Merge lp:~nwilliams/akiban-server/alter-generated into lp:~akiban-technologies/akiban-server/trunk

[Nathan Williams]

Support SET INCREMENT and GENERATED ALTER actions.

A little tweaking in handling DEFAULT nodes in AlterTableDDL and a little propagation of new sequences through the validator and merger.

Minor tweaks and helper methods elsewhere.

[Mike McMahon (mmcm)]

Looks right and passes new tests. Is line 87 leftover from an earlier stage of tracking the change? newSequences doesn't seem to get used.

review: Needs Information

[lp:~nwilliams/akiban-server/alter-generated]

2626. By Nathan Williams on 2013-04-15

Remove dead variable

[Nathan Williams (nwilliams)]

Indeed it was. Removed.

[Mike McMahon (mmcm)]

Uncovered trying to update the client-tools test for this: DumpClient assumes that identity sequences are named _sequence-XXX, whereas one added by ALTER is still called temp-sequence-1. I assume that name will cause other kinds of trouble, but it is possible to alter the dumper, of course.

review: Needs Information

[Nathan Williams (nwilliams)]

Wasn't using as much of the helper as I thought I was. Fixed.

Good catch. Why does DumpClient assume that? Is there no other indication that it is an identity column?

[lp:~nwilliams/akiban-server/alter-generated]

2627. By Nathan Williams on 2013-04-15

Use helper for sequence name.

2628. By Nathan Williams on 2013-04-15

Cleanup

[Mike McMahon (mmcm)]

Looks good.

review: Approve

=== modified file 'src/main/java/com/akiban/ais/model/AISBuilder.java'
--- src/main/java/com/akiban/ais/model/AISBuilder.java	2013-03-22 20:05:57 +0000
+++ src/main/java/com/akiban/ais/model/AISBuilder.java	2013-04-15 20:33:27 +0000
@@ -75,12 +75,12 @@
         return nameGenerator;
     }
 
-    public void sequence (String schemaName, String sequenceName,
-            long start, long increment,
-            long minValue, long maxValue, boolean cycle) {
+    public Sequence sequence(String schemaName, String sequenceName,
+                             long start, long increment, long minValue, long maxValue, boolean cycle) {
         LOG.trace("sequence: {}.{} ", schemaName,sequenceName);
         Sequence identityGenerator = Sequence.create(ais, schemaName, sequenceName, start, increment, minValue, maxValue, cycle);
         identityGenerator.setTreeName(nameGenerator.generateSequenceTreeName(identityGenerator));
+        return identityGenerator;
     }
     
     public UserTable userTable(String schemaName, String tableName) {

=== modified file 'src/main/java/com/akiban/ais/model/AISMerge.java'
--- src/main/java/com/akiban/ais/model/AISMerge.java	2013-04-11 03:40:21 +0000
+++ src/main/java/com/akiban/ais/model/AISMerge.java	2013-04-15 20:33:27 +0000
@@ -86,6 +86,20 @@
         }
     }
 
+    private static class IdentityInfo {
+        public final TableName tableName;
+        public final String columnName;
+        public final boolean defaultIdentity;
+        public final Sequence sequence;
+
+        public IdentityInfo(TableName tableName, String columnName, boolean defaultIdentity, Sequence sequence) {
+            this.tableName = tableName;
+            this.columnName = columnName;
+            this.defaultIdentity = defaultIdentity;
+            this.sequence = sequence;
+        }
+    }
+
     private static final Logger LOG = LoggerFactory.getLogger(AISMerge.class);
 
     /* state */
@@ -95,16 +109,17 @@
     private final MergeType mergeType;
     private final List<JoinChange> changedJoins;
     private final Map<IndexName,IndexInfo> indexesToFix;
+    private final List<IdentityInfo> identityToFix;
 
 
     /** Legacy test constructor. Creates an AISMerge for adding a table with a new {@link DefaultNameGenerator}. */
     AISMerge(AkibanInformationSchema sourceAIS, UserTable newTable) {
-        this(new DefaultNameGenerator(sourceAIS), copyAISForAdd(sourceAIS), newTable, MergeType.ADD_TABLE, null, null);
+        this(new DefaultNameGenerator(sourceAIS), copyAISForAdd(sourceAIS), newTable, MergeType.ADD_TABLE, null, null, null);
     }
 
     /** Create a new AISMerge to be used for adding a new table. */
     public static AISMerge newForAddTable(NameGenerator generator, AkibanInformationSchema sourceAIS, UserTable newTable) {
-        return new AISMerge(generator, copyAISForAdd(sourceAIS), newTable, MergeType.ADD_TABLE, null, null);
+        return new AISMerge(generator, copyAISForAdd(sourceAIS), newTable, MergeType.ADD_TABLE, null, null, null);
     }
 
     /** Create a new AISMerge to be used for modifying a table. */
@@ -112,27 +127,30 @@
                                              Collection<ChangedTableDescription> alteredTables) {
         List<JoinChange> changedJoins = new ArrayList<>();
         Map<IndexName,IndexInfo> indexesToFix = new HashMap<>();
-        AkibanInformationSchema targetAIS = copyAISForModify(sourceAIS, indexesToFix, changedJoins, alteredTables);
-        return new AISMerge(generator, targetAIS, null, MergeType.MODIFY_TABLE, changedJoins, indexesToFix);
+        List<IdentityInfo> identityToFix = new ArrayList<>();
+        AkibanInformationSchema targetAIS = copyAISForModify(sourceAIS, indexesToFix, changedJoins, identityToFix, alteredTables);
+        return new AISMerge(generator, targetAIS, null, MergeType.MODIFY_TABLE, changedJoins, indexesToFix, identityToFix);
     }
 
     /** Create a new AISMerge to be used for adding one, or more, index to a table. Also see {@link #mergeIndex(Index)}. */
     public static AISMerge newForAddIndex(NameGenerator generator, AkibanInformationSchema sourceAIS) {
-        return new AISMerge(generator, copyAISForAdd(sourceAIS), null, MergeType.ADD_INDEX, null, null);
+        return new AISMerge(generator, copyAISForAdd(sourceAIS), null, MergeType.ADD_INDEX, null, null, null);
     }
 
     public static AISMerge newForOther(NameGenerator generator, AkibanInformationSchema sourceAIS) {
-        return new AISMerge(generator, copyAISForAdd(sourceAIS), null, MergeType.OTHER, null, null);
+        return new AISMerge(generator, copyAISForAdd(sourceAIS), null, MergeType.OTHER, null, null, null);
     }
 
     private AISMerge(NameGenerator nameGenerator, AkibanInformationSchema targetAIS, UserTable sourceTable,
-                     MergeType mergeType, List<JoinChange> changedJoins, Map<IndexName,IndexInfo> indexesToFix) {
+                     MergeType mergeType, List<JoinChange> changedJoins, Map<IndexName,IndexInfo> indexesToFix,
+                     List<IdentityInfo> identityToFix) {
         this.nameGenerator = nameGenerator;
         this.targetAIS = targetAIS;
         this.sourceTable = sourceTable;
         this.mergeType = mergeType;
         this.changedJoins = changedJoins;
         this.indexesToFix = indexesToFix;
+        this.identityToFix = identityToFix;
     }
 
