Amazon Redshift publicizes historical past mode for zero-ETL integrations to simplify historic knowledge monitoring and evaluation

Within the ever-evolving panorama of cloud computing and knowledge administration, AWS has constantly been on the forefront of innovation. One of many groundbreaking developments lately is zero-ETL integration, a set of absolutely managed integrations by AWS that minimizes the necessity to construct extract, remodel, and cargo (ETL) knowledge pipelines. This publish will discover temporary historical past of zero-ETL, its significance for patrons, and introduce an thrilling new characteristic: historical past mode for Amazon Aurora PostgreSQL-Suitable Version, Amazon Aurora MySQL-Suitable Version, Amazon Relational Database Service (Amazon RDS) for MySQL, and Amazon DynamoDB zero-ETL integration with Amazon Redshift.

A quick historical past of zero-ETL integrations

The idea of zero-ETL integrations emerged as a response to the rising complexities and inefficiencies in conventional ETL processes. Conventional ETL processes are time-consuming and complicated to develop, keep, and scale. Though not all use circumstances might be changed with zero-ETL, it simplifies the replication and means that you can apply transformation post-replication. This eliminates the necessity for extra ETL expertise between the supply database and Amazon Redshift. We at AWS acknowledged the necessity for a extra streamlined method to knowledge integration, notably between operational databases and the cloud knowledge warehouses. The journey of zero-ETL started in late 2022 after we launched the characteristic for Aurora MySQL with Amazon Redshift. This characteristic marked a pivotal second in streamlining advanced knowledge workflows, enabling close to real-time knowledge replication and evaluation whereas eliminating the necessity for ETL processes.

Constructing on the success of our first zero-ETL integration, we’ve made steady strides on this area by working backward from our clients’ wants and launching options like knowledge filtering, auto and incremental refresh of materialized views, refresh interval, and extra. Moreover, we elevated the breadth of sources to incorporate Aurora PostgreSQL, DynamoDB, and Amazon RDS for MySQL to Amazon Redshift integrations, solidifying our dedication to creating it seamless so that you can run analytics in your knowledge. The introduction of zero-ETL was not only a technological development; it represented a paradigm shift in how organizations may method their knowledge methods. By eradicating the necessity for intermediate knowledge processing steps, we opened up new potentialities for close to real-time analytics and decision-making.

Introducing historical past mode: A brand new frontier in knowledge evaluation

Zero-ETL has already simplified the information integration, and we’re excited to additional improve the capabilities by asserting a brand new characteristic that takes it a step additional: historical past mode with Amazon Redshift. Utilizing historical past mode with zero-ETL integrations, you may streamline your historic knowledge evaluation by sustaining full change knowledge seize (CDC) from the supply in Amazon Redshift. Historical past mode lets you unlock the complete potential of your knowledge by seamlessly capturing and retaining historic variations of data throughout your zero-ETL knowledge sources. You’ll be able to carry out superior historic evaluation, construct look again experiences, carry out pattern evaluation, and create slowly altering dimensions (SCD) Sort 2 tables on Amazon Redshift. This lets you consolidate your core analytical belongings and derive insights throughout a number of functions, gaining price financial savings and operational efficiencies. Historical past mode permits organizations to adjust to regulatory necessities for sustaining historic data, facilitating complete knowledge governance and knowledgeable decision-making.

Zero-ETL integrations present a present view of data in close to actual time, that means solely the most recent modifications from supply databases are retained on Amazon Redshift. With historical past mode, Amazon Redshift introduces a revolutionary method to historic knowledge evaluation. Now you can configure your zero-ETL integrations to trace each model of your data in supply tables straight in Amazon Redshift, together with the supply timestamp with each file model indicating when every file was inserted, modified, or deleted. As a result of knowledge modifications are tracked and retained by Amazon Redshift, this can assist you meet your compliance necessities with out having to take care of duplicate copies in knowledge sources. As well as, you don’t have to take care of and handle partitioned tables to maintain older knowledge intact as separate partitions to model data, and keep historic knowledge in supply databases.

