以编程方式将设置保存到postgresql.conf

Question

I have lots of Postgres instances to manage. And it's very annoying and a huge waste of time when I have to change some postgresql.conf setting in all of them.

But Postgres 9.3 does not have a function to persist settings values directly to the postgresql.conf file (it was introduced in 9.4 )

Answer 1

So, I decided to make my own:

create or replace function f_save_postgresql_conf(pname text, pvalue text)
RETURNS text AS
$BODY$
DECLARE
  vTEXT         TEXT;
  vCONF_FILE_LOCATION   TEXT;
  vRECORD       RECORD;
  vCATEGORY     TEXT;
  vMAXLENGTH        INTEGER;
  vSETTING      TEXT;
  vSETTING_DEFAULT  TEXT;
BEGIN
    -- ===================================================================================
    -- The intent of this function is to fulfill the lack of ways of changing postgresql.conf
    -- "programatically" (using nothing but a "query" - not external or 3party tools).

    -- The way it does it is 
    --  - loading parameter values from original postgresql.conf (discards any comments)
    --  - rewriting a fresh new postgresql.conf with all parameters present in pg_settings

    -- Parameters:
    -- - pname    : the name of the setting to be changed (if empty, no setting will be changed)
    -- - pvalue   : the value of the setting to be changed

    -- Result:
    -- text : the new content of the file "postgresql.conf"

    -- ===================================================================================


    -- ===================================================================================
    -- gets the max length name parameters (just for padding)
    -- ===================================================================================
    SELECT  MAX(LENGTH(NAME))
    INTO    vMAXLENGTH
    FROM    PG_SETTINGS;


    -- ===================================================================================
    -- creates a temp table (temp_pg_settings) which will hold settings present in postgresql.conf 
    -- ===================================================================================
    create temporary table temp_pg_settings (name text primary key, setting text) on commit drop;


    -- ===================================================================================
    -- load postgresql.conf lines into a temp table (temp_postgresql_conf)
    -- ===================================================================================
    vCONF_FILE_LOCATION = ((select setting from pg_settings where name = 'data_directory') || '/postgresql.conf');
    create temporary table temp_postgresql_conf (line text) on commit drop;
    execute 'copy temp_postgresql_conf from ''' || vCONF_FILE_LOCATION || ''' delimiter ''º'' ';

    -- ===================================================================================
    -- searchs temp_postgresql_conf (postgresql.conf lines) to find uncommented settings
    -- ===================================================================================
    for vRECORD IN  (
            select  trim(substr(line, 1, strpos(line,'=')-1))           as name,
                    trim(substr(line,strpos(line,'=')+1, length(line))) as setting
                    from    (
                select  trim(replace(
                            case when strpos(line,'#') > 0 then substr(line,1, strpos(line,'#')-1)
                            else line 
                            end
                        ,'  ',' ')) as line 
                            from    temp_postgresql_conf
                ) a 
                    where   line not like '#%'
                    and line <> ''
                    order by 1
                    )
    loop
        -- raise notice '% = %', vRECORD.name, vrecord.setting;
        -- insert into temp_pg_settings the parameter and it's value (present in postgresql.conf)
        insert into temp_pg_settings (name, setting) values (vrecord.name, vrecord.setting);
    end loop;


    -- ===================================================================================
    -- if function's parameter "pname" is not empty, then sets the setting with new value
    -- ===================================================================================
    if (coalesce(pname,'') <> '') then
        if (select count(*) from pg_settings where name = pname) = 0 then
            raise exception 'Settings name = "%" does not exist!', pname;
        end if;
        delete from temp_pg_settings where name = pname;
        insert into temp_pg_settings (name, setting) values (pname,pvalue);
    end if;


    -- ===================================================================================
    -- creates another temp table just to generate the fresh new content of postgresql.conf
    -- ===================================================================================
    create temporary table temp_new_postgresql_conf (seq serial primary key, line text) on commit drop;