 
@@ -143,6 +161,7 @@
     private static AkibanInformationSchema copyAISForModify(AkibanInformationSchema oldAIS,
                                                             Map<IndexName,IndexInfo> indexesToFix,
                                                             final List<JoinChange> joinsToFix,
+                                                            List<IdentityInfo> identityToFix,
                                                             Collection<ChangedTableDescription> changedTables)
     {
         final Set<Sequence> excludedSequences = new HashSet<>();
@@ -218,6 +237,11 @@
             for(TableName name : desc.getDroppedSequences()) {
                 excludedSequences.add(oldAIS.getSequence(name));
             }
+
+            for(String name : desc.getIdentityAdded()) {
+                Column col = newTable.getColumn(name);
+                identityToFix.add(new IdentityInfo(desc.getNewName(), name, col.getDefaultIdentity(), col.getIdentityGenerator()));
+            }
         }
 
         return AISCloner.clone(
@@ -481,6 +505,11 @@
             index.setTreeName((info.tree != null) ? info.tree : nameGenerator.generateIndexTreeName(index));
         }
 
+        for(IdentityInfo info : identityToFix) {
+            addIdentitySequence(builder, info.tableName.getSchemaName(), info.tableName.getTableName(), info.columnName,
+                                info.defaultIdentity, info.sequence);
+        }
+
         builder.akibanInformationSchema().validate(AISValidations.LIVE_AIS_VALIDATIONS).throwIfNecessary();
         builder.akibanInformationSchema().freeze();
     }
@@ -529,16 +558,8 @@
                 newColumn.setInitialAutoIncrementValue(column.getInitialAutoIncrementValue());
             }
             if (column.getDefaultIdentity() != null) {
-                TableName sequenceName = nameGenerator.generateIdentitySequenceName(new TableName(schemaName, tableName));
-                Sequence sequence = column.getIdentityGenerator();
-                builder.sequence(sequenceName.getSchemaName(), sequenceName.getTableName(),
-                        sequence.getStartsWith(), 
-                        sequence.getIncrement(), 
-                        sequence.getMinValue(), 
-                        sequence.getMaxValue(), 
-                        sequence.isCycle());
-                builder.columnAsIdentity(schemaName, tableName, column.getName(), sequenceName.getTableName(), column.getDefaultIdentity());
-                LOG.debug("Generated sequence: {}, with tree name; {}", sequenceName, sequence.getTreeName());
+                addIdentitySequence(builder, schemaName, tableName, column.getName(),
+                                    column.getDefaultIdentity(), column.getIdentityGenerator());
             }
             // Proactively cache, can go away if Column ever cleans itself up
             newColumn.getMaxStorageSize();
@@ -546,6 +567,19 @@
         }
     }
 
+    private void addIdentitySequence(AISBuilder builder, String schemaName, String tableName, String column,
+                                     boolean defaultIdentity, Sequence sequence) {
+        TableName sequenceName = nameGenerator.generateIdentitySequenceName(new TableName(schemaName, tableName));
+        Sequence newSeq = builder.sequence(sequenceName.getSchemaName(), sequenceName.getTableName(),
+                                           sequence.getStartsWith(),
+                                           sequence.getIncrement(),
+                                           sequence.getMinValue(),
+                                           sequence.getMaxValue(),
+                                           sequence.isCycle());
+        builder.columnAsIdentity(schemaName, tableName, column, sequenceName.getTableName(), defaultIdentity);
+        LOG.debug("Generated sequence: {}, with tree name; {}", sequenceName, newSeq.getTreeName());
+    }
+
     private void addNewGroup (AISBuilder builder, UserTable rootTable) {
         TableName groupName = rootTable.getName();
         builder.createGroup(groupName.getTableName(), groupName.getSchemaName());
@@ -650,13 +684,18 @@
     
     public AkibanInformationSchema mergeSequence(Sequence sequence)
     {
+        mergeSequenceInternal(sequence);
+        targetAIS.validate(AISValidations.LIVE_AIS_VALIDATIONS).throwIfNecessary();
+        targetAIS.freeze();
+        return targetAIS;
+    }
+
+    private Sequence mergeSequenceInternal(Sequence sequence)
+    {
         Sequence newSeq = Sequence.create(targetAIS, sequence);
         newSeq.setTreeName(nameGenerator.generateSequenceTreeName(newSeq));
-        targetAIS.addSequence(newSeq);
-        targetAIS.validate(AISValidations.LIVE_AIS_VALIDATIONS).throwIfNecessary();
-        targetAIS.freeze();
-        return targetAIS;
-    }    
+        return newSeq;
+    }
 
     public static AkibanInformationSchema mergeRoutine(AkibanInformationSchema oldAIS,
                                                        Routine routine) {

=== modified file 'src/main/java/com/akiban/ais/model/AkibanInformationSchema.java'
--- src/main/java/com/akiban/ais/model/AkibanInformationSchema.java	2013-03-22 20:05:57 +0000
+++ src/main/java/com/akiban/ais/model/AkibanInformationSchema.java	2013-04-15 20:33:27 +0000
@@ -642,7 +642,7 @@
         invalidateTableIdMap();
     }
     
-    void removeSequence (TableName name) {
+    public void removeSequence (TableName name) {
         sequences.remove(name);
         Schema schema = getSchema(name.getSchemaName());
         if (schema != null) {

=== modified file 'src/main/java/com/akiban/ais/model/DefaultNameGenerator.java'
--- src/main/java/com/akiban/ais/model/DefaultNameGenerator.java	2013-03-22 20:05:57 +0000
+++ src/main/java/com/akiban/ais/model/DefaultNameGenerator.java	2013-04-15 20:33:27 +0000
@@ -34,6 +34,8 @@
 public class DefaultNameGenerator implements NameGenerator {
     private static final Logger LOG = LoggerFactory.getLogger(DefaultNameGenerator.class);
 
+    public static final String IDENTITY_SEQUENCE_PREFIX = "_sequence-";
+
     // Use 1 as default offset because the AAM uses tableID 0 as a marker value.
     static final int USER_TABLE_ID_OFFSET = 1;
     static final int IS_TABLE_ID_OFFSET = 1000000000;
@@ -99,7 +101,7 @@
 
