How to dynamically pass psql variable value at runtime? - postgresql

Question

I am trying to create shortcuts for DBAs/admins in psql.
I have created some functions and queries, which give me information such as schema size in bytes, or a list of tables in order of storage used, etc. These will be used whenever an admin or DBA wants to get some info about the database.
I can run these queries naturally with select, or as a function like get_size(), but I want them to be accessible as shortcuts, similar to the native backslash commands (\dx, \dt, etc).
So I have used psql's \set feature to store queries/functions as variables, which I will put in the psqlrc file:
\set size 'select pg_size_pretty(my_size_function(''public''));'
Then when I type :size in psql I would get the size of the "public" schema.
What I want though, is to be able to dynamically pass a schema name, so I could run things like
:size public, :size schema2 etc.
I tried changing the \set to: \set size 'select pg_size_pretty(my_size_function(:schema));', but I can only call that by executing \set schema '''public''' first.
Since the whole point is to use these universally as shortcuts, having to manually run \set commands each time defeats the purpose.
In Oracle the would be colon a bind variable, which would be read at runtime.
How can I do this with psql?

Answer 1

I use these ways.
Postgres Functions (Inside Postgres CLI)
postgres=# CREATE OR REPLACE FUNCTION getSize(tableName varchar) RETURNS varchar LANGUAGE SQL as
postgres-# $$
postgres$# SELECT pg_size_pretty(pg_relation_size(tableName));
postgres$# $$;
CREATE FUNCTION
postgres=# select getSize('test');
getsize
------------
8192 bytes
(1 row)
From Shell (Outside Postgres CLI)
psqlgettablesize(schema, tablename) - Get table size. Pass all for schema argument to get for all schemas.
$ psqlgettablesize customer events
table_name | total_size | table_size | index_size
--------------------------+---------------------+-------------+---------------
test(complete database) | 19039892127 (18 GB) | |
--------- | --------- | --------- | ---------
customer.events | 24576 (24 kB) | 0 (0 bytes) | 24576 (24 kB)
(3 rows)
psqlgettablecount(schema, tablename) - Get count of rows in a table, in a schema
$ psqlgettablecount customer events
count
----------
51850000
(1 row)
psqlgetvacuumdetails(schema, tablename) - Get vacuum details of a table, in a schema
$ psqlgetvacuumdetails customer events
schemaname | relname | n_live_tup | n_dead_tup | last_analyze | analyze_count | last_autoanalyze | autoanalyze_count | last_vacuum | vacuum_count | last_autovacuum | autovacuum_count
------------+-----------+------------+------------+----------------------------+---------------+----------------------------+-------------------+---------------------------+--------------+-----------------+------------------
customer | events | 0 | 0 | 2019-12-02 18:25:04.887653 | 2 | 2019-11-27 18:49:19.002405 | 1 | 2019-11-29 13:11:15.92002 | 1 | | 0
(1 row)
psqltruncatetable(schema, tablename) - Truncate a table, in a schema, after authorization.
$ psqltruncatetable customer events
Are you sure to truncate table 'customer.events' (y/n)? y
Time: 4.944 ms
psqlsettings(category) - Get settings of Postgres
$ psqlsettings Autovacuum
name | setting | unit | category | short_desc | extra_desc | context | vartype | source | min_val | max_val | enumvals | boot_val | reset_val | sourcefile | sourceline | pending_restart
-------------------------------------+-----------+------+------------+-------------------------------------------------------------------------------------------+------------+------------+---------+---------+---------+------------+----------+-----------+-----------+------------+------------+-----------------
autovacuum | on | | Autovacuum | Starts the autovacuum subprocess. | | sighup | bool | default | | | | on | on | | | f
autovacuum_analyze_scale_factor | 0.1 | | Autovacuum | Number of tuple inserts, updates, or deletes prior to analyze as a fraction of reltuples. | | sighup | real | default | 0 | 100 | | 0.1 | 0.1 | | | f
psqlselectrows(schema, tablename) - Get rows from a table, in a schema
