Prefazione o cumu hè ghjunta l'idea di seccione
A storia principia quì: Dopu à quasi tutti i risorsi per ottimisà a dumanda, à quellu tempu, eranu esauriti, a quistione hè stata - chì dopu? Hè cusì chì l'idea di particione hè nata.
Digressione lirica:
Precisamente 'à quellu mumentu', perchè ... Grazie è Habru !
Allora, cumu pudete fà u cliente felice, è à u stessu tempu migliurà e vostre capacità?
Per simplificà tuttu u più pussibule, allora ci sò solu dui modi per migliurà radicalmente qualcosa in u rendiment di a basa di dati:
1) Percorsu estensivu - aumentemu e risorse, cambià a cunfigurazione;
2) Percorsu intensivu - ottimisazione di quistione
Siccomu, ripetu, à quellu tempu ùn era più chjaru chì altru cambià in a dumanda di accelerà, a strada hè stata scelta - cambiamenti in u disignu di a tavola.
Allora, a quistione principale hè: chì è cumu cambiamu?
Cundizioni iniziali
Prima, ci hè questu ERD (mostratu in modu simplificatu cundizionalmente):
Principi caratteristiche:
- rilazioni assai à parechji
- a tavula hà digià una chjave di partizione potenziale
Richiesta originale:
SELECT
p."PARAMETER_ID" as parameter_id,
pc."PC_NAME" AS pc_name,
pc."CUSTOMER_PARTNUMBER" AS customer_partnumber,
w."LASERMARK" AS lasermark,
w."LOTID" AS lotid,
w."REPORTED_VALUE" AS reported_value,
w."LOWER_SPEC_LIMIT" AS lower_spec_limit,
w."UPPER_SPEC_LIMIT" AS upper_spec_limit,
p."TYPE_CALCUL" AS type_calcul,
s."SHIPMENT_NAME" AS shipment_name,
s."SHIPMENT_DATE" AS shipment_date,
extract(year from s."SHIPMENT_DATE") AS year,
extract(month from s."SHIPMENT_DATE") as month,
s."REPORT_NAME" AS report_name,
p."SPARAM_NAME" AS SPARAM_name,
p."CUSTOMERPARAM_NAME" AS customerparam_name
FROM data w INNER JOIN shipment s ON s."SHIPMENT_ID" = w."SHIPMENT_ID"
INNER JOIN parameters p ON p."PARAMETER_ID" = w."PARAMETER_ID"
INNER JOIN shipment_pc sp ON s."SHIPMENT_ID" = sp."SHIPMENT_ID"
INNER JOIN pc pc ON pc."PC_ID" = sp."PC_ID"
INNER JOIN ( SELECT w2."LASERMARK" , MAX(s2."SHIPMENT_DATE") AS "SHIPMENT_DATE"
FROM shipment s2 INNER JOIN data w2 ON s2."SHIPMENT_ID" = w2."SHIPMENT_ID"
GROUP BY w2."LASERMARK"
) md ON md."SHIPMENT_DATE" = s."SHIPMENT_DATE" AND md."LASERMARK" = w."LASERMARK"
WHERE
s."SHIPMENT_DATE" >= '2018-07-01' AND s."SHIPMENT_DATE" <= '2018-09-30' ;
Risultati di l'esecuzione nantu à a basa di dati di teste:
Tiuccia : 502 997.55
Tempu di esecuzione: 505 seconde.
Chì vedemu ? Una dumanda regulare, basatu annantu à una fetta di tempu.
Facemu l'assunzione logica più simplice: se ci hè una mostra di una fetta di tempu, ci aiuterà? Hè ghjustu - partitioning.
Cosa à seccione?
À u primu sguardu, l'scelta hè ovvia - a partizione dichjarazione di a tavola "spedizione" utilizendu a chjave "SHIPMENT_DATE" (saltà troppu avanti - à a fine hè stata un pocu sbagliatu in a produzzione).
Cumu si sparte ?
