feat: generate default clause when table column NULL is changed (#250)

If a column with a DEFAULT value has its NOT NULL clause added or removed, the DEFAULT clause also needs to be in the ALTER statement otherwise the DEFAULT clause is dropped.

Co-authored-by: Niel Markwick <nielm@google.com>

Author: gurminder71

src/main/java/com/google/cloud/solutions/spannerddl/diff/DdlDiff.java

@@ -611,11 +611,13 @@ private static void addColumnDiffs(
     }
 
     // Not null or type length limit change.
+    boolean notNullOrTypeChanged;
     if (columnDiff.leftValue().isNotNull() != columnDiff.rightValue().isNotNull()
         || !columnDiff
             .leftValue()
             .getColumnTypeString()
             .equals(columnDiff.rightValue().getColumnTypeString())) {
+      notNullOrTypeChanged = true;
       alterStatements.add(
           Joiner.on(" ")
               .skipNulls()
@@ -625,7 +627,10 @@ private static void addColumnDiffs(
                   "ALTER COLUMN",
                   columnDiff.rightValue().getColumnName(),
                   columnDiff.rightValue().getColumnTypeString(),
-                  (columnDiff.rightValue().isNotNull() ? "NOT NULL" : null)));
+                  (columnDiff.rightValue().isNotNull() ? "NOT NULL" : null),
+                  columnDiff.rightValue().getColumnDefaultClause()));
+    } else {
+      notNullOrTypeChanged = false;
     }
 
     // Update options.
@@ -649,7 +654,7 @@ private static void addColumnDiffs(
         columnDiff.leftValue().getColumnDefaultClause();
     final ASTcolumn_default_clause newDefaultValue =
         columnDiff.rightValue().getColumnDefaultClause();
-    if (!Objects.equals(oldDefaultValue, newDefaultValue)) {
+    if (!notNullOrTypeChanged && !Objects.equals(oldDefaultValue, newDefaultValue)) {
       if (newDefaultValue == null) {
         alterStatements.add(
             "ALTER TABLE "

src/test/resources/expectedDdlDiff.txt

@@ -379,5 +379,14 @@ ALTER TABLE mytable SET OPTIONS (locality_group='lg2')
 
 ALTER TABLE mytable SET OPTIONS (droppedKey=NULL,newKey='value2')
 
+== test 75 column changing not null with default value
+ALTER TABLE test ALTER COLUMN add_nn BOOL NOT NULL DEFAULT (FALSE)
+ALTER TABLE test ALTER COLUMN add_both BOOL NOT NULL DEFAULT (FALSE)
+ALTER TABLE test ALTER COLUMN remove_NN BOOL DEFAULT (FALSE)
+ALTER TABLE test ALTER COLUMN remove_def DROP DEFAULT
+ALTER TABLE test ALTER COLUMN remove_both BOOL
+ALTER TABLE test ALTER COLUMN change_both BOOL NOT NULL DEFAULT (TRUE)
+ALTER TABLE test ALTER COLUMN change_def SET DEFAULT (TRUE)
+
 ==
 

src/test/resources/newDdl.txt

@@ -592,4 +592,18 @@ create table mytable (keycol int64) primary key(keycol), OPTIONS(locality_group
 
 create table mytable (keycol int64) primary key(keycol), OPTIONS(existingKey='value', newKey='value2')
 
+== test 75 column changing not null with default value
+
+CREATE TABLE test (
+  id STRING(36),
+  add_nn BOOL NOT NULL DEFAULT (FALSE),
+  add_both BOOL NOT NULL DEFAULT (FALSE),
+  remove_NN BOOL DEFAULT(FALSE),
+  remove_def BOOL NOT NULL,
+  remove_both BOOL,
+  change_def BOOL NOT NULL DEFAULT (TRUE),
+  change_both BOOL NOT NULL DEFAULT (TRUE),
+) PRIMARY KEY (id)
+
+
 ==

src/test/resources/originalDdl.txt

@@ -591,5 +591,18 @@ create table mytable (keycol int64) primary key(keycol), OPTIONS(locality_group
 
 create table mytable (keycol int64) primary key(keycol), OPTIONS(existingKey='value', droppedKey='value1')
 
+== test 75 column changing not null with default value
+
+CREATE TABLE test (
+  id STRING(36),
+  add_nn BOOL DEFAULT (FALSE),
+  add_both BOOL,
+  remove_NN BOOL NOT NULL DEFAULT(FALSE),
+  remove_def BOOL NOT NULL DEFAULT(FALSE),
+  remove_both BOOL NOT NULL DEFAULT(FALSE),
+  change_both BOOL DEFAULT (FALSE),
+  change_def BOOL NOT NULL DEFAULT (FALSE),
+) PRIMARY KEY (id)
+
 ==