In an information warehouse, the most typical dimensional modeling methods is a star schema, the place there’s a truth desk on the heart surrounded by quite a few related dimension tables. A dimension is a construction that categorizes details and measures with a purpose to allow customers to reply enterprise questions. As an instance an instance, in a typical gross sales area, buyer, time, or product are dimensions and gross sales transactions is a truth. An SCD is an information warehousing idea that incorporates comparatively static knowledge that may change slowly over a time period. There are three main forms of SCDs maintained in knowledge warehousing: Sort 1 (no historical past), Sort 2 (full historical past), and Sort 3 (restricted historical past). CDC is a attribute of a database that gives a capability to determine the information that modified between two database hundreds, in order that an motion might be carried out on the modified knowledge.

On this publish, we reveal easy methods to allow historical past mode for tables in a zero-ETL integration and seize the complete historic knowledge modifications as SCD2.

Answer overview

On this use case, we discover how a fictional nationwide retail chain, AnyCompany, makes use of AWS providers to realize priceless insights into their buyer base. With a number of areas throughout the nation, AnyCompany goals to reinforce their understanding of buyer conduct and enhance their advertising and marketing methods by two key initiatives:

• Buyer migration evaluation – AnyCompany seeks to trace and analyze buyer relocation patterns, specializing in how geographical strikes influence buying conduct. By monitoring these modifications, the corporate can adapt its stock, providers, and native advertising and marketing efforts to raised serve clients of their new areas.
• Advertising marketing campaign effectiveness – The retailer desires to guage the influence of focused advertising and marketing campaigns based mostly on buyer demographics on the time of marketing campaign execution. This evaluation can assist AnyCompany refine its advertising and marketing methods, optimize useful resource allocation, and enhance general marketing campaign efficiency.

By carefully monitoring modifications in buyer profiles for each geographic motion and advertising and marketing responsiveness, AnyCompany is positioning itself to make extra knowledgeable, data-driven selections.

On this demonstration, we start by loading a pattern dataset into the supply desk, buyer, in Aurora PostgreSQL-Suitable. To keep up historic data, we allow historical past mode on the buyer desk, which robotically tracks modifications in Amazon Redshift.

When historical past mode is turned on, the next columns are robotically added to the goal desk, buyer, in Amazon Redshift to maintain observe of modifications within the supply.

Subsequent, we create a dimension desk, customer_dim, in Amazon Redshift with a further surrogate key column to indicate an instance of making an SCD desk. To optimize question efficiency for various queries, a few of which may be analyzing energetic or inactive data solely whereas different queries may be analyzing knowledge as of a sure date, we outlined the type key consisting of _record_is_active, _record_create_time, and _record_delete_time attributes within the customer_dim desk.

The next determine supplies the schema of the supply desk in Aurora PostgreSQL-Suitable, and the goal desk and goal buyer dimension desk in Amazon Redshift.

To streamline the information inhabitants course of, we developed a saved process named SP_Customer_Type2_SCD(). This process is designed to populate incremental knowledge into the customer_dim desk from the replicated buyer desk. It handles numerous knowledge modifications, together with updates, inserts, and deletes within the supply desk and implementing an SCD2 method.

Stipulations

Earlier than you get began, full the next steps:

1. Configure your Aurora DB cluster and your Redshift knowledge warehouse with the required parameters and permissions. For directions, discuss with Getting began with Aurora zero-ETL integrations with Amazon Redshift.
2. Create an Aurora zero-ETL integration with Amazon Redshift.
3. From an Amazon Elastic Compute Cloud (Amazon EC2) terminal or utilizing AWS CloudShell, SSH into the Aurora PostgreSQL cluster and run the next instructions to put in psql:

sudo dnf set up postgresql15
psql --version

4. Load the pattern supply knowledge:
   • Obtain the TPC-DS pattern dataset for the buyer desk onto the machine operating psql.
   • From the EC2 terminal, run the next command to hook up with the Aurora PostgreSQL DB utilizing the default tremendous consumer postgres:

     psql -h <RDS Write Occasion Endpoint> -p 5432 -U postgres

   • Run the next SQL command to create the database zetl:

     create database zetl template template1;

   • Change the connection to the newly created database:
   • Create the buyer desk (the next instance creates it within the public schema):

