Resolve some MySQL compatibility issues

h2/src/docsrc/html/changelog.html

@@ -21,6 +21,12 @@ <h1>Change Log</h1>
 
 <h2>Next Version (unreleased)</h2>
 <ul>
+<li>Issue #1942: MySQL Mode: convertInsertNullToZero should be turned off by default?
+</li>
+<li>Issue #1940: MySQL Mode: Modify column from NOT NULL to NULL syntax
+</li>
+<li>PR #1941: Extract OFFSET / FETCH handling from Select and SelectUnion to Query
+</li>
 <li>Issue #1938: Regression with CREATE OR REPLACE VIEW. Causes "Duplicate column name" exception.
 </li>
 <li>PR #1937: Get rid of FunctionCursorResultSet

h2/src/docsrc/html/features.html

@@ -903,11 +903,7 @@ <h3>MySQL Compatibility Mode</h3>
 When case-insensitive identifiers are needed append <code>;CASE_INSENSITIVE_IDENTIFIERS=TRUE</code> to URL.
 Do not change value of DATABASE_TO_LOWER after creation of database.
 </p>
-<ul><li>When inserting data, if a column is defined to be <code>NOT NULL</code>
-    and <code>NULL</code> is inserted,
-    then a 0 (or empty string, or the current timestamp for timestamp columns) value is used.
-    Usually, this operation is not allowed and an exception is thrown.
-</li><li>Creating indexes in the <code>CREATE TABLE</code> statement is allowed using
+<ul><li>Creating indexes in the <code>CREATE TABLE</code> statement is allowed using
     <code>INDEX(..)</code> or <code>KEY(..)</code>.
     Example: <code>create table test(id int primary key, name varchar(255), key idx_name(name));</code>
 </li><li>When converting a floating point number to an integer, the fractional

h2/src/main/org/h2/command/Parser.java

@@ -7593,7 +7593,8 @@ private Prepared parseAlterTable() {
                 }
                 break;
             case NO_NULL_CONSTRAINT_FOUND:
-                command = parseAlterTableAlterColumnType(schema, tableName, columnName, ifTableExists);
+                command = parseAlterTableAlterColumnType(schema, tableName, columnName, ifTableExists,
+                        database.getMode().getEnum() != ModeEnum.MySQL);
                 break;
             default:
                 throw DbException.get(ErrorCode.UNKNOWN_MODE_1,
@@ -7704,7 +7705,7 @@ private Prepared parseAlterTable() {
                 command.setSelectivity(readExpression());
                 return command;
             } else {
-                return parseAlterTableAlterColumnType(schema, tableName, columnName, ifTableExists);
+                return parseAlterTableAlterColumnType(schema, tableName, columnName, ifTableExists, true);
             }
         } else if (database.getMode().getEnum() == ModeEnum.MySQL && readIf("AUTO_INCREMENT")) {
             readIf(EQUAL);
@@ -7758,10 +7759,10 @@ private Prepared commandIfTableExists(Schema schema, String tableName,
     }
 
     private AlterTableAlterColumn parseAlterTableAlterColumnType(Schema schema,
-            String tableName, String columnName, boolean ifTableExists) {
+            String tableName, String columnName, boolean ifTableExists, boolean preserveNotNull) {
         Column oldColumn = columnIfTableExists(schema, tableName, columnName, ifTableExists);
         Column newColumn = parseColumnForTable(columnName,
-                oldColumn == null ? true : oldColumn.isNullable(), true);
+                !preserveNotNull || oldColumn == null || oldColumn.isNullable(), true);
         if (readIf(CHECK)) {
             Expression expr = readExpression();
             newColumn.addCheckConstraint(session, expr);

h2/src/main/org/h2/engine/Mode.java

@@ -60,14 +60,6 @@ public enum UniqueIndexNullsHandling {
      */
     public boolean aliasColumnName;
 