$ psqlselectrows customer events
id | name
----+------
1 | Clicked
2 | Page Loaded
(10 rows)
#Colors
B_BLACK='\033[1;30m'
B_RED='\033[1;31m'
B_GREEN='\033[1;32m'
B_YELLOW='\033[1;33m'
B_BLUE='\033[1;34m'
B_PURPLE='\033[1;35m'
B_CYAN='\033[1;36m'
B_WHITE='\033[1;37m'
RESET='\033[0m'
#Postgres Command With Params
psqlcommand="$POSTGRES_BIN/psql -U postgres test -q -c"
function psqlgettablesize()
{
[ -z "$1" ] && echo -e "${B_RED}Argument 1 missing. Schema name needed. ${B_YELLOW}(Pass 'all' to get details from all schema(s)${RESET}" ||
{
criteria="and table_schema = '$1'"
if [ "$1" == "all" ]; then
criteria=""
fi
if [ "$2" != "" ]; then
criteria+=" and table_name = '$2'"
fi
[ -z "$2" ] && echo -e "${B_YELLOW}Table name not given. ${B_GREEN}Showing size of all tables in $1 schema(s)${RESET}"
query="SELECT
concat(current_database(), '(complete database)') AS table_name, concat(pg_database_size(current_database()), ' (', pg_size_pretty(pg_database_size(current_database())), ')') AS total_size, '' AS table_size, '' AS index_size
UNION ALL SELECT '---------','---------','---------','---------'
UNION ALL SELECT
table_name,
concat(total_table_size, ' (', pg_size_pretty(total_table_size), ')'),
concat(table_size, ' (', pg_size_pretty(table_size), ')'),
concat(index_size, ' (', pg_size_pretty(index_size), ')')
FROM (
SELECT
concat(table_schema, '.', table_name) AS table_name,
pg_total_relation_size(concat(table_schema, '.', table_name)) AS total_table_size,
pg_relation_size(concat(table_schema, '.', table_name)) AS table_size,
pg_indexes_size(concat(table_schema, '.', table_name)) AS index_size
FROM information_schema.tables where table_schema !~ '^pg_' AND table_schema <> 'information_schema' $criteria ORDER BY total_table_size) AS sizes";
$psqlcommand "$query"
}
}
function psqlgettablecount()
{
[ -z "$1" ] && echo -e "${B_RED}Argument 1 missing: Need schema name${RESET}"
[ -z "$2" ] && echo -e "${B_RED}Argument 2 missing: Need table name${RESET}" ||
$psqlcommand "select count(*) from $1.$2;"
}
function psqlgetvacuumdetails()
{
[ -z "$1" ] && echo -e "${B_RED}Argument 1 missing: Need schema name${RESET}" ||
[ -z "$2" ] && echo -e "${B_RED}Argument 2 missing: Need table name${RESET}" ||
$psqlcommand "SELECT schemaname, relname, n_live_tup, n_dead_tup, last_analyze::timestamp, analyze_count, last_autoanalyze::timestamp, autoanalyze_count, last_vacuum::timestamp, vacuum_count, last_autovacuum::timestamp, autovacuum_count FROM pg_stat_user_tables where schemaname = '$1' and relname='$2';"
}
function psqltruncatetable()
{
[ -z "$1" ] && echo -e "${B_RED}Argument 1 missing: Need schema name${RESET}" ||
[ -z "$2" ] && echo -e "${B_RED}Argument 2 missing: Need table name${RESET}" ||
{
read -p "$(echo -e ${B_YELLOW}"Are you sure to truncate table '$1.$2' (y/n)? "${RESET})" choice
case "$choice" in
y|Y ) $psqlcommand "TRUNCATE $1.$2;";;
n|N ) echo -e "${B_GREEN}Table '$1.$2' not truncated${RESET}";;
* ) echo -e "${B_RED}Invalid option${RESET}";;
esac
}
}
function psqlsettings()
{
query="select * from pg_settings"
if [ "$1" != "" ]; then
query="$query where category like '%$1%'"
fi
query="$query ;"
$psqlcommand "$query"
if [ -z "$1" ]; then
echo -e "${B_YELLOW}Passing Category as first argument will filter the related settings.${RESET}"
fi
}
function psqlselectrows()
{
[ -z "$1" ] && echo -e "${B_RED}Argument 1 missing: Need schema name${RESET}" ||
[ -z "$2" ] && echo -e "${B_RED}Argument 2 missing: Need table name${RESET}" ||
$psqlcommand "SELECT * from $1.$2"
}

Answer 2

I couldn't figure out how to dynamically pass variables so I settled for a system of aliases and variables that work together to provide what I was looking for. So I can run :load_schema <schemaname> and then run commands interacting with the "loaded" schema. Loading a schema is simply aliasing a \set command. This way people who are unfamiliar with psql can just press : and tab autocomplete will show them all of my shortcuts.
All my code is here.
This isn't exactly what I was looking for so I won't accept it but it's close enough to post in case anyone else wants to do this.