655,14 @@ final class Tools {
 
 
 
-
-
 
 
 
             case FIREBIRD: {
                 ctx.formatIndentEnd().formatSeparator().stringLiteral(false).sql("';").formatSeparator()
                    .visit(K_WHEN).sql(" sqlcode -607 ").visit(K_DO).formatIndentStart().formatSeparator()
-                   .visit(K_BEGIN).sql(' ').visit(K_END).formatIndentEnd().formatIndentEnd().formatSeparator()
-                   .visit(K_END);
-
+                   .visit(K_BEGIN).sql(' ').visit(K_END).formatIndentEnd();
+                end(ctx);
                 break;
             }
 
@@ -3715,7 +3773,6 @@ final class Tools {
 
 
 
-
             default:
                 executeImmediateEnd(ctx, type);
                 break;
@@ -3980,11 +4037,38 @@ final class Tools {
             return null;
     }
 
-    static final void increment(Map<Object, Object> data, DataKey key) {
+    /**
+     * Increment a counter and return true if the counter was zero prior to
+     * incrementing.
+     */
+    static final boolean increment(Map<Object, Object> data, DataKey key) {
+        boolean result = true;
         Integer updateCounts = (Integer) data.get(key);
+
         if (updateCounts == null)
             updateCounts = 0;
+        else
+            result = false;
+
         data.put(key, updateCounts + 1);
+        return result;
+    }
+
+    /**
+     * Decrement a counter and return true if the counter is zero after
+     * decrementing.
+     */
+    static final boolean decrement(Map<Object, Object> data, DataKey key) {
+        boolean result = false;
+        Integer updateCounts = (Integer) data.get(key);
+
+        if (updateCounts == null || updateCounts == 0)
+            throw new IllegalStateException("Unmatching increment / decrement on key: " + key);
+        else if (updateCounts == 1)
+            result = true;
+
+        data.put(key, updateCounts - 1);
+        return result;
     }
 
     static Field<?> tableField(Table<?> table, Object field) {