Sta quistione hè dinù micca troppu difficiule. Fortunatamente, in PostgreSQL 10, ci hè avà un mecanismu di particionamentu umanu.
So:
- Salvà un dump di a tavola fonte - pg_dump source_table
- Elimine u tavulu originale - drop table source_table
- Crea una tavola parent cù a partizione di intervalli - creà table source_table
- Crea sezioni - create table source_table, create index
- Importa u dump creatu in u passu 1 - pg_restore
Scripts per a particione
Per simplicità è comodità, i passi 2,3,4 sò stati cumminati in un script.
So:
Salvà un dump di a tavola fonte
pg_dump postgres --file=/dump/shipment.dmp --format=c --table=shipment --verbose > /dump/shipment.log 2>&1Sguassà a tavula fonte + Crea una tavola parent cù partizioni di intervallu + Crea partizioni
--create_partition_shipment.sql
do language plpgsql $$
declare
rec_shipment_date RECORD ;
partition_name varchar;
index_name varchar;
current_year varchar ;
current_month varchar ;
begin_year varchar ;
begin_month varchar ;
next_year varchar ;
next_month varchar ;
first_flag boolean ;
i integer ;
begin
RAISE NOTICE 'CREATE TEMPORARY TABLE FOR SHIPMENT_DATE';
CREATE TEMP TABLE tmp_shipment_date as select distinct "SHIPMENT_DATE" from shipment order by "SHIPMENT_DATE" ;
RAISE NOTICE 'DROP TABLE shipment';
drop table shipment cascade ;
CREATE TABLE public.shipment
(
"SHIPMENT_ID" integer NOT NULL DEFAULT nextval('shipment_shipment_id_seq'::regclass),
"SHIPMENT_NAME" character varying(30) COLLATE pg_catalog."default",
"SHIPMENT_DATE" timestamp without time zone,
"REPORT_NAME" character varying(40) COLLATE pg_catalog."default"
)
PARTITION BY RANGE ("SHIPMENT_DATE")
WITH (
OIDS = FALSE
)
TABLESPACE pg_default;
RAISE NOTICE 'CREATE PARTITIONS FOR TABLE shipment';
current_year:='0';
current_month:='0';
begin_year := '0' ;
begin_month := '0' ;
next_year := '0' ;
next_month := '0' ;
FOR rec_shipment_date IN SELECT * FROM tmp_shipment_date LOOP
RAISE NOTICE 'SHIPMENT_DATE=%',rec_shipment_date."SHIPMENT_DATE";
current_year := date_part('year' ,rec_shipment_date."SHIPMENT_DATE");
current_month := date_part('month' ,rec_shipment_date."SHIPMENT_DATE") ;
IF to_number(current_month,'99') < 10 THEN
current_month := '0'||current_month ;
END IF ;
--Init borders
IF begin_year = '0' THEN
first_flag := true ; --first time flag
begin_year := current_year ;
begin_month := current_month ;
IF current_month = '12' THEN
next_year := date_part('year' ,rec_shipment_date."SHIPMENT_DATE" + interval '1 year') ;
ELSE
next_year := current_year ;
END IF;
next_month := date_part('month' ,rec_shipment_date."SHIPMENT_DATE" + interval '1 month') ;
END IF;
-- Check current date into borders NOT for First time
IF to_date( current_year||'.'||current_month, 'YYYY.MM') >= to_date( begin_year||'.'||begin_month, 'YYYY.MM') AND
to_date( current_year||'.'||current_month, 'YYYY.MM') < to_date( next_year||'.'||next_month, 'YYYY.MM') AND
NOT first_flag
THEN
CONTINUE ;
ELSE
--NEW borders only for second and after time
begin_year := current_year ;
begin_month := current_month ;
IF current_month = '12' THEN