    -- ===================================================================================
    -- iterates over pg_settings settings, generating postgresql.conf content based on settings present in temp_pg_settings
    -- ===================================================================================
    vCATEGORY = '';
    for vRECORD in (select ps.*, tps.name as tname, tps.setting as tsetting 
            from pg_settings ps
            left join temp_pg_settings tps on ps.name = tps.name 
            order by ps.category, case when tps.name is not null then 0 else 1 end, ps.name
            )
    loop

            -- if category has changed since last record
            if (vCATEGORY <> vRECORD.category) then
                -- insert category name
                insert into temp_new_postgresql_conf (line) values 
                (''),
                ('#------------------------------------------------------------------------------------------------------------------------------------------------------------'),
                ('# ' || upper(vRECORD.category) ),
                ('#------------------------------------------------------------------------------------------------------------------------------------------------------------');
                vCATEGORY = vRECORD.category;
            end if;



            -- if parameters is commented in original postgresql.conf file, then insert it commented as well
            if (vRECORD.tname is null) then
                vTEXT = '#';
            -- otherwise, insert it uncommented
            else
                vTEXT = '';
            end if;

            -- gets the parameter name
            vTEXT = vTEXT || vRECORD.NAME;
            vTEXT = rpad(vTEXT, vMAXLENGTH) || '  =  ';

            -- gets the parameter value
            if (vRECORD.tname is null) then
                vSETTING = coalesce(vRECORD.boot_val,'');
            else
                vSETTING = coalesce(vRECORD.tsetting,'');
            end if;
            if (vRECORD.vartype = 'string' and strpos(vSETTING,'''') = 0) then
                vSETTING = '''' || vSETTING || '''';
            end if;
            vTEXT = vTEXT || vSETTING;


            -- appends extra information (comments)
            vTEXT = rpad(vTEXT,GREATEST(length(vTEXT),75)) || ' #';

            -- values range/types/etc...
            case    when coalesce(vRECORD.vartype,'') = 'bool' 
                then vTEXT = vTEXT || ' on/off';
                when vRECORD.enumvals is not null
                then vTEXT = vTEXT || ' ' || (vRECORD.enumvals::text);
                when coalesce(vRECORD.min_val,'') <> '' or coalesce(vRECORD.max_val,'') <> '' 
                then vTEXT = vTEXT || ' ' || coalesce(vRECORD.min_val,'') || ' to ' || coalesce(vRECORD.max_val,'') 
                                                  || (case when coalesce(vRECORD.unit,'') <> '' then ' (' || coalesce(vRECORD.unit,'') || ')' else '' end);
                else vTEXT = vTEXT;
            end case;

            -- default value (if different from current one)
            vSETTING_DEFAULT = coalesce(vRECORD.boot_val,'');
            if (vRECORD.vartype = 'string' and strpos(vSETTING_DEFAULT,'''') = 0) then
                vSETTING_DEFAULT = '''' || vSETTING_DEFAULT || '''';
            end if;
            if (vSETTING_DEFAULT <> vSETTING) then
                vTEXT = vTEXT || ' (default='|| vSETTING_DEFAULT || ')';

            end if;


            -- appends setting's description
            vTEXT = rpad(vTEXT,GREATEST(length(vTEXT),140)) || ' ' || coalesce(vRECORD.short_desc,'');      
            if coalesce(vRECORD.extra_desc,'') <> '' then
                vTEXT = vTEXT || coalesce(vRECORD.extra_desc,'');
            end if;

            -- insert the "line" into the table
            insert into temp_new_postgresql_conf (line) values (vTEXT);
    end loop;

    -- saves the new text over the old postgresql.conf
    execute 'copy (select line from temp_new_postgresql_conf) to ''' || vCONF_FILE_LOCATION || ''' delimiter ''º'' ';

    -- reload the postgresql.conf settings
    perform pg_reload_conf();

    -- mounts the postgresql.conf new text just to return it
    vTEXT = '';
    for vRECORD in (select * from temp_new_postgresql_conf order by seq)
    loop
        --raise notice '%', vRECORD.line;
        vTEXT = vTEXT || vRECORD.line || chr(13);
    end loop;
    return vTEXT;

end;
$BODY$
LANGUAGE plpgsql VOLATILE;

And this is how postgresql.conf looks like after changes:

