Vacuum article

Author: ScaryDBA

11_VacuumIntro/vacuum.sql

@@ -0,0 +1,81 @@
+-- Just the basic VACUUM operation
+VACUUM;
+
+
+-- Equivalent to SHRINK
+VACUUM (FULL);
+
+
+-- Targeting a table
+VACUUM radio.antenna;
+
+-- Targeting more than one table
+VACUUM radio.antenna, radio.bands, radio.digitalmodes  
+
+
+
+-- Adding, then removing, dummy data to see this in action
+INSERT INTO radio.countries 
+(country_name)
+SELECT generate_series(1,15000,1);
+
+DELETE FROM radio.countries 
+WHERE country_id BETWEEN 3 AND 12000;
+
+VACUUM (VERBOSE) radio.countries;
+
+--cleanup and reset from above
+DELETE FROM radio.countries 
+WHERE country_id > 2;
+
+ALTER TABLE radio.countries ALTER COLUMN country_id RESTART WITH 3;
+
+
+SELECT * FROM radio.countries c;
+
+
+
+--ANALYZE
+VACUUM (ANALYZE);
+
+
+--Just ANALYZE
+ANALYZE;
+
+--ANALYZE and then look at STATISTICS
+VACUUM (ANALYZE) radio.countries;
+
+--ensure we have a clean set of statistics, then review them
+VACUUM (ANALYZE) radio.countries;
+
+SELECT
+	ps.histogram_bounds
+FROM
+	pg_stats AS ps
+WHERE
+	ps.tablename = 'countries';
+
+
+--modify the data and then look at STATISTICS 
+INSERT INTO radio.countries 
+(country_name)
+SELECT generate_series(1,15000,1);
+
+SELECT
+	ps.histogram_bounds
+FROM
+	pg_stats AS ps
+WHERE
+	ps.tablename = 'countries';
+
+VACUUM (ANALYZE) radio.countries;
+
+SELECT
+	ps.histogram_bounds
+FROM
+	pg_stats AS ps
+WHERE
+	ps.tablename = 'countries';
+
+--VERBOSE and ANALYZE 
+

SampleData.sql

@@ -7,7 +7,7 @@ VALUES
 INSERT INTO radio.countries
 (country_name)
 VALUES
-('USA'),('Great Britain');
+('USA'),('United Kingdom');
 
 INSERT INTO radio.bands
 (band_name,frequency_start_khz,frequency_end_khz,country_id)