next_year := date_part('year' ,rec_shipment_date."SHIPMENT_DATE" + interval '1 year') ;
ELSE
next_year := current_year ;
END IF;
next_month := date_part('month' ,rec_shipment_date."SHIPMENT_DATE" + interval '1 month') ;
END IF;
partition_name := 'shipment_shipment_date_'||begin_year||'-'||begin_month||'-01-'|| next_year||'-'||next_month||'-01' ;
EXECUTE format('CREATE TABLE ' || quote_ident(partition_name) || ' PARTITION OF shipment FOR VALUES FROM ( %L ) TO ( %L ) ' , current_year||'-'||current_month||'-01' , next_year||'-'||next_month||'-01' ) ;
index_name := partition_name||'_shipment_id_idx';
RAISE NOTICE 'INDEX NAME =%',index_name;
EXECUTE format('CREATE INDEX ' || quote_ident(index_name) || ' ON '|| quote_ident(partition_name) ||' USING btree ("SHIPMENT_ID") TABLESPACE pg_default ' ) ;
--Drop first time flag
first_flag := false ;
END LOOP;
end
$$;Importà u dump
pg_restore -d postgres --data-only --format=c --table=shipment --verbose shipment.dmp > /tmp/data_dump/shipment_restore.log 2>&1Cuntrollà i risultati di partitioning
Chì avemu un risultatu? U testu sanu di u pianu di esecutivu hè grande è noioso, cusì hè abbastanza pussibule di limità à i numeri finali.
Hè statu
Cost: 502 997.55
Tempu di esecuzione: seconde 505.
Hè diventatu
Cost: 77 872.36
Tempu di esecuzione: seconde 79.
Un bellu risultatu. Costu riduttu è tempu di esecuzione. Cusì, l'usu di partizioni dà l'effettu previstu è, in generale, senza sorprese.
Fate u cliente felice
I risultati di a prova sò stati presentati à u cliente per rivisione. È dopu avè rivisatu, sò stati datu un verdict un pocu inesperu: "Great, sparte the "data" table.
Iè, ma avemu esaminatu una tavola "spedizione" completamente diversa; a tavola "dati" ùn hà micca u campu "SHIPMENT_DATE".
Nisun prublema, aghjunghje, cambià. A cosa principal hè chì u cliente hè cuntentu di u risultatu, i dettagli di implementazione ùn sò micca particularmente impurtanti.
Particionà a tabella principale "dati"
In generale, ùn ci sò micca difficultà particulari. Ancu s'ellu, l'algoritmu di partizione, di sicuru, hà cambiatu un pocu.
Aghjunghjendu a colonna "SHIPMENT_DATA" à a tavula "dati".
psql -h хост -U база -d юзер
=> ALTER TABLE data ADD COLUMN "SHIPMENT_DATE" timestamp without time zone ;Inserite i valori di a colonna "SHIPMENT_DATA" in a tavola "dati" cù i valori di a colonna di u listessu nome da a tavola "spedizione"
-----------------------------
--update_data.sql
--updating for altered table "data" to values of "shipment_data" from the table "shipment"
--version 1.0
do language plpgsql $$
declare
rec_shipment_data RECORD ;
shipment_date timestamp without time zone ;
row_count integer ;
total_rows integer ;
begin
select count(*) into total_rows from shipment ;
RAISE NOTICE 'Total %',total_rows;
row_count:= 0 ;
FOR rec_shipment_data IN SELECT * FROM shipment LOOP
update data set "SHIPMENT_DATE" = rec_shipment_data."SHIPMENT_DATE" where "SHIPMENT_ID" = rec_shipment_data."SHIPMENT_ID";
row_count:= row_count +1 ;
RAISE NOTICE 'row count = % , from %',row_count,total_rows;
END LOOP;
end
$$;Salvà un dump di a tavola "dati".
