README.md in embulk-output-redshift-0.3.0 vs README.md in embulk-output-redshift-0.4.0

@@ -18,16 +18,16 @@
 - **schema**: destination schema name (string, default: "public")
 - **table**: destination table name (string, required)
 - **options**: extra connection properties (hash, default: {})
 - **mode**: "replace" or "insert" (string, required)
 - **batch_size**: size of a single batch insert (integer, default: 16777216)
-- **default_timezone**: If input column type (embulk type) is timestamp and destination column type is `string` or `nstring`, this plugin needs to format the timestamp into a string. This default_timezone option is used to control the timezone. You can overwrite timezone for each columns using column_options option. (string, default: `UTC`)
+- **default_timezone**: If input column type (embulk type) is timestamp, this plugin needs to format the timestamp into a SQL string. This default_timezone option is used to control the timezone. You can overwrite timezone for each columns using column_options option. (string, default: `UTC`)
 - **column_options**: advanced: a key-value pairs where key is a column name and value is options for the column.
   - **type**: type of a column when this plugin creates new tables (e.g. `VARCHAR(255)`, `INTEGER NOT NULL UNIQUE`). This used when this plugin creates intermediate tables (insert, truncate_insert and merge modes), when it creates the target table (insert_direct and replace modes), and when it creates nonexistent target table automatically. (string, default: depends on input column type. `BIGINT` if input column type is long, `BOOLEAN` if boolean, `DOUBLE PRECISION` if double, `CLOB` if string, `TIMESTAMP` if timestamp)
   - **value_type**: This plugin converts input column type (embulk type) into a database type to build a INSERT statement. This value_type option controls the type of the value in a INSERT statement. (string, default: depends on input column type. Available values options are: `byte`, `short`, `int`, `long`, `double`, `float`, `boolean`, `string`, `nstring`, `date`, `time`, `timestamp`, `decimal`, `null`, `pass`)
   - **timestamp_format**: If input column type (embulk type) is timestamp and value_type is `string` or `nstring`, this plugin needs to format the timestamp value into a string. This timestamp_format option is used to control the format of the timestamp. (string, default: `%Y-%m-%d %H:%M:%S.%6N`)
-  - **timezone**: If input column type (embulk type) is timestamp and value_type is `string` or `nstring`, this plugin needs to format the timestamp value into a string. And if the input column type is timestamp and value_type is `date`, this plugin needs to consider timezone. In those cases, this timezone option is used to control the timezone. (string, value of default_timezone option is used by default)
+  - **timezone**: If input column type (embulk type) is timestamp, this plugin needs to format the timestamp value into a SQL string. In this cases, this timezone option is used to control the timezone. (string, value of default_timezone option is used by default)
 
 ### Modes
 
 * **insert**:
   * Behavior: This mode writes rows to some intermediate tables first. If all those tasks run correctly, runs `INSERT INTO <target_table> SELECT * FROM <intermediate_table_1> UNION ALL SELECT * FROM <intermediate_table_2> UNION ALL ...` query.
@@ -40,10 +40,10 @@
 * **truncate_insert**:
   * Behavior: Same with `insert` mode excepting that it truncates the target table right before the last `INSERT ...` query.
   * Transactional: Yes.
   * Resumable: Yes.
 * **merge**:
-  * Behavior: This mode writes rows to some intermediate tables first. If all those tasks run correctly, runs `INSERT INTO <target_table> SELECT * FROM <intermediate_table_1> UNION ALL SELECT * FROM <intermediate_table_2> UNION ALL ... ON DUPLICATE KEY UPDATE ...` query.
+  * Behavior: This mode writes rows to some intermediate tables first. If all those tasks run correctly, runs `with updated AS (UPDATE .... RETURNING ...) INSERT INTO ....` query.
   * Transactional: Yes.
   * Resumable: Yes.
 * **replace**:
   * Behavior: Same with `insert` mode excepting that it truncates the target table right before the last `INSERT ...` query.
   * Transactional: Yes.