     CREATE TABLE buyer(
         c_customer_id char(16) NOT NULL PRIMARY KEY,
         c_salutation char(10),
         c_first_name char(20),
         c_last_name char(30),
         c_preferred_cust_flag char(1),
         c_birth_day int4,
         c_birth_month int4,
         c_birth_year int4,
         c_birth_country varchar(20),
         c_login char(13),
         c_email_address char(50),
         ca_street_number char(10),
         ca_street_name varchar(60),
         ca_street_type char(15),
         ca_suite_number char(10),
         ca_city varchar(60),
         ca_county varchar(30),
         ca_state char(2),
         ca_zip char(10),
         ca_country varchar(20),
         ca_gmt_offset numeric(5, 2),
         ca_location_type char(20)
     );

   • Run the next command to load buyer knowledge from the downloaded dataset after altering the highlighted location of the dataset to your listing path:

     copy buyer from '/house/ec2-user/customer_sample_data.dat' WITH DELIMITER '|' CSV;

   • Run the next question to validate the profitable creation of the desk and loading of pattern knowledge:

     SELECT table_catalog, table_schema, table_name, n_live_tup AS row_count
     FROM information_schema.tables JOIN g_stat_user_tables ON table_name = relname
     WHERE table_type="BASE TABLE"
     ORDER BY row_count DESC;

The SQL output needs to be as follows:

table_catalog | table_schema | table_name | row_count
---------------+--------------+------------+-----------
zetl          | public       | buyer   |   1200585
(1 row)

Create a goal database in Amazon Redshift

To duplicate knowledge out of your supply into Amazon Redshift, you could create a goal database out of your integration in Amazon Redshift. For this publish, now we have already created a supply database known as zetl in Aurora PostgreSQL-Suitable as a part of the stipulations. Full the next steps to create the goal database:

1. On the Amazon Redshift console, select Question editor v2 within the navigation pane.
2. Run the next instructions to create a database known as postgres in Amazon Redshift utilizing the zero-ETL integration_id with historical past mode turned on.

-- Amazon Redshift SQL instructions to create database
SELECT integration_id FROM svv_integration; -- copy this end result, use within the subsequent sql
CREATE DATABASE "postgres" FROM INTEGRATION '<end result from above>' DATABASE "zetl" SET HISTORY_MODE = TRUE;

Historical past mode turned on on the time of goal database creation on Amazon Redshift will allow historical past mode for current and new tables created sooner or later.

3. Run the next question to validate the profitable replication of the preliminary knowledge from the supply into Amazon Redshift:

choose is_history_mode, table_name, table_state, * from svv_integration_table_state;

The desk buyer ought to present table_state as Synced with is_history_mode as true.

Allow historical past mode for current zero-ETL integrations

Historical past mode might be enabled on your current zero-ETL integrations utilizing both the Amazon Redshift console or SQL instructions. Primarily based in your use case, you may activate historical past mode on the database, schema, or desk stage. To make use of the Amazon Redshift console, full the next steps:

1. On the Amazon Redshift console, select Zero-ETL integrations within the navigation pane.
2. Select your required integration.
3. Select Handle historical past mode.
   

On this web page, you may both allow or disable historical past mode for all tables or a subset of tables.

4. Choose Handle historical past mode for particular person tables and choose Activate for the historical past mode for the buyer
5. Select Save modifications.
   
6. To verify modifications, select Desk statistics and ensure Historical past mode is On for the buyer.
   
7. Optionally, you may run the next SQL command in Amazon Redshift to allow historical past mode for the buyer desk:

ALTER DATABASE "postgres" INTEGRATION SET HISTORY_MODE = TRUE FOR TABLE public.buyer;

8. Optionally, you may allow historical past mode for all present and tables created sooner or later within the database:

ALTER DATABASE "postgres" INTEGRATION SET HISTORY_MODE = TRUE FOR ALL TABLES;

9. Optionally, you may allow historical past mode for all present and tables created sooner or later in a number of schemas. The next question permits historical past mode for all present and tables created sooner or later for the public schema:

ALTER DATABASE "postgres" INTEGRATION SET HISTORY_MODE = TRUE FOR ALL TABLES IN SCHEMA public;

10. Run the next question to validate if the buyer desk has been efficiently modified to historical past mode with the is_history_mode column as true in order that it might probably start monitoring each model (together with updates and deletes) of all data modified within the supply:

choose is_history_mode, table_name, table_state, * from svv_integration_table_state;

Initially, the desk might be in ResyncInitiated state earlier than altering to Synced.