pg_dump postgres --file=/dump/data.dmp --format=c --table=data --verbose > /dump/data.log 2>&1</sourceRicreate a tavola partizionata "dati"
--create_partition_data.sql
--create partitions for the table "wafer data" by range column "shipment_data" with one month duration
--version 1.0
do language plpgsql $$
declare
rec_shipment_date RECORD ;
partition_name varchar;
index_name varchar;
current_year varchar ;
current_month varchar ;
begin_year varchar ;
begin_month varchar ;
next_year varchar ;
next_month varchar ;
first_flag boolean ;
i integer ;
begin
RAISE NOTICE 'CREATE TEMPORARY TABLE FOR SHIPMENT_DATE';
CREATE TEMP TABLE tmp_shipment_date as select distinct "SHIPMENT_DATE" from shipment order by "SHIPMENT_DATE" ;
RAISE NOTICE 'DROP TABLE data';
drop table data cascade ;
RAISE NOTICE 'CREATE PARTITIONED TABLE data';
CREATE TABLE public.data
(
"RUN_ID" integer,
"LASERMARK" character varying(20) COLLATE pg_catalog."default" NOT NULL,
"LOTID" character varying(80) COLLATE pg_catalog."default",
"SHIPMENT_ID" integer NOT NULL,
"PARAMETER_ID" integer NOT NULL,
"INTERNAL_VALUE" character varying(75) COLLATE pg_catalog."default",
"REPORTED_VALUE" character varying(75) COLLATE pg_catalog."default",
"LOWER_SPEC_LIMIT" numeric,
"UPPER_SPEC_LIMIT" numeric ,
"SHIPMENT_DATE" timestamp without time zone
)
PARTITION BY RANGE ("SHIPMENT_DATE")
WITH (
OIDS = FALSE
)
TABLESPACE pg_default ;
RAISE NOTICE 'CREATE PARTITIONS FOR TABLE data';
current_year:='0';
current_month:='0';
begin_year := '0' ;
begin_month := '0' ;
next_year := '0' ;
next_month := '0' ;
i := 1;
FOR rec_shipment_date IN SELECT * FROM tmp_shipment_date LOOP
RAISE NOTICE 'SHIPMENT_DATE=%',rec_shipment_date."SHIPMENT_DATE";
current_year := date_part('year' ,rec_shipment_date."SHIPMENT_DATE");
current_month := date_part('month' ,rec_shipment_date."SHIPMENT_DATE") ;
--Init borders
IF begin_year = '0' THEN
RAISE NOTICE '***Init borders';
first_flag := true ; --first time flag
begin_year := current_year ;
begin_month := current_month ;
IF current_month = '12' THEN
next_year := date_part('year' ,rec_shipment_date."SHIPMENT_DATE" + interval '1 year') ;
ELSE
next_year := current_year ;
END IF;
next_month := date_part('month' ,rec_shipment_date."SHIPMENT_DATE" + interval '1 month') ;
END IF;
-- RAISE NOTICE 'current_year=% , current_month=% ',current_year,current_month;
-- RAISE NOTICE 'begin_year=% , begin_month=% ',begin_year,begin_month;
-- RAISE NOTICE 'next_year=% , next_month=% ',next_year,next_month;
-- Check current date into borders NOT for First time
RAISE NOTICE 'Current data = %',to_char( to_date( current_year||'.'||current_month, 'YYYY.MM'), 'YYYY.MM');
RAISE NOTICE 'Begin data = %',to_char( to_date( begin_year||'.'||begin_month, 'YYYY.MM'), 'YYYY.MM');
RAISE NOTICE 'Next data = %',to_char( to_date( next_year||'.'||next_month, 'YYYY.MM'), 'YYYY.MM');
