Encrypted Connection (TLS)

• The communication between the SQL Server instance and the client application is encrypted while data travels across the network.​
• The traffic is encrypted using TLS (Transport Layer Security) before it leaves the client and decrypted only by SQL Server.
• The encrypted tunnel protects:​
• Login credentials
• SQL statements and Stored Procedure calls​
• Query results

Create a Self-Signed Certificate in the SQL Server​​ 

Locate the Certificate​

Grant SQL Server Access to Certificate’s Private Key​

 

Export Certificate for Clients​

Configure SQL Server to Use the Certificate​

Import the exported certificate​ into the client application server​

Verification

An expired TLS cert can cause client connections to fail.​

For replacing the TLS certificate, you can execute the same PowerShell command to create a new certificate and then configure the SQL Server to apply the new certificate, as shown in the steps above.​

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object_id - ALTER PROC vs DROP and CREATE PROC

Using ALTER PROC to deploy changes preserves the object_id. Using DROP followed by CREATE changes the object_id. This is important for DBAs managing Forced Plans. When object_id changes, Query Store generates a new sys.query_store_query entry with a new query_id, even if the query text remains the same. The forced plan stops working in this case, and DBAs must reconfigure it. 

Testing:

CREATE PROC TestSP
AS
BEGIN
SELECT 1;
END;
GO
SELECT * FROM sys.objects WHERE name ='TestSP';
GO
ALTER PROC TestSP
AS
BEGIN
SELECT 2;
END;
GO
SELECT * FROM sys.objects WHERE name ='TestSP';
GO
DROP PROC TestSP;
GO
CREATE PROC TestSP
AS
BEGIN
SELECT 2;
END;
GO
SELECT * FROM sys.objects WHERE name ='TestSP';

Access Oracle database data from SQL Server using PolyBase

USE master;

GO

-- Verify PolyBase is Installed

SELECT SERVERPROPERTY('IsPolyBaseInstalled') AS IsPolyBaseInstalled;

GO

-- Check PolyBase configuration

EXEC sp_configure 'polybase enabled';

GO

/* -- if needed:

EXEC sp_configure 'show advanced options',1;

RECONFIGURE;

GO

EXEC sp_configure 'polybase enabled',1;

RECONFIGURE;

GO

*/

USE test_db; /* USER DATABASE */

GO

-- Check whether a Database Master Key exists

SELECT *

FROM sys.symmetric_keys

WHERE name = '##MS_DatabaseMasterKey##';

GO

-- List all database scoped credentials

SELECT

    credential_id,

    name,

    credential_identity,

    create_date,

    modify_date

FROM sys.database_scoped_credentials

ORDER BY name;

GO

-- Create Database Master Key in User Database if needed

USE test_db;

GO

CREATE MASTER KEY ENCRYPTION BY PASSWORD = '<$345>FeQ2@S3PEm+87B';

GO

-- Verify

SELECT * FROM sys.symmetric_keys WHERE name = '##MS_DatabaseMasterKey##';

GO

-- Create Database Scoped Credential

CREATE DATABASE SCOPED CREDENTIAL OracleCred WITH IDENTITY = 'POLYBASE_READ', SECRET = '<$345>FeQ2@S3PEm+87B';

GO

-- Verify

SELECT * FROM sys.database_scoped_credentials;

GO

-- Create External Data Source

CREATE EXTERNAL DATA SOURCE OracleDS WITH (

    LOCATION = 'oracle://ORACLESERVER:1600',

    CONNECTION_OPTIONS = 'ServiceName=ORACLESERVER.domain.com',

    CREDENTIAL = OracleCred

);

GO

-- Verify

SELECT * FROM sys.external_data_sources;

GO

-- Create External Table

CREATE EXTERNAL TABLE MODELDB_GLOBAL_RMS_ISSUE

(

    RMS_ID      DECIMAL(38,0) NOT NULL,

    ISSUE_ID    CHAR(10) COLLATE Latin1_General_100_BIN2_UTF8 NOT NULL,

    FROM_DT     DATETIME2(0) NOT NULL,

    THRU_DT     DATETIME2(0) NOT NULL

)

WITH

(

    LOCATION = '[ORACLESERVER.domain.com].MODELDB_GLOBAL.RMS_ISSUE',

    DATA_SOURCE = OracleDS

);

GO

-- Verify (check Actual Execution Plan XML, see whether 'pushdown' occurred)

SELECT TOP 10 * FROM MODELDB_GLOBAL_RMS_ISSUE;

-- USAGE

select * into #modeldb_global__rms_issue from MODELDB_GLOBAL_RMS_ISSUE;

SELECT COUNT(1) FROM #modeldb_global__rms_issue;

SELECT TOP 10 * FROM #modeldb_global__rms_issue;

Azure PostgreSQL built-in Health Recovery

During my testing of CLUSTER and PG_REPACK on Azure PostgreSQL, I found that Azure PostgreSQL has an automatic health recovery mechanism. This feature drops running processes on the Postgres database when it detects an unhealthy server condition, such as full storage.