     @Override
     public TableName generateIdentitySequenceName(TableName tableName) {
-        TableName seqName = new TableName(tableName.getSchemaName(), "_sequence-" + tableName.hashCode());
+        TableName seqName = new TableName(tableName.getSchemaName(), IDENTITY_SEQUENCE_PREFIX + tableName.hashCode());
         return makeUnique(sequenceNames, seqName);
     }
 

=== modified file 'src/main/java/com/akiban/ais/model/aisb2/AISBBasedBuilder.java'
--- src/main/java/com/akiban/ais/model/aisb2/AISBBasedBuilder.java	2013-04-10 23:46:56 +0000
+++ src/main/java/com/akiban/ais/model/aisb2/AISBBasedBuilder.java	2013-04-15 20:33:27 +0000
@@ -214,29 +214,35 @@
 
         @Override
         public NewUserTableBuilder colLong(String name) {
-            return colLong(name, NULLABLE_DEFAULT, null);
+            return colLong(name, NULLABLE_DEFAULT, null, null);
         }
 
         @Override
         public NewUserTableBuilder colLong(String name, boolean nullable) {
-            return colLong(name, nullable, null);
+            return colLong(name, nullable, null, null);
         }
 
         @Override
         public NewUserTableBuilder autoIncLong(String name, int initialValue) {
-            return colLong(name, false, initialValue);
-        }
-
-        private NewUserTableBuilder colLong(String name, boolean nullable, Integer initialAutoInc) {
+            return colLong(name, false, initialValue, true);
+        }
+
+        @Override
+        public NewUserTableBuilder autoIncLong(String name, int initialValue, boolean always) {
+            return colLong(name, false, initialValue, !always);
+        }
+
+        private NewUserTableBuilder colLong(String name, boolean nullable, Integer initialAutoInc, Boolean defaultIdentity) {
             checkUsable();
             aisb.column(schema, userTable, name, uTableColumnPos++, "INT", 10L, null, nullable, false, null, null);
             if (initialAutoInc != null) {
+                assert defaultIdentity != null;
                 String sequenceName = "temp-seq-" + userTable + "-" + name;
                 long initValue = initialAutoInc.longValue();
                 aisb.sequence(schema, sequenceName, 
                               initValue, 1L, initValue, Long.MAX_VALUE,
                               false);
-                aisb.columnAsIdentity(schema, userTable, name, sequenceName, true);
+                aisb.columnAsIdentity(schema, userTable, name, sequenceName, defaultIdentity);
                 aisb.akibanInformationSchema().
                      getUserTable(schema, userTable).
                      getColumn(name).

=== modified file 'src/main/java/com/akiban/ais/model/aisb2/NewUserTableBuilder.java'
--- src/main/java/com/akiban/ais/model/aisb2/NewUserTableBuilder.java	2013-04-01 18:36:36 +0000
+++ src/main/java/com/akiban/ais/model/aisb2/NewUserTableBuilder.java	2013-04-15 20:33:27 +0000
@@ -67,13 +67,23 @@
     NewUserTableBuilder colLong(String name, boolean nullable);
 
     /**
-     * Adds a non-nullable, sequence backed, auto-incrementing column
+     * Adds a non-nullable, sequence backed, auto-incrementing BY DEFAULT identity column
      * @param name the column's name
+     * @param initialValue the START WITH value
      * @return this
      */
     NewUserTableBuilder autoIncLong(String name, int initialValue);
 
     /**
+     * Adds a non-nullable, sequence backed, auto-incrementing identity column
+     * @param name the column's name
+     * @param initialValue the START WITH value
+     * @param always ALWAYS if <code>true</code>, otherwise DEFAULT
+     * @return this
+     */
+    NewUserTableBuilder autoIncLong(String name, int initialValue, boolean always);
+
+    /**
      * Adds an optionally nullable boolean column
      * @param name the column's name
      * @param nullable whether the column is nullable

=== modified file 'src/main/java/com/akiban/ais/util/ChangedTableDescription.java'
--- src/main/java/com/akiban/ais/util/ChangedTableDescription.java	2013-03-22 20:05:57 +0000
+++ src/main/java/com/akiban/ais/util/ChangedTableDescription.java	2013-04-15 20:33:27 +0000
@@ -38,6 +38,7 @@
     private final Map<String,String> parentColNames;
     private final Map<String,String> preserveIndexes;
     private final Collection<TableName> droppedSequences;
+    private final Collection<String> identityAdded;
 
     /**
      * @param tableName Current name of the table being changed.
@@ -46,7 +47,8 @@
      */
     public ChangedTableDescription(TableName tableName, UserTable newDefinition, Map<String,String> colNames,
                                    ParentChange parentChange, TableName parentName, Map<String,String> parentColNames,
-                                   Map<String, String> preserveIndexes, Collection<TableName> droppedSequences) {
+                                   Map<String, String> preserveIndexes, Collection<TableName> droppedSequences,
+                                   Collection<String> identityAdded) {
         ArgumentValidation.notNull("tableName", tableName);
         ArgumentValidation.notNull("preserveIndexes", preserveIndexes);
         this.tableName = tableName;
@@ -57,6 +59,7 @@
         this.parentColNames = parentColNames;
         this.preserveIndexes = preserveIndexes;
         this.droppedSequences = droppedSequences;
+        this.identityAdded = identityAdded;
     }
 
     public TableName getOldName() {
@@ -95,6 +98,10 @@
         return droppedSequences;
     }
 
+    public Collection<String> getIdentityAdded() {
+        return identityAdded;
+    }
+
     public boolean isNewGroup() {
         return (parentChange != ParentChange.NONE);
     }

=== modified file 'src/main/java/com/akiban/ais/util/TableChangeValidator.java'
--- src/main/java/com/akiban/ais/util/TableChangeValidator.java	2013-04-11 04:48:29 +0000
+++ src/main/java/com/akiban/ais/util/TableChangeValidator.java	2013-04-15 20:33:27 +0000
@@ -393,9 +393,9 @@
         primaryKeyChanged = containsOldOrNew(indexChanges, Index.PRIMARY_KEY_CONSTRAINT);
 