IF to_date( current_year||'.'||current_month, 'YYYY.MM') >= to_date( begin_year||'.'||begin_month, 'YYYY.MM') AND
to_date( current_year||'.'||current_month, 'YYYY.MM') < to_date( next_year||'.'||next_month, 'YYYY.MM') AND
NOT first_flag
THEN
RAISE NOTICE '***CONTINUE';
CONTINUE ;
ELSE
--NEW borders only for second and after time
RAISE NOTICE '***NEW BORDERS';
begin_year := current_year ;
begin_month := current_month ;
IF current_month = '12' THEN
next_year := date_part('year' ,rec_shipment_date."SHIPMENT_DATE" + interval '1 year') ;
ELSE
next_year := current_year ;
END IF;
next_month := date_part('month' ,rec_shipment_date."SHIPMENT_DATE" + interval '1 month') ;
END IF;
IF to_number(current_month,'99') < 10 THEN
current_month := '0'||current_month ;
END IF ;
IF to_number(begin_month,'99') < 10 THEN
begin_month := '0'||begin_month ;
END IF ;
IF to_number(next_month,'99') < 10 THEN
next_month := '0'||next_month ;
END IF ;
RAISE NOTICE 'current_year=% , current_month=% ',current_year,current_month;
RAISE NOTICE 'begin_year=% , begin_month=% ',begin_year,begin_month;
RAISE NOTICE 'next_year=% , next_month=% ',next_year,next_month;
partition_name := 'data_'||begin_year||begin_month||'01_'||next_year||next_month||'01' ;
RAISE NOTICE 'PARTITION NUMBER % , TABLE NAME =%',i , partition_name;
EXECUTE format('CREATE TABLE ' || quote_ident(partition_name) || ' PARTITION OF data FOR VALUES FROM ( %L ) TO ( %L ) ' , begin_year||'-'||begin_month||'-01' , next_year||'-'||next_month||'-01' ) ;
index_name := partition_name||'_shipment_id_parameter_id_idx';
RAISE NOTICE 'INDEX NAME =%',index_name;
EXECUTE format('CREATE INDEX ' || quote_ident(index_name) || ' ON '|| quote_ident(partition_name) ||' USING btree ("SHIPMENT_ID", "PARAMETER_ID") TABLESPACE pg_default ' ) ;
index_name := partition_name||'_lasermark_idx';
RAISE NOTICE 'INDEX NAME =%',index_name;
EXECUTE format('CREATE INDEX ' || quote_ident(index_name) || ' ON '|| quote_ident(partition_name) ||' USING btree ("LASERMARK" COLLATE pg_catalog."default") TABLESPACE pg_default ' ) ;
index_name := partition_name||'_shipment_id_idx';
RAISE NOTICE 'INDEX NAME =%',index_name;
EXECUTE format('CREATE INDEX ' || quote_ident(index_name) || ' ON '|| quote_ident(partition_name) ||' USING btree ("SHIPMENT_ID") TABLESPACE pg_default ' ) ;
index_name := partition_name||'_parameter_id_idx';
RAISE NOTICE 'INDEX NAME =%',index_name;
EXECUTE format('CREATE INDEX ' || quote_ident(index_name) || ' ON '|| quote_ident(partition_name) ||' USING btree ("PARAMETER_ID") TABLESPACE pg_default ' ) ;
index_name := partition_name||'_shipment_date_idx';
RAISE NOTICE 'INDEX NAME =%',index_name;
EXECUTE format('CREATE INDEX ' || quote_ident(index_name) || ' ON '|| quote_ident(partition_name) ||' USING btree ("SHIPMENT_DATE") TABLESPACE pg_default ' ) ;
--Drop first time flag
first_flag := false ;
END LOOP;
end
$$;
Caricate u dump creatu in u passu 3.