Enable Audit

SHOW shared_preload_libraries;

-- Azure Portal -> Server parameters -> shared_preload_libraries -> Add PGAUDIT

SELECT name

FROM pg_available_extensions

WHERE name = 'pgaudit';

SHOW azure.extensions;

-- Azure Portal -> Server parameters -> azure.extensions -> Add PGAUDIT

CREATE EXTENSION IF NOT EXISTS pgaudit;

SHOW pgaudit.log;

-- Azure Portal -> Server parameters -> pgaudit.log -> ALL

SHOW log_line_prefix;

-- Azure Portal -> Server parameters -> log_line_prefix -> %t-%c-user=%u,db=%d,app=%a,client=%h

CLUSTER

-- This command is metadata only; it set the default index for future CLUSTER operations. It does not actually re-cluster the table.

ALTER TABLE curves.xc_curve

CLUSTER ON xc_curve_pk;

-- verify the clustered index

SELECT

    c.relname AS table_name,

    i.relname AS index_name

FROM pg_class c

JOIN pg_index x

    ON c.oid = x.indrelid

JOIN pg_class i

    ON i.oid = x.indexrelid

WHERE x.indisclustered

  AND c.oid = 'curves.xc_curve'::regclass;

/*

 * This command is Session wide only (for the duration of that specific connection).

 * It will not apply to the whole server or all users.

 */

SET maintenance_work_mem = '8GB';

SHOW maintenance_work_mem;

\timing on

/*

 * For a 1.8 TB table, I would typically want at least 2–2.5 TB of free storage beyond the current database size before attempting a CLUSTER, otherwise there is a real risk of running out of space and having the operation fail.

 */

CLUSTER VERBOSE curves.xc_curve USING xc_curve_pk;

-- Check CLUSER running

SELECT

    pid,

    usename,

    application_name,

    state,

    wait_event_type,

    wait_event,

    now() - query_start AS runtime,

    query

FROM pg_stat_activity

WHERE query ILIKE 'CLUSTER%';

PG_REPACK

CREATE EXTENSION pg_repack;

 -- PGSQL pg_repack

pg_repack -t curves.xc_curve -d axioma -h us5-dp-d-pg1.postgres.database.azure.com -U breakglass -k

-- Check PG_REPACK running:
SELECT pid,

       usename,

       application_name,

       state,

       wait_event_type,

       wait_event,

       query

FROM pg_stat_activity

WHERE application_name LIKE '%repack%';

Health recovery

An internal Azure process executed the pg_terminate_backend command to kill the CLUSTER connection.

/*
 * SELECT pg_terminate_backend(pid) FROM pg_stat_activity WHERE backend_type = 'client backend' AND usename<> 'azuresu' AND usename<> 'replication' AND pg_catalog.pg_is_in_recovery() = false and (SELECT setting = 'on' FROM pg_settings WHERE name = 'default_transaction_read_only')

 */

 

Analyzing PostgreSQL Query Performance

To evaluate the performance of a PostgreSQL query, we can utilize the EXPLAIN command. In pgAdmin, upon opening a query window, you will find two buttons located on the top menu bar.

Core Comparison

	EXPLAIN	EXPLAIN ANALYZE
Execution	Does not run the query.	Executes the query completely.
Speed	Instantaneous (takes milliseconds).	Takes as long as the query itself to run.
Data Safety	100% safe for all commands.	Modifies data if used on INSERT/UPDATE/DELETE.
Metrics	Theoretical estimates (cost, rows, width).	Real runtime stats (actual time, actual rows, memory).

Because EXPLAIN ANALYZE actually runs the query, it is important to enclose the entire script with START TRANSACTION and ROLLBACK commands when analyzing DML statements. If you do not take this step, you might unintentionally modify the table data while analyzing the query. To avoid such unintended changes, always use these transaction commands during your analysis.

To analyze your query in the pgAdmin query window, select the START TRANSACTION, EXPLAIN ANALYZE, and the specific query, then hit F5 to run it, such as:

After that, you can highlight the complete output, copy it, and insert it into a text file.

Finally, you should highlight a ROLLBACK command, then execute it.

Be aware that executing the full set of commands (START TRANSACTION, EXPLAIN, your SQL query, ROLLBACK) together will lead to the ROLLBACK canceling the EXPLAIN output, which means you won't be able to access the information you need.

Additionally, you can retrieve the BUFFERS, COST, and TIMING data from the real execution plan by running EXPLAIN (ANALYZE, BUFFERS, TIMING, COSTS).

ANALYZE BUFFERS is the gold standard for query optimization because it reveals the exact I/O footprint of a query. While ANALYZE executes the query to show actual runtime and row counts, BUFFERS shows exactly how many data blocks (pages) Postgres had to read, write, Postgres handles data in blocks, where 1 block = 8 KiB by default.