-    /**
-     * When inserting data, if a column is defined to be NOT NULL and NULL is
-     * inserted, then a 0 (or empty string, or the current timestamp for
-     * timestamp columns) value is used. Usually, this operation is not allowed
-     * and an exception is thrown.
-     */
-    public boolean convertInsertNullToZero;
-
     /**
      * When converting the scale of decimal data, the number is only converted
      * if the new scale is smaller than the current scale. Usually, the scale is
@@ -299,7 +291,6 @@ public enum UniqueIndexNullsHandling {
         add(mode);
 
         mode = new Mode(ModeEnum.MySQL);
-        mode.convertInsertNullToZero = true;
         mode.indexDefinitionInCreateTable = true;
         mode.lowerCaseIdentifiers = true;
         // Next one is for MariaDB

h2/src/main/org/h2/table/Column.java

@@ -29,11 +29,8 @@
 import org.h2.value.DataType;
 import org.h2.value.TypeInfo;
 import org.h2.value.Value;
-import org.h2.value.ValueInt;
 import org.h2.value.ValueLong;
 import org.h2.value.ValueNull;
-import org.h2.value.ValueString;
-import org.h2.value.ValueTime;
 import org.h2.value.ValueUuid;
 
 /**
@@ -398,25 +395,7 @@ public Value validateConvertUpdateSequence(Session session, Value value) {
                 }
             }
             if (value == ValueNull.INSTANCE && !nullable) {
-                if (mode.convertInsertNullToZero) {
-                    int t = type.getValueType();
-                    DataType dt = DataType.getDataType(t);
-                    if (dt.decimal) {
-                        value = ValueInt.get(0).convertTo(t);
-                    } else if (dt.type == Value.TIMESTAMP) {
-                        value = session.getCurrentCommandStart().convertTo(Value.TIMESTAMP);
-                    } else if (dt.type == Value.TIMESTAMP_TZ) {
-                        value = session.getCurrentCommandStart();
-                    } else if (dt.type == Value.TIME) {
-                        value = ValueTime.fromNanos(0);
-                    } else if (dt.type == Value.DATE) {
-                        value = session.getCurrentCommandStart().convertTo(Value.DATE);
-                    } else {
-                        value = ValueString.get("").convertTo(t);
-                    }
-                } else {
-                    throw DbException.get(ErrorCode.NULL_NOT_ALLOWED, name);
-                }
+                throw DbException.get(ErrorCode.NULL_NOT_ALLOWED, name);
             }
         }
         if (checkConstraint != null) {

h2/src/test/org/h2/test/scripts/ddl/alterTableAlterColumn.sql

@@ -121,3 +121,50 @@ SET MODE Regular;
 
 DROP TABLE TEST;
 > ok
+
+-- Compatibility syntax
+
+CREATE MEMORY TABLE TEST(V INT NOT NULL);
+> ok
+
+ALTER TABLE TEST MODIFY COLUMN V BIGINT;
+> ok
+
+SCRIPT NODATA NOPASSWORDS NOSETTINGS TABLE TEST;
+> SCRIPT
+> -----------------------------------------------------------
+> -- 0 +/- SELECT COUNT(*) FROM PUBLIC.TEST;
+> CREATE MEMORY TABLE "PUBLIC"."TEST"( "V" BIGINT NOT NULL );
+> CREATE USER IF NOT EXISTS "SA" PASSWORD '' ADMIN;
+> rows: 3
+
+SET MODE MySQL;
+> ok
+
+ALTER TABLE TEST MODIFY COLUMN V INT;
+> ok
+
+SCRIPT NODATA NOPASSWORDS NOSETTINGS TABLE TEST;
+> SCRIPT
+> -------------------------------------------------
+> -- 0 +/- SELECT COUNT(*) FROM PUBLIC.TEST;
+> CREATE MEMORY TABLE "PUBLIC"."TEST"( "V" INT );
+> CREATE USER IF NOT EXISTS "SA" PASSWORD '' ADMIN;
+> rows: 3
+
+ALTER TABLE TEST MODIFY COLUMN V BIGINT NOT NULL;
+> ok
+
+SCRIPT NODATA NOPASSWORDS NOSETTINGS TABLE TEST;
+> SCRIPT
+> -----------------------------------------------------------
+> -- 0 +/- SELECT COUNT(*) FROM PUBLIC.TEST;
+> CREATE MEMORY TABLE "PUBLIC"."TEST"( "V" BIGINT NOT NULL );
+> CREATE USER IF NOT EXISTS "SA" PASSWORD '' ADMIN;
+> rows: 3
+
+SET MODE Regular;
+> ok
+
+DROP TABLE TEST;
+> ok