fq/format/postgres/testdata/how_to.md

How to generate PostgreSQL test data

1) install postgres

Use this links to add repository and install PostgreSQL:

• https://www.postgresql.org/download/linux/
• https://www.postgresql.org/download/linux/redhat/
• https://www.postgresql.org/download/linux/debian/

You may install PostgreSQL with OS repository. But it may contains not all versions of PostgreSQL.

2) use default intallation location of postgres.

If you don't want default location. You may remove cluster and init it again.

# Detect PGDATA location:

ps aux | grep postgre

postgres     887  0.0  0.0 4334456 13608 ?       Ss   07:48   0:00 /usr/pgsql-14/bin/postmaster -D /u02/data

Result is:

• /u02/data - is PGDATA location
• /usr/pgsql-14/bin - location of PostgreSQL bin

3) init tables

# use postgres user

sudo su postgres

# then init pgbench tables

/usr/pgsql-14/bin/pgbench -i

# run simple test

/usr/pgsql-14/bin/pgbench -T 60 -j 100

4) run commands in psql

# start psql

/usr/pgsql-14/bin/psql

# display tables

\dt+

Schema |       Name       | Type  |  Owner   | Persistence | Access method |  Size  | Description
--------+------------------+-------+----------+-------------+---------------+--------+-------------
public | pgbench_accounts | table | postgres | permanent   | heap          | 13 MB  |
public | pgbench_branches | table | postgres | permanent   | heap          | 40 kB  |
public | pgbench_history  | table | postgres | permanent   | heap          | 968 kB |
public | pgbench_tellers  | table | postgres | permanent   | heap          | 40 kB  |

# run CHECKPOINT to avoid partially written data

CHECKPOINT;

# detect location of tables

SELECT pg_relation_filepath('pgbench_history');
pg_relation_filepath
----------------------
base/13746/24599

base/13746/24599 - location of table in PGDATA

5) use root account to copy table file

# login in root

sudo su

# go to PGDATA

cd /u02/data

# copy table file

cp base/13746/24599 /home/user

# change persmissions

chwon user:user /home/user/24599
chmod 644 /home/user/24599

6) Copy tables files to local with scp

scp user@192.168.0.100:~/24599 .

7) You may want to cut 2 pages (8192 * 2) from table

head -c 16384 ./245991 > ./24599_2pages

8) Locate pg_control file

global/pg_control inside PGDATA

9) Locate btree index

Get info about index:

\d pgbench_accounts
              Table "public.pgbench_accounts"
  Column  |     Type      | Collation | Nullable | Default 
----------+---------------+-----------+----------+---------
 aid      | integer       |           | not null | 
 bid      | integer       |           |          | 
 abalance | integer       |           |          | 
 filler   | character(84) |           |          | 
Indexes:
    "pgbench_accounts_pkey" PRIMARY KEY, btree (aid)

Then get path of pgbench_accounts_pkey:

select pg_relation_filepath('pgbench_accounts_pkey');
 pg_relation_filepath 
----------------------
 base/13746/24596

base/13746/24596 - is a path inside PGDATA of btree index pgbench_accounts_pkey.