database trending

Database Trending

Timothy J Bruce

For PDXPug 19

Jan 2012

Why the big deal?

New job No metrics Use performance tools

What type of Trending

What is management interested in?

What am I (the DBA) interested in?

Where to these things intersect?

What type of Trending

Not Current System / Database Performance

Historical System Information

Performance Tools

Ganglia

Hyperic

Monit

Munin

OpenNMS

Nagios

Zabbix

Zenoss

What's Important

How big is my database?

How big is my database growing?

pg_stat_database

One row per database, showing database OID, database name, number of active server processes connected to that database, number of transactions committed and rolled back in that database, total disk blocks read, and total buffer hits (i.e., block read requests avoided by finding the block already in buffer cache).

So I can get the OID. And use the pg_database_size (OID) function....

Database Size

So I can use this SQL command to get the size:

SELECT datname, cast(sum(pg_database_size(datid))/1024 as bigint ) FROM pg_stat_database GROUP BY datname;'

Size Process

Create two views One for ”today's size” One for ”Yesterday's size”

Why? I'm interested in what it looked like yesterday compared to today....

And if they're views, I can ”subtract” yesterday from today and display the total (difference).

Today's Database Size

Column | Type | Modifiers

---------------+--------+-----------

server_name | name |

database_name | name |

database_size | bigint |

View definition:

SELECT database_size_stats.server_name, database_size_stats.database_name, database_size_stats.database_size

FROM database_size_stats

WHERE database_size_stats.date_collected >= now()::date

ORDER BY database_size_stats.database_name;

Database Sizing....

My database is growing by around 6 Gb a day.

Really?

What's causing it to grow?

Table Size

So what's my biggest table?

And how do I find out which one?

pg_stat_user_tables

For each table in the current database (including TOAST tables), the table OID, schema and table name, number of sequential scans initiated, number of live rows fetched by sequential scans, number of index scans initiated (over all indexes belonging to the table), number of live rows fetched by index scans, numbers of row insertions, updates, and deletions, the last time the table was vacuumed manually, the last time it was vacuumed by the autovacuum daemon, the last time it was analyzed manually, and the last time it was analyzed by the autovacuum daemon.

Table Size


insert into table_stats ( reloid, schemaname, relname, rec_ins, rec_del, rec_upd )

select u.relid, u.schemaname, u.relname, u.n_tup_ins, u.n_tup_del, u.n_tup_upd, from pg_stat_user_tables u;

Table Size Process

Again - Create two views One for ”today's size” One for ”Yesterday's size”

Why? Frequently I'm looking at today's size AND I'm interested in what it looked like yesterday compared to today....

And since they're views, I can ”subtract” yesterday from today and display the total (difference) and email it out.

Table Size Process Side-Effect

I can collect the number of records read as well.

number of sequential scans initiated number of live rows fetched by sequential

scans number of index scans initiated (over all

indexes belonging to the table) number of live rows fetched by index scans

Record Count

select reltuples from pg_class

Real Table Data


insert into table_stats ( reloid, schemaname, relname, last_vacuum, last_autovacuum, last_analyze, last_autoanalyze, rec_ins, rec_del, rec_upd, rec_seq_scan, rec_seq_read, rec_idx_scan, rec_idx_read, rec_total )

select u.relid, u.schemaname, u.relname, u.last_vacuum, u.last_autovacuum, u.last_analyze, u.last_autoanalyze, u.n_tup_ins, u.n_tup_del, u.n_tup_upd, u.seq_scan, u.seq_tup_read, u.idx_scan, u.idx_tup_fetch, ( select reltuples from pg_class c where c.relname = u.relname and c.relnamespace = ( SELECT n.oid FROM pg_namespace n WHERE n.nspname = u.schemaname ) ) as "recs" from pg_stat_user_tables u;

Schedule the Jobs

An account that has access to read all the information (public schema) and insert the data into my private schema.

Job is scheduled for early in the morning – just after midnight.

A view called ”Today” looks at the data as of today's morning run (yesterday's data).

A view called ”Yesterday” looks at the data from yesterday's morning run (the day before's data).

Table AnalysisCMD="SELECT * FROM dba.v_table_info_change "

function SQL {

COLUMN=$1

CMD1="$CMD "

CMD2=" WHERE $COLUMN IS NOT NULL ORDER BY $COLUMN DESC LIMIT 10; "

SQLCMD="$CMD1 $CMD2"

echo "$SQLCMD" >> $TMP_LOG_FILE

$PSQL -c "$SQLCMD" pfprod >> $RESULTS 2>&1

If [ "$?” != "0" ]; then

echo "Table Stats Analysis failed for $COLUMN " >> $TMP_LOG_FILE

fi

}

Table Analysis cont'decho `/usr/ucb/hostname` " :: Table Stats started at `date`" >>

$TMP_LOG_FILE

date > $RESULTS

SQL ins

SQL del

SQL upd

SQL seq_read

SQL idx_read

SQL total

echo "Database Size Analysis completed at `date`" >> $TMP_LOG_FILE

mailx -s "Table Stats Analysis" $MAIL_USERS < $RESULTS

Next Steps

pg_bloat? (But there are issues with pg_bloat)

index sizes and growth?

References

PostgreSQL Documentation - http://www.postgresql.org/docs/current/static/monitoring-stats.html#MONITORING-STATS-VIEWS

Reference Email: From: Ondrej Ivanič Date: Wed, December 28, 2011 17:38 To: [email protected]

Questions

Your Turn....

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