11. Run the next question within the zetl database of Aurora PostgreSQL-Suitable to switch a supply file and observe the conduct of historical past mode within the Amazon Redshift goal:

UPDATE buyer
SET
    ca_suite_number="Suite 100",
    ca_street_number="500",
    ca_street_name="Predominant",
    ca_street_type="St.",
    ca_city = 'New York',
    ca_county = 'Manhattan',
    ca_state="NY",
    ca_zip = '10001'
WHERE c_customer_id = 'AAAAAAAAAAAKNAAA';

12. Now run the next question within the postgres database of Amazon Redshift to see all variations of the identical file:

SELECT   
    c_customer_id,
    ca_street_number,
    ca_street_name,
    ca_suite_number,
    ca_city,
    ca_county,
    ca_state,
    ca_zip,
    _record_is_active,
    _record_create_time,
    _record_delete_time
FROM postgres.public.buyer
WHERE c_customer_id = 'AAAAAAAAAAAKNAAA';

Zero-ETL integrations with historical past mode has inactivated the outdated file with the _record_is_active column worth to false and created a brand new file with _record_is_active as true. You may also see the way it maintains the _record_create_time and _record_delete_time column values for each data. The inactive file has a delete timestamp that matches the energetic file’s create timestamp.

Load incremental knowledge in an SCD2 desk

Full the next steps to create an SCD2 desk and implement an incremental knowledge load course of in an everyday database of Amazon Redshift, on this case dev:

1. Create an empty buyer SDC2 desk known as customer_dim with SCD fields. The desk additionally has DISTSTYLE AUTO and SORTKEY columns _record_is_active, _record_create_time, and _record_delete_time. Whenever you outline a form key on a desk, Amazon Redshift can skip studying whole blocks of knowledge for that column. It may achieve this as a result of it tracks the minimal and most column values saved on every block and may skip blocks that don’t apply to the predicate vary.

CREATE TABLE dev.public.customer_dim (
    c_customer_sk bigint NOT NULL DEFAULT 0 ENCODE uncooked distkey,
    c_customer_id character various(19) DEFAULT '' :: character various ENCODE lzo,
    c_salutation character various(12) ENCODE bytedict,
    c_first_name character various(24) ENCODE lzo,
    c_last_name character various(36) ENCODE lzo,
    c_preferred_cust_flag character various(1) ENCODE lzo,
    c_birth_day integer ENCODE az64,
    c_birth_month integer ENCODE az64,
    c_birth_year integer ENCODE az64,
    c_birth_country character various(24) ENCODE bytedict,
    c_login character various(15) ENCODE lzo,
    c_email_address character various(60) ENCODE lzo,
    ca_street_number character various(12) ENCODE lzo,
    ca_street_name character various(72) ENCODE lzo,
    ca_street_type character various(18) ENCODE bytedict,
    ca_suite_number character various(12) ENCODE bytedict,
    ca_city character various(72) ENCODE lzo,
    ca_county character various(36) ENCODE lzo,
    ca_state character various(2) ENCODE lzo,
    ca_zip character various(12) ENCODE lzo,
    ca_country character various(24) ENCODE lzo,
    ca_gmt_offset numeric(5, 2) ENCODE az64,
    ca_location_type character various(24) ENCODE bytedict,
    _record_is_active boolean ENCODE uncooked,
    _record_create_time timestamp with out time zone ENCODE az64,
    _record_delete_time timestamp with out time zone ENCODE az64,
    PRIMARY KEY (c_customer_sk)
) SORTKEY (
    _record_is_active,
    _record_create_time,
    _record_delete_time
);

Subsequent, you create a saved process known as SP_Customer_Type2_SCD() to populate incremental knowledge within the customer_dim SCD2 desk created within the previous step. The saved process incorporates the next elements:

• • First, it fetches the max _record_create_time and max _record_delete_time for every customer_id.
  • Then, it compares the output of the previous step with the continued zero-ETL integration replicated desk for data created after the max creation time within the dimension desk or the file within the replicated desk with _record_delete_time after the max _record_delete_time within the dimension desk for every customer_id.
  • The output of the previous step captures the modified knowledge between the replicated buyer desk and goal customer_dim dimension desk. The interim knowledge is staged to a customer_stg desk, which is able to be merged with the goal desk.
  • Through the merge course of, data that should be deleted are marked with _record_delete_time and _record_is_active is ready to false, whereas newly created data are inserted into the goal desk customer_dim with _record_is_active as true.