         List<TableName> droppedSequences = new ArrayList<>();
+        List<String> addedIdentity = new ArrayList<>();
         Map<String,String> renamedColumns = new HashMap<>();
         for(TableChange change : columnChanges) {
-            Sequence seqToDrop = null;
             switch(change.getChangeType()) {
                 case MODIFY: {
                     if(!change.getOldName().equals(change.getNewName())) {
@@ -403,20 +403,24 @@
                     }
                     Column oldColumn = oldTable.getColumn(change.getOldName());
                     Column newColumn = newTable.getColumn(change.getNewName());
-                    if((oldColumn != null) && (oldColumn.getIdentityGenerator() != null) && (newColumn.getIdentityGenerator() == null)) {
-                        seqToDrop = oldColumn.getIdentityGenerator();
+                    if((oldColumn != null)) {
+                        Sequence oldSeq = oldColumn.getIdentityGenerator();
+                        Sequence newSeq = newColumn.getIdentityGenerator();
+                        if((oldSeq == null) && (newSeq != null)) {
+                            addedIdentity.add(newColumn.getName());
+                        } else if((oldSeq != null) && (newSeq == null)) {
+                            droppedSequences.add(oldSeq.getSequenceName());
+                        }
+                        // else both not null and not equal, not yet supported
                     }
                 } break;
                 case DROP: {
                     Column oldColumn = oldTable.getColumn(change.getOldName());
-                    if(oldColumn != null) {
-                        seqToDrop = oldColumn.getIdentityGenerator();
+                    if((oldColumn != null) && (oldColumn.getIdentityGenerator() != null)) {
+                        droppedSequences.add(oldColumn.getIdentityGenerator().getSequenceName());
                     }
                 } break;
             }
-            if(seqToDrop != null) {
-                droppedSequences.add(seqToDrop.getSequenceName());
-            }
         }
 
         boolean renamed = !oldTable.getName().equals(newTable.getName()) || !renamedColumns.isEmpty();
@@ -425,7 +429,7 @@
         TableName parentName = (newTable.getParentJoin() != null) ? newTable.getParentJoin().getParent().getName() : null;
         changedTables.add(new ChangedTableDescription(oldTable.getName(), newTable, renamedColumns,
                                                       parentChange, parentName, EMPTY_STRING_MAP, preserveIndexes,
-                                                      droppedSequences));
+                                                      droppedSequences, addedIdentity));
 
         if(!isParentChanged() && !primaryKeyChanged) {
             for(Index index : newTable.getIndexesIncludingInternal()) {
@@ -507,7 +511,7 @@
         parentRenames = (parentRenames != null) ? parentRenames : EMPTY_STRING_MAP;
         changedTables.add(new ChangedTableDescription(table.getName(), null, EMPTY_STRING_MAP,
                                                       parentChange, parentName, parentRenames, preserved,
-                                                      EMPTY_TABLE_NAME_LIST));
+                                                      EMPTY_TABLE_NAME_LIST, Collections.<String>emptyList()));
     }
 
     private static boolean containsOldOrNew(List<TableChange> changes, String name) {

=== added file 'src/main/java/com/akiban/server/error/ColumnAlreadyGeneratedException.java'
--- src/main/java/com/akiban/server/error/ColumnAlreadyGeneratedException.java	1970-01-01 00:00:00 +0000
+++ src/main/java/com/akiban/server/error/ColumnAlreadyGeneratedException.java	2013-04-15 20:33:27 +0000
@@ -0,0 +1,31 @@
+/**
+ * Copyright (C) 2009-2013 Akiban Technologies, Inc.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package com.akiban.server.error;
+
+import com.akiban.ais.model.Column;
+
+public class ColumnAlreadyGeneratedException extends InvalidOperationException {
+    public ColumnAlreadyGeneratedException(Column column) {
+        super(ErrorCode.COLUMN_ALREADY_GENERATED,
+              column.getColumnar().getName().getSchemaName(),
+              column.getColumnar().getName().getTableName(),
+              column.getName(),
+              column.getIdentityGenerator().getSchemaName(),
+              column.getIdentityGenerator().getSequenceName().getTableName());
+    }
+}

=== added file 'src/main/java/com/akiban/server/error/ColumnNotGeneratedException.java'
--- src/main/java/com/akiban/server/error/ColumnNotGeneratedException.java	1970-01-01 00:00:00 +0000
+++ src/main/java/com/akiban/server/error/ColumnNotGeneratedException.java	2013-04-15 20:33:27 +0000
@@ -0,0 +1,29 @@
+/**
+ * Copyright (C) 2009-2013 Akiban Technologies, Inc.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package com.akiban.server.error;
+
+import com.akiban.ais.model.Column;
+
+public class ColumnNotGeneratedException extends InvalidOperationException {
+    public ColumnNotGeneratedException(Column column) {
+        super(ErrorCode.COLUMN_NOT_GENERATED,
+              column.getColumnar().getName().getSchemaName(),
+              column.getColumnar().getName().getTableName(),
+              column.getName());
+    }
+}

=== modified file 'src/main/java/com/akiban/server/error/ErrorCode.java'
--- src/main/java/com/akiban/server/error/ErrorCode.java	2013-04-15 14:38:06 +0000
+++ src/main/java/com/akiban/server/error/ErrorCode.java	2013-04-15 20:33:27 +0000
@@ -373,6 +373,8 @@
     INVALID_ROUTINE         ("50", "024", Importance.DEBUG, InvalidRoutineException.class),
     INVALID_INDEX_ID        ("50", "025", Importance.DEBUG, InvalidIndexIDException.class),
     MODEL_BUILDER_ERROR     ("50", "026", Importance.DEBUG, ModelBuilderException.class),
+    COLUMN_NOT_GENERATED    ("50", "027", Importance.DEBUG, ColumnNotGeneratedException.class),
+    COLUMN_ALREADY_GENERATED ("50", "028", Importance.DEBUG, ColumnAlreadyGeneratedException.class),
 
     // Class 51 - Internal problems created by user configuration
     STALE_AIS               ("51", "001", Importance.TRACE, OldAISException.class),

=== modified file 'src/main/java/com/akiban/server/service/dxl/BasicDDLFunctions.java'
--- src/main/java/com/akiban/server/service/dxl/BasicDDLFunctions.java	2013-04-11 18:35:20 +0000
+++ src/main/java/com/akiban/server/service/dxl/BasicDDLFunctions.java	2013-04-15 20:33:27 +0000
@@ -31,6 +31,7 @@
 
 import com.akiban.ais.model.AkibanInformationSchema;
 import com.akiban.ais.model.Column;
+import com.akiban.ais.model.DefaultNameGenerator;
 import com.akiban.ais.model.Group;
 import com.akiban.ais.model.GroupIndex;
 import com.akiban.ais.model.Index;
@@ -752,7 +753,7 @@
         for (Sequence sequence : schema.getSequences().values()) {
             // Drop the sequences in this schema, but not the 
             // generator sequences, which will be dropped with the table. 
-            if (!(sequence.getSequenceName().getTableName().startsWith("_sequence-"))) {
+            if (!(sequence.getSequenceName().getTableName().startsWith(DefaultNameGenerator.IDENTITY_SEQUENCE_PREFIX))) {
                 sequencesToDrop.add(sequence);
             }
         }