#------------------------------------------------------------------------------------------------------------------------------------------------------------
# AUTOVACUUM
#------------------------------------------------------------------------------------------------------------------------------------------------------------
#autovacuum                          =  on                                  # on/off                                                         Starts the autovacuum subprocess.
#autovacuum_analyze_scale_factor     =  0.1                                 # 0 to 100                                                       Number of tuple inserts, updates, or deletes prior to analyze as a fraction of reltuples.
#autovacuum_analyze_threshold        =  50                                  # 0 to 2147483647                                                Minimum number of tuple inserts, updates, or deletes prior to analyze.
#autovacuum_freeze_max_age           =  200000000                           # 100000000 to 2000000000                                        Age at which to autovacuum a table to prevent transaction ID wraparound.
#autovacuum_max_workers              =  3                                   # 1 to 8388607                                                   Sets the maximum number of simultaneously running autovacuum worker processes.
#autovacuum_multixact_freeze_max_ag  =  400000000                           # 10000000 to 2000000000                                         Multixact age at which to autovacuum a table to prevent multixact wraparound.
#autovacuum_naptime                  =  60                                  # 1 to 2147483 (s)                                               Time to sleep between autovacuum runs.
#autovacuum_vacuum_cost_delay        =  20                                  # -1 to 100 (ms)                                                 Vacuum cost delay in milliseconds, for autovacuum.
#autovacuum_vacuum_cost_limit        =  -1                                  # -1 to 10000                                                    Vacuum cost amount available before napping, for autovacuum.
#autovacuum_vacuum_scale_factor      =  0.2                                 # 0 to 100                                                       Number of tuple updates or deletes prior to vacuum as a fraction of reltuples.
#autovacuum_vacuum_threshold         =  50                                  # 0 to 2147483647                                                Minimum number of tuple updates or deletes prior to vacuum.

#------------------------------------------------------------------------------------------------------------------------------------------------------------
# CLIENT CONNECTION DEFAULTS / LOCALE AND FORMATTING
#------------------------------------------------------------------------------------------------------------------------------------------------------------
default_text_search_config           =  'pg_catalog.english'                # (default='pg_catalog.simple')                                  Sets default text search configuration.
lc_messages                          =  'C'                                 # (default='')                                                   Sets the language in which messages are displayed.
lc_monetary                          =  'C'                                 #                                                                Sets the locale for formatting monetary amounts.
lc_numeric                           =  'C'                                 #                                                                Sets the locale for formatting numbers.
lc_time                              =  'C'                                 #                                                                Sets the locale for formatting date and time values.
#DateStyle                           =  'ISO, MDY'                          #                                                                Sets the display format for date and time values.Also controls interpretation of ambiguous date inputs.
#IntervalStyle                       =  postgres                            # {postgres,postgres_verbose,sql_standard,iso_8601}              Sets the display format for interval values.
#TimeZone                            =  'GMT'                               #                                                                Sets the time zone for displaying and interpreting time stamps.
#client_encoding                     =  'SQL_ASCII'                         #                                                                Sets the client's character set encoding.
#extra_float_digits                  =  0                                   # -15 to 3                                                       Sets the number of digits displayed for floating-point values.This affects real, double precision, and geometric data types. The parameter value is added to the standard number of digits (FLT_DIG or DBL_DIG as appropriate).
#lc_collate                          =  'C'                                 #                                                                Shows the collation order locale.
#lc_ctype                            =  'C'                                 #                                                                Shows the character classification and case conversion locale.
#server_encoding                     =  'SQL_ASCII'                         #                                                                Sets the server (database) character set encoding.
#timezone_abbreviations              =  ''                                  #                                                                Selects a file of time zone abbreviations.

Usage:

SELECT f_save_postgresql_conf('work_mem','10MB');

Final considerations:

There are some settings that need postgres to be restarted to get in production (like max_connections ), but the function will persists the new setting's value, and is up to you restart the server later.

The postgresql.conf file will be replaced by a new one, so any comment made directly in the file will be lost.

Feel free to use it (and improve it) and leave a comment if you find something wrong.