2. Create the saved process with the next code:

CREATE OR REPLACE PROCEDURE public.sp_customer_type2_scd()
LANGUAGE plpgsql
AS $$
    BEGIN

    DROP TABLE IF EXISTS cust_latest;

    -- Create temp desk with newest file timestamps
         CREATE TEMP TABLE cust_latest DISTKEY (c_customer_id) 
    AS
        SELECT
            c_customer_id,
            max(_record_create_time) AS _record_create_time,
            max(_record_delete_time) AS _record_delete_time
        FROM customer_dim 
        GROUP BY c_customer_id;
    
    DROP TABLE IF EXISTS customer_stg;

    -- Determine and stage modified data
    CREATE TEMP TABLE customer_stg 
    AS           
    SELECT
            ABS(fnv_hash(cust.c_customer_id)) as customer_sk,
            cust.*
            FROM
                postgres.public.buyer cust
LEFT OUTER JOIN cust_latest ON cust.c_customer_id = cust_latest.c_customer_id
WHERE (cust._record_create_time > NVL(cust_latest._record_create_time, '1099-01-01 01:01:01') AND cust._record_is_active is true)
OR (cust._record_delete_time > NVL(cust_latest._record_delete_time, '1099-01-01 01:01:01') AND cust._record_is_active is fake);

    -- Merge modifications to buyer dimension desk
    MERGE INTO public.customer_dim 
    USING customer_stg stg 
    ON customer_dim.c_customer_id = stg.c_customer_id
        AND customer_dim._record_is_active = TRUE
        AND stg._record_is_active = false
    WHEN MATCHED THEN
        UPDATE
        SET
            _record_is_active = stg._record_is_active,
            _record_create_time = stg._record_create_time,
            _record_delete_time = stg._record_delete_time
    WHEN NOT MATCHED THEN
        INSERT
        VALUES
            (
                stg.customer_sk,
                stg.c_customer_id,
                stg.c_salutation,
                stg.c_first_name,
                stg.c_last_name,
                stg.c_preferred_cust_flag,
                stg.c_birth_day,
                 	     stg.c_birth_month,
                stg.c_birth_year,
                stg.c_birth_country,
                stg.c_login,
                stg.c_email_address,
                stg.ca_street_number,
                stg.ca_street_name,
                stg.ca_street_type,
                stg.ca_suite_number,
                stg.ca_city,
                stg.ca_county,
                stg.ca_state,
                stg.ca_zip,
                stg.ca_country,
                stg.ca_gmt_offset,
                stg.ca_location_type,
                stg._record_is_active,
                stg._record_create_time,
                stg._record_delete_time
            );

    END;
    $$

3. Run and schedule the saved process to load the preliminary and ongoing incremental knowledge into the customer_dim SCD2 desk:

CALL SP_Customer_Type2_SCD();

4. Validate the information within the customer_dim desk for a similar buyer with a modified handle:

SELECT
    c_customer_id,
    ca_street_number,
    ca_street_name,
    ca_suite_number,
    ca_city,
    ca_county,
    ca_state,
    ca_zip,
    _record_is_active,
    _record_create_time,
    _record_delete_time
FROM customer_dim
WHERE c_customer_id = 'AAAAAAAAAAAKNAAA';

You’ve efficiently applied an incremental load technique for the client SCD2 desk. Going ahead, all modifications to buyer might be tracked and maintained on this buyer dimension desk by operating the saved process. This lets you analyze buyer knowledge at a desired cut-off date for various use circumstances, for instance, performing buyer migration evaluation and seeing how geographical strikes influence buying conduct, or advertising and marketing marketing campaign effectiveness to research the influence of focused advertising and marketing campaigns on buyer demographics on the time of marketing campaign execution.