=== modified file 'src/main/java/com/akiban/sql/aisddl/AlterTableDDL.java'
--- src/main/java/com/akiban/sql/aisddl/AlterTableDDL.java	2013-03-22 20:05:57 +0000
+++ src/main/java/com/akiban/sql/aisddl/AlterTableDDL.java	2013-04-15 20:33:27 +0000
@@ -17,7 +17,10 @@
 
 package com.akiban.sql.aisddl;
 
+import com.akiban.ais.model.Sequence;
 import com.akiban.server.error.AkibanInternalException;
+import com.akiban.server.error.ColumnAlreadyGeneratedException;
+import com.akiban.server.error.ColumnNotGeneratedException;
 import com.akiban.sql.parser.AlterTableRenameColumnNode;
 import com.akiban.sql.parser.AlterTableRenameNode;
 import com.akiban.ais.AISCloner;
@@ -122,8 +125,7 @@
         List<ColumnDefinitionNode> columnDefNodes = new ArrayList<>();
         List<FKConstraintDefinitionNode> fkDefNodes= new ArrayList<>();
         List<ConstraintDefinitionNode> conDefNodes = new ArrayList<>();
-        List<String> newCols = null;
-        
+
         for(TableElementNode node : elements) {
             switch(node.getNodeType()) {
                 case NodeTypes.COLUMN_DEFINITION_NODE: {
@@ -181,7 +183,6 @@
                 } break;
 
                 case NodeTypes.AT_RENAME_NODE:
-                    
                     TableName newName = DDLHelper.convertName(defaultSchema,
                                                               ((AlterTableRenameNode)node).newName());
                     TableName oldName = table.getName();
@@ -189,18 +190,14 @@
                     return ChangeLevel.METADATA;
                     
                 case NodeTypes.AT_RENAME_COLUMN_NODE:
-
                     AlterTableRenameColumnNode alterRenameCol = (AlterTableRenameColumnNode) node;
                     String oldColName = alterRenameCol.getName();
                     String newColName = alterRenameCol.newName();
                     final Column oldCol = table.getColumn(oldColName);
                     if (oldCol == null)
                         throw new NoSuchColumnException(oldColName);
-                    if (newCols == null)
-                        newCols = new ArrayList<>();
-                    newCols.add(newColName);
                     columnChanges.add(TableChange.createModify(oldColName, newColName));
-                    break;
+                break;
 
                 default:
                     return null; // Something unsupported
@@ -216,38 +213,11 @@
         for(ColumnDefinitionNode cdn : columnDefNodes) {
             if(cdn instanceof ModifyColumnNode) {
                 ModifyColumnNode modNode = (ModifyColumnNode) cdn;
-                Column column = tableCopy.getColumn(modNode.getColumnName());
-                if(column == null) {
-                    throw new NoSuchColumnException(modNode.getColumnName());
-                }
-                switch(modNode.getNodeType()) {
-                    case NodeTypes.MODIFY_COLUMN_DEFAULT_NODE:
-                        column.setDefaultValue(TableDDL.getColumnDefault(modNode));
-                    break;
-                    case NodeTypes.MODIFY_COLUMN_CONSTRAINT_NODE: // Type only comes from NULL
-                        column.setNullable(true);
-                    break;
-                    case NodeTypes.MODIFY_COLUMN_CONSTRAINT_NOT_NULL_NODE: // Type only comes from NOT NULL
-                        column.setNullable(false);
-                    break;
-                    case NodeTypes.MODIFY_COLUMN_TYPE_NODE:
-                        tableCopy.dropColumn(modNode.getColumnName());
-                        TableDDL.addColumn(builder, table.getName().getSchemaName(), table.getName().getTableName(),
-                                           column.getName(), column.getPosition(), cdn.getType(), column.getNullable(),
-                                           column.getInitialAutoIncrementValue() != null,
-                                           column.getDefaultValue());
-                    break;
-                    default:
-                        throw new IllegalStateException("Unexpected node type: " + modNode);
-                }
+                handleModifyColumnNode(modNode, builder, tableCopy);
             } else {
                 TableDDL.addColumn(builder, cdn, table.getName().getSchemaName(), table.getName().getTableName(), pos++);
             }
         }
-        if (newCols != null)
-            for (String name : newCols)
-                if (tableCopy.getColumn(name) == null)
-                    throw new AkibanInternalException("New Columns " + newCols + " not created successfully");
         copyTableIndexes(table, tableCopy, columnChanges, indexChanges);
 
         IndexNameGenerator indexNamer = DefaultIndexNameGenerator.forTable(tableCopy);
@@ -283,6 +253,77 @@
         return ddl.alterTable(session, table.getName(), tableCopy, columnChanges, indexChanges, context);
     }
 
+    private static void handleModifyColumnNode(ModifyColumnNode modNode, AISBuilder builder, UserTable tableCopy) {
+        AkibanInformationSchema aisCopy = tableCopy.getAIS();
+        Column column = tableCopy.getColumn(modNode.getColumnName());
+        if(column == null) {
+            throw new NoSuchColumnException(modNode.getColumnName());
+        }
+        switch(modNode.getNodeType()) {
+            case NodeTypes.MODIFY_COLUMN_DEFAULT_NODE:
+                if(modNode.isAutoincrementColumn()) {
+                    int autoIncType = (int)modNode.getAutoinc_create_or_modify_Start_Increment();
+                    switch(autoIncType) {
+                        case ColumnDefinitionNode.CREATE_AUTOINCREMENT: {
+                            if(column.getIdentityGenerator() != null) {
+                                throw new ColumnAlreadyGeneratedException(column);
+                            }
+                            TableName name = tableCopy.getName();
+                            TableDDL.setAutoIncrement(builder, name.getSchemaName(), name.getTableName(), modNode);
+                        }
+                        break;
+                        case ColumnDefinitionNode.MODIFY_AUTOINCREMENT_INC_VALUE: {
+                            Sequence curSeq = column.getIdentityGenerator();
+                            if(curSeq == null) {
+                                throw new ColumnNotGeneratedException(column);
+                            }
+                            aisCopy.removeSequence(curSeq.getSequenceName());
+                            Sequence newSeq = Sequence.create(aisCopy,
+                                                              curSeq.getSchemaName(),
+                                                              curSeq.getSequenceName().getTableName(),
+                                                              curSeq.getStartsWith(),
+                                                              modNode.getAutoincrementIncrement(),
+                                                              curSeq.getMinValue(),
+                                                              curSeq.getMaxValue(),
+                                                              curSeq.isCycle());
+                            aisCopy.addSequence(newSeq);
+                            column.setIdentityGenerator(newSeq);
+                        }
+                        break;
+                        case ColumnDefinitionNode.MODIFY_AUTOINCREMENT_RESTART_VALUE:
+                            // Requires Accumulator reset
+                            throw new UnsupportedSQLException("Not yet implemented", modNode);
+                        default:
+                            throw new IllegalStateException("Unknown autoIncType: " + autoIncType);
+                    }
+                } else {
+                    // DROP DEFAULT will come though as a NULL default, clears both GENERATED and DEFAULT
+                    Sequence seq = column.getIdentityGenerator();
+                    if(seq != null) {
+                        column.setDefaultIdentity(null);
+                        column.setIdentityGenerator(null);
+                        aisCopy.removeSequence(seq.getSequenceName());
+                    }
+                    column.setDefaultValue(TableDDL.getColumnDefault(modNode));
+                }
+            break;
+            case NodeTypes.MODIFY_COLUMN_CONSTRAINT_NODE: // Type only comes from NULL
+                column.setNullable(true);
+            break;
+            case NodeTypes.MODIFY_COLUMN_CONSTRAINT_NOT_NULL_NODE: // Type only comes from NOT NULL
+                column.setNullable(false);
+            break;
+            case NodeTypes.MODIFY_COLUMN_TYPE_NODE:
+                tableCopy.dropColumn(modNode.getColumnName());
+                TableDDL.addColumn(builder, tableCopy.getName().getSchemaName(), tableCopy.getName().getTableName(),
+                                   column.getName(), column.getPosition(), modNode.getType(), column.getNullable(),
+                                   column.getDefaultValue());
+            break;
+            default:
+                throw new IllegalStateException("Unexpected node type: " + modNode);
+        }
+    }
+
     private static void checkColumnChange(UserTable table, String columnName) {
         Column column = table.getColumn(columnName);
         if(column == null) {

=== modified file 'src/main/java/com/akiban/sql/aisddl/TableDDL.java'
--- src/main/java/com/akiban/sql/aisddl/TableDDL.java	2013-04-11 05:21:42 +0000
+++ src/main/java/com/akiban/sql/aisddl/TableDDL.java	2013-04-15 20:33:27 +0000
@@ -213,7 +213,7 @@
             // BIGINT NOT NULL 
             DataTypeDescriptor bigint = new DataTypeDescriptor (TypeId.BIGINT_ID, false);
             addColumn (builder, schemaName, tableName, cdn.getColumnName(), colpos,
-                    bigint, false, true, getColumnDefault(cdn));
+                    bigint, false, getColumnDefault(cdn));
             // GENERATED ALWAYS AS IDENTITY
             setAutoIncrement (builder, schemaName, tableName, cdn.getColumnName(), false, 1, 1);
             // UNIQUE (KEY)
@@ -221,24 +221,25 @@
             builder.index(schemaName, tableName, cdn.getColumnName(), true, constraint);
             builder.indexColumn(schemaName, tableName, cdn.getColumnName(), cdn.getColumnName(), 0, true, null);
         } else {
-            boolean autoIncrement = cdn.isAutoincrementColumn();
-            
             addColumn(builder, schemaName, tableName, cdn.getColumnName(), colpos,
-                      cdn.getType(), cdn.getType().isNullable(), autoIncrement, getColumnDefault(cdn));
+                      cdn.getType(), cdn.getType().isNullable(), getColumnDefault(cdn));
            
-            if (autoIncrement) {
-                // if the cdn has a default node-> GENERATE BY DEFAULT
-                // if no default node -> GENERATE ALWAYS
-                Boolean defaultIdentity = cdn.getDefaultNode() != null;
-                setAutoIncrement (builder, schemaName, tableName, cdn.getColumnName(),
-                        defaultIdentity, cdn.getAutoincrementStart(), cdn.getAutoincrementIncrement());
+            if (cdn.isAutoincrementColumn()) {
+                setAutoIncrement(builder, schemaName, tableName, cdn);
             }
         }
     }
 
-    static void setAutoIncrement (final AISBuilder builder, 
-            String schemaName, String tableName, String columnName, boolean defaultIdentity, 
-            long start, long increment) {
+    public static void setAutoIncrement(AISBuilder builder, String schema, String table, ColumnDefinitionNode cdn) {
+        // if the cdn has a default node-> GENERATE BY DEFAULT
+        // if no default node -> GENERATE ALWAYS
+        Boolean defaultIdentity = cdn.getDefaultNode() != null;
+        setAutoIncrement(builder, schema, table, cdn.getColumnName(),
+                         defaultIdentity, cdn.getAutoincrementStart(), cdn.getAutoincrementIncrement());
+    }
+
+    public static void setAutoIncrement(AISBuilder builder, String schemaName, String tableName, String columnName,
+                                        boolean defaultIdentity, long start, long increment) {
         // The merge process will generate a real sequence name
         final String sequenceName = "temp-sequence-1"; 
         builder.sequence(schemaName, sequenceName, 
@@ -267,7 +268,7 @@
 
     static void addColumn(final AISBuilder builder,
                           final String schemaName, final String tableName, final String columnName,
-                          int colpos, DataTypeDescriptor type, boolean nullable, boolean autoIncrement,
+                          int colpos, DataTypeDescriptor type, boolean nullable,
                           final String defaultValue) {
         Long[] typeParameters = new Long[2];
         Type builderType = columnType(type, typeParameters, schemaName, tableName, columnName);
@@ -280,7 +281,7 @@
                        colpos,
                        builderType.name(), typeParameters[0], typeParameters[1],
                        nullable,
-                       autoIncrement,
+                       false,
                        charset, collation,
                        defaultValue);
     }

=== modified file 'src/main/java/com/akiban/sql/aisddl/ViewDDL.java'
--- src/main/java/com/akiban/sql/aisddl/ViewDDL.java	2013-03-22 20:05:57 +0000
+++ src/main/java/com/akiban/sql/aisddl/ViewDDL.java	2013-04-15 20:33:27 +0000
@@ -86,7 +86,7 @@
                 type = new DataTypeDescriptor(TypeId.CHAR_ID, true, 0);
             }
             TableDDL.addColumn(builder, schemaName, viewName, rc.getName(), colpos++,
-                               type, type.isNullable(), false, null);
+                               type, type.isNullable(), null);
         }
         View view = builder.akibanInformationSchema().getView(schemaName, viewName);
         ddlFunctions.createView(session, view);