Trade use circumstances for historical past mode

The next are different business use circumstances enabled by historical past mode between operational knowledge shops and Amazon Redshift:

• Monetary auditing or regulatory compliance – Monitor modifications in monetary data over time to assist compliance and audit necessities. Historical past mode permits auditors to reconstruct the state of economic knowledge at any cut-off date, which is essential for investigations and regulatory reporting.
• Buyer journey evaluation – Perceive how buyer knowledge evolves to realize insights into conduct patterns and preferences. Entrepreneurs can analyze how buyer profiles change over time, informing personalization methods and lifelong worth calculations.
• Provide chain optimization – Analyze historic stock and order knowledge to determine traits and optimize inventory ranges. Provide chain managers can assessment how demand patterns have shifted over time, enhancing forecasting accuracy.
• HR analytics – Monitor worker knowledge modifications over time for higher workforce planning and efficiency evaluation. HR professionals can analyze profession development, wage modifications, and ability growth traits throughout the group.
• Machine studying mannequin auditing – Knowledge scientists can use historic knowledge to coach fashions, evaluate predictions vs. actuals to enhance accuracy, and assist clarify mannequin conduct and determine potential biases over time.
• Hospitality and airline business use circumstances – For instance:
  • Customer support – Entry historic reservation knowledge to swiftly handle buyer queries, enhancing service high quality and buyer satisfaction.
  • Crew scheduling – Monitor crew schedule modifications to assist adjust to union contracts, sustaining constructive labor relations and optimizing workforce administration.
  • Knowledge science functions – Use historic knowledge to coach fashions on a number of eventualities from totally different time durations. Evaluate predictions towards actuals to enhance mannequin accuracy for key operations corresponding to airport gate administration, flight prioritization, and crew scheduling optimization.

Greatest practices

In case your requirement is to separate energetic and inactive data, you should utilize _record_is_active as the primary kind key. For different patterns the place you need to analyze knowledge as of a particular date previously, no matter whether or not knowledge is energetic or inactive, _record_create_time and _record_delete_time might be added as kind keys.

Historical past mode retains file variations, which is able to enhance the desk measurement in Amazon Redshift and will influence question efficiency. Due to this fact, periodically carry out DML deletes for outdated file variations (delete knowledge past a sure timeframe if not wanted for evaluation). When executing these deletions, keep knowledge integrity by deleting throughout all associated tables. Vacuuming additionally turns into mandatory once you carry out DML deletes on data whose versioning is not required. To enhance auto vacuum delete effectivity, Amazon Redshift auto vacuum delete is extra environment friendly when working on bulk deletes. You’ll be able to monitor vacuum development utilizing the SYS_VACUUM_HISTORY desk.

Clear up

Full the next steps to wash up your assets:

1. Delete the Aurora PostgreSQL cluster.
2. Delete the Redshift cluster.
3. Delete the EC2 occasion.

Conclusion

Zero-ETL integrations have already made vital strides in simplifying knowledge integration and enabling close to real-time analytics. With the addition of historical past mode, AWS continues to innovate, offering you with much more highly effective instruments to derive worth out of your knowledge.

As companies more and more depend on data-driven decision-making, zero-ETL with historical past mode might be essential in sustaining a aggressive edge within the digital economic system. These developments not solely streamline knowledge processes but in addition open up new avenues for evaluation and perception technology.

To study extra about zero-ETL integration with historical past mode, discuss with Zero-ETL integrations and Limitations. Get began with zero-ETL on AWS by making a free account immediately!

Concerning the Authors

Raks Khare is a Senior Analytics Specialist Options Architect at AWS based mostly out of Pennsylvania. He helps clients throughout various industries and areas architect knowledge analytics options at scale on the AWS platform. Exterior of labor, he likes exploring new journey and meals locations and spending high quality time along with his household.

Jyoti Aggarwal is a Product Administration Lead for AWS zero-ETL. She leads the product and enterprise technique, together with driving initiatives round efficiency, buyer expertise, and safety. She brings alongside an experience in cloud compute, knowledge pipelines, analytics, synthetic intelligence (AI), and knowledge providers together with databases, knowledge warehouses and knowledge lakes.

Gopal Paliwal is a Principal Engineer for Amazon Redshift, main the software program growth of ZeroETL initiatives for Amazon Redshift.

Harman Nagra is a Principal Options Architect at AWS, based mostly in San Francisco. He works with international monetary providers organizations to design, develop, and optimize their workloads on AWS.

Sumanth Punyamurthula is a Senior Knowledge and Analytics Architect at Amazon Internet Providers with greater than 20 years of expertise in main giant analytical initiatives, together with analytics, knowledge warehouse, knowledge lakes, knowledge governance, safety, and cloud infrastructure throughout journey, hospitality, monetary, and healthcare industries.