=== modified file 'src/main/resources/com/akiban/server/error/error_code.properties'
--- src/main/resources/com/akiban/server/error/error_code.properties	2013-04-15 14:38:06 +0000
+++ src/main/resources/com/akiban/server/error/error_code.properties	2013-04-15 20:33:27 +0000
@@ -249,6 +249,8 @@
 INVALID_ROUTINE         = Invalid procedure `{0}.`{1}`: {2}
 INVALID_INDEX_ID        = Index `{0}.`{1}`.`{2}` has an invalid ID: {3}
 MODEL_BUILDER_ERROR     = Error building model for `{0}`.`{1}`: {2}
+COLUMN_NOT_GENERATED     = Column `{0}`.`{1}`.`{2}` is not generated
+COLUMN_ALREADY_GENERATED = Column `{0}`.`{1}`.`{2}` already generated by sequence `{3}`.`{4}`
 #
 # Class 51 - Internal problems created by user configuration
 #

=== modified file 'src/test/java/com/akiban/server/test/it/dxl/AlterTableBasicIT.java'
--- src/test/java/com/akiban/server/test/it/dxl/AlterTableBasicIT.java	2013-04-11 04:48:29 +0000
+++ src/test/java/com/akiban/server/test/it/dxl/AlterTableBasicIT.java	2013-04-15 20:33:27 +0000
@@ -21,6 +21,7 @@
 import com.akiban.ais.model.AISBuilder;
 import com.akiban.ais.model.AkibanInformationSchema;
 import com.akiban.ais.model.Column;
+import com.akiban.ais.model.DefaultNameGenerator;
 import com.akiban.ais.model.Index;
 import com.akiban.ais.model.Sequence;
 import com.akiban.ais.model.TableName;
@@ -1180,12 +1181,15 @@
         Sequence seq = column.getIdentityGenerator();
         assertNotNull("id column has sequence", seq);
 
-        AkibanInformationSchema copy = AISCloner.clone(ais());
-        copy.getUserTable(id).getColumn("id").setDefaultIdentity(false);
-        runAlter(ChangeLevel.METADATA, C_NAME, copy.getUserTable(id),
-                 Arrays.asList(TableChange.createModify("id", "id")), Arrays.<TableChange>asList());
+        runAlter(ChangeLevel.METADATA, "ALTER TABLE c ALTER COLUMN id DROP DEFAULT");
+        assertNull("Old seq was dropped", ais().getSequence(seq.getSequenceName()));
 
+        runAlter(ChangeLevel.METADATA, "ALTER TABLE c ALTER COLUMN id SET GENERATED ALWAYS AS IDENTITY");
         Column newColumn = getUserTable(id).getColumn("id");
         assertEquals("altered is always", false, newColumn.getDefaultIdentity());
+        seq = newColumn.getIdentityGenerator();
+        assertEquals("Sequence name prefix",
+                     true,
+                     seq.getSequenceName().getTableName().startsWith(DefaultNameGenerator.IDENTITY_SEQUENCE_PREFIX));
     }
 }

=== modified file 'src/test/java/com/akiban/sql/aisddl/AlterTableDDLTest.java'
--- src/test/java/com/akiban/sql/aisddl/AlterTableDDLTest.java	2013-03-22 20:05:57 +0000
+++ src/test/java/com/akiban/sql/aisddl/AlterTableDDLTest.java	2013-04-15 20:33:27 +0000
@@ -24,6 +24,7 @@
 import com.akiban.ais.model.IndexColumn;
 import com.akiban.ais.model.Join;
 import com.akiban.ais.model.JoinColumn;
+import com.akiban.ais.model.Sequence;
 import com.akiban.ais.model.TableName;
 import com.akiban.ais.model.UserTable;
 import com.akiban.ais.model.aisb2.AISBBasedBuilder;
@@ -31,6 +32,8 @@
 import com.akiban.ais.util.TableChange;
 import com.akiban.qp.operator.QueryContext;
 import com.akiban.server.api.ddl.DDLFunctionsMockBase;
+import com.akiban.server.error.ColumnAlreadyGeneratedException;
+import com.akiban.server.error.ColumnNotGeneratedException;
 import com.akiban.server.error.DuplicateColumnNameException;
 import com.akiban.server.error.DuplicateIndexException;
 import com.akiban.server.error.JoinColumnMismatchException;
@@ -42,6 +45,7 @@
 import com.akiban.server.error.NoSuchTableException;
 import com.akiban.server.error.NoSuchUniqueException;
 import com.akiban.server.error.UnsupportedCheckConstraintException;
+import com.akiban.server.error.UnsupportedSQLException;
 import com.akiban.server.service.session.Session;
 import com.akiban.server.types3.Types3Switch;
 import com.akiban.sql.StandardException;
@@ -208,7 +212,7 @@
         expectColumnChanges("ADD:new");
         expectIndexChanges();
         if (Types3Switch.ON) {
-            expectFinalTable(A_NAME, "aid MCOMPAT_ BIGINT(21) NOT NULL", "new MCOMPAT_ BIGINT(21) NOT NULL", "UNIQUE new(new)");
+            expectFinalTable(A_NAME, "aid MCOMPAT_ BIGINT(21) NOT NULL", "new MCOMPAT_ BIGINT(21) NOT NULL GENERATED ALWAYS AS IDENTITY (START WITH 1, INCREMENT BY 1)", "UNIQUE new(new)");
         } else {
             expectFinalTable(A_NAME, "aid bigint NOT NULL", "new bigint NOT NULL", "UNIQUE new(new)");
         }
@@ -221,7 +225,7 @@
         expectColumnChanges("ADD:new");
         expectIndexChanges("ADD:PRIMARY");
         if (Types3Switch.ON) {
-            expectFinalTable(A_NAME, "aid MCOMPAT_ BIGINT(21) NOT NULL", "new MCOMPAT_ BIGINT(21) NOT NULL", "UNIQUE new(new)", "PRIMARY(new)");
+            expectFinalTable(A_NAME, "aid MCOMPAT_ BIGINT(21) NOT NULL", "new MCOMPAT_ BIGINT(21) NOT NULL GENERATED ALWAYS AS IDENTITY (START WITH 1, INCREMENT BY 1)", "UNIQUE new(new)", "PRIMARY(new)");
         } else {
             expectFinalTable(A_NAME, "aid bigint NOT NULL", "new bigint NOT NULL", "UNIQUE new(new)", "PRIMARY(new)");
         }
@@ -540,6 +544,84 @@
     }
 
     //
+    // ALTER COLUMN DROP DEFAULT (where default is generated)
+    //
+    @Test
+    public void alterColumnDropDefaultGenerated() throws StandardException {
+        buildCWithGeneratedID(1, true);
+        parseAndRun("ALTER TABLE c ALTER COLUMN id DROP DEFAULT");
+        expectColumnChanges("MODIFY:id->id");
+        expectIndexChanges();
+        expectFinalTable(C_NAME, "id MCOMPAT_ INTEGER(11) NOT NULL", "PRIMARY(id)");
+    }
+
+    //
+    // ALTER COLUMN SET INCREMENT BY <number>
+    //
+
+    @Test
+    public void alterColumnSetIncrementByLess() throws StandardException {
+        buildCWithGeneratedID(1, true);
+        parseAndRun("ALTER TABLE c ALTER COLUMN id SET INCREMENT BY -1");
+        expectColumnChanges("MODIFY:id->id");
+        expectIndexChanges();
+        expectFinalTable(C_NAME, "id MCOMPAT_ INTEGER(11) NOT NULL GENERATED ALWAYS AS IDENTITY (START WITH 1, INCREMENT BY -1)", "PRIMARY(id)");
+    }
+
+    @Test
+    public void alterColumnSetIncrementByMore() throws StandardException {
+        buildCWithGeneratedID(1, true);
+        parseAndRun("ALTER TABLE c ALTER COLUMN id SET INCREMENT BY 5");
+        expectColumnChanges("MODIFY:id->id");
+        expectIndexChanges();
+        expectFinalTable(C_NAME, "id MCOMPAT_ INTEGER(11) NOT NULL GENERATED ALWAYS AS IDENTITY (START WITH 1, INCREMENT BY 5)", "PRIMARY(id)");
+    }
+
+    @Test(expected=ColumnNotGeneratedException.class)
+    public void alterColumnSetIncrementInvalid() throws StandardException {
+        buildCWithID();
+        parseAndRun("ALTER TABLE c ALTER COLUMN id SET INCREMENT BY 5");
+    }
+
+    //
+    // ALTER COLUMN RESTART WITH <number>
+    //
+
+    @Test(expected=UnsupportedSQLException.class)
+    public void alterColumnRestartWith() throws StandardException {
+        buildCWithGeneratedID(1, true);
+        parseAndRun("ALTER TABLE c ALTER COLUMN id RESTART WITH 10");
+    }
+
+    //
+    // ALTER COLUMN [SET] GENERATED <BY DEFAULT | ALWAYS>
+    //
+
+    @Test
+    public void alterColumnSetGeneratedByDefault() throws StandardException {
+        buildCWithID();
+        parseAndRun("ALTER TABLE c ALTER COLUMN id SET GENERATED BY DEFAULT AS IDENTITY (START WITH 10, INCREMENT BY 50)");
+        expectColumnChanges("MODIFY:id->id");
+        expectIndexChanges();
+        expectFinalTable(C_NAME, "id MCOMPAT_ INTEGER(11) NOT NULL GENERATED BY DEFAULT AS IDENTITY (START WITH 10, INCREMENT BY 50)", "PRIMARY(id)");
+    }
+
+    @Test
+    public void alterColumnSetGeneratedAlways() throws StandardException {
+        buildCWithID();
+        parseAndRun("ALTER TABLE c ALTER COLUMN id SET GENERATED ALWAYS AS IDENTITY (START WITH 42, INCREMENT BY 100)");
+        expectColumnChanges("MODIFY:id->id");
+        expectIndexChanges();
+        expectFinalTable(C_NAME, "id MCOMPAT_ INTEGER(11) NOT NULL GENERATED ALWAYS AS IDENTITY (START WITH 42, INCREMENT BY 100)", "PRIMARY(id)");
+    }
+
+    @Test(expected=ColumnAlreadyGeneratedException.class)
+    public void alterColumnSetGeneratedAlreadyGenerated() throws StandardException {
+        buildCWithGeneratedID(1, true);
+        parseAndRun("ALTER TABLE c ALTER COLUMN id SET GENERATED ALWAYS AS IDENTITY (START WITH 42, INCREMENT BY 100)");
+    }
+
+    //
     // ADD [CONSTRAINT] UNIQUE
     //
 
@@ -1155,6 +1237,14 @@
         builder.userTable(A_NAME).colBigInt("id", false).colBigInt("other_id", true).pk("id");
     }
 
+    private void buildCWithGeneratedID(int startWith, boolean always) {
+        builder.userTable(C_NAME).autoIncLong("id", startWith, always).pk("id");
+    }
+
+    private void buildCWithID() {
+        builder.userTable(C_NAME).colLong("id", false).pk("id");
+    }
+
     private static class DDLFunctionsMock extends DDLFunctionsMockBase {
         final AkibanInformationSchema ais;
         final List<String> columnChangeDesc = new ArrayList<>();
@@ -1212,6 +1302,17 @@
                 sb.append(" DEFAULT ");
                 sb.append(defaultVal);
             }
+            Boolean identity = col.getDefaultIdentity();
+            if(identity != null) {
+                Sequence seq = col.getIdentityGenerator();
+                sb.append(" GENERATED ");
+                sb.append(identity ? "BY DEFAULT" : "ALWAYS");
+                sb.append(" AS IDENTITY (START WITH ");
+                sb.append(seq.getStartsWith());
+                sb.append(", INCREMENT BY ");
+                sb.append(seq.getIncrement());
+                sb.append(')');
+            }
         }
         for(Index index : table.getIndexes()) {
             sb.append(", ");

=== modified file 'src/test/java/com/akiban/sql/aisddl/TableDDLIT.java'
--- src/test/java/com/akiban/sql/aisddl/TableDDLIT.java	2013-04-11 05:21:42 +0000
+++ src/test/java/com/akiban/sql/aisddl/TableDDLIT.java	2013-04-15 20:33:27 +0000
@@ -106,7 +106,7 @@
         assertNotNull(table);
         assertEquals(table.getColumn(0).getType(), Types.INT);
         assertEquals(table.getPrimaryKey().getColumns().get(0), table.getColumn(0));
-        assertEquals(1000L, table.getColumn(0).getInitialAutoIncrementValue().longValue());
+        assertEquals(1000L, table.getColumn(0).getIdentityGenerator().getStartsWith());
     }
 
     @Test

=== modified file 'src/test/resources/com/akiban/sql/pg/yaml/functional/test-identity.yaml'
--- src/test/resources/com/akiban/sql/pg/yaml/functional/test-identity.yaml	2012-09-26 03:50:12 +0000
+++ src/test/resources/com/akiban/sql/pg/yaml/functional/test-identity.yaml	2013-04-15 20:33:27 +0000
@@ -146,4 +146,17 @@
 ---
 - Statement: select * from t
 - output: [[1, 1, null]]
+---
+- DropTable: t
+
+---
+- CreateTable: t (id int not null primary key)
+---
+- Statement: ALTER TABLE t ALTER COLUMN id SET GENERATED BY DEFAULT AS IDENTITY (START WITH 42, INCREMENT BY 5)
+---
+- Statement: INSERT INTO t VALUES (NULL),(NULL),(NULL)
+---
+- Statement: SELECT * FROM t
+- output: [[42],[47],[52]]
+
 ...