pg_restore -h хост -юзер -d база --data-only --format=c --table=data --verbose data.dmp > data_restore.log 2>&1Crea una sezione separata per i dati antichi
---------------------------------------------------
--create_partition_for_old_dates.sql
--create partitions for keeping old dates
--version 1.0
do language plpgsql $$
declare
rec_shipment_date RECORD ;
partition_name varchar;
index_name varchar;
begin
SELECT min("SHIPMENT_DATE") AS min_date INTO rec_shipment_date from data ;
RAISE NOTICE 'Old date is %',rec_shipment_date.min_date ;
partition_name := 'data_old_dates' ;
RAISE NOTICE 'PARTITION NAME IS %',partition_name;
EXECUTE format('CREATE TABLE ' || quote_ident(partition_name) || ' PARTITION OF data FOR VALUES FROM ( %L ) TO ( %L ) ' , '1900-01-01' ,
to_char( rec_shipment_date.min_date,'YYYY')||'-'||to_char(rec_shipment_date.min_date,'MM')||'-01' ) ;
index_name := partition_name||'_shipment_id_parameter_id_idx';
EXECUTE format('CREATE INDEX ' || quote_ident(index_name) || ' ON '|| quote_ident(partition_name) ||' USING btree ("SHIPMENT_ID", "PARAMETER_ID") TABLESPACE pg_default ' ) ;
index_name := partition_name||'_lasermark_idx';
EXECUTE format('CREATE INDEX ' || quote_ident(index_name) || ' ON '|| quote_ident(partition_name) ||' USING btree ("LASERMARK" COLLATE pg_catalog."default") TABLESPACE pg_default ' ) ;
index_name := partition_name||'_shipment_id_idx';
EXECUTE format('CREATE INDEX ' || quote_ident(index_name) || ' ON '|| quote_ident(partition_name) ||' USING btree ("SHIPMENT_ID") TABLESPACE pg_default ' ) ;
index_name := partition_name||'_parameter_id_idx';
EXECUTE format('CREATE INDEX ' || quote_ident(index_name) || ' ON '|| quote_ident(partition_name) ||' USING btree ("PARAMETER_ID") TABLESPACE pg_default ' ) ;
index_name := partition_name||'_shipment_date_idx';
EXECUTE format('CREATE INDEX ' || quote_ident(index_name) || ' ON '|| quote_ident(partition_name) ||' USING btree ("SHIPMENT_DATE") TABLESPACE pg_default ' ) ;
end
$$;Risultati finali:
Hè statu
Cost: 502 997.55
Tempu di esecuzione: 505 seconde.
Hè diventatu
Cost: 68 533.70
Tempu di esecuzione: seconde 69
Degnu, abbastanza degnu. E cunsiderendu chì in u caminu avemu riesciutu à più o menu maestru di u mecanismu di partizione in PostgreSQL 10 - un risultatu eccellente.
Digressione lirica
Hè pussibule di fà ancu megliu - SI, PUdite!Per fà questu, avete bisognu di utilizà VISUALIZZA MATERIALIZZATA.
CREATE VISUALIZZA MATERIALIZZATA LASERMARK_VIEW
CREATE MATERIALIZED VIEW LASERMARK_VIEW
AS
SELECT w."LASERMARK" , MAX(s."SHIPMENT_DATE") AS "SHIPMENT_DATE"
FROM shipment s INNER JOIN data w ON s."SHIPMENT_ID" = w."SHIPMENT_ID"
GROUP BY w."LASERMARK" ;
CREATE INDEX lasermark_vw_shipment_date_ind on lasermark_view USING btree ("SHIPMENT_DATE") TABLESPACE pg_default;
analyze lasermark_view ;
Una volta riscrivimu a dumanda:
Query usendu vista materializzata
SELECT
p."PARAMETER_ID" as parameter_id,
pc."PC_NAME" AS pc_name,
pc."CUSTOMER_PARTNUMBER" AS customer_partnumber,
w."LASERMARK" AS lasermark,
w."LOTID" AS lotid,
w."REPORTED_VALUE" AS reported_value,
w."LOWER_SPEC_LIMIT" AS lower_spec_limit,
w."UPPER_SPEC_LIMIT" AS upper_spec_limit,
p."TYPE_CALCUL" AS type_calcul,
s."SHIPMENT_NAME" AS shipment_name,
s."SHIPMENT_DATE" AS shipment_date,
extract(year from s."SHIPMENT_DATE") AS year,
extract(month from s."SHIPMENT_DATE") as month,
s."REPORT_NAME" AS report_name,
p."STC_NAME" AS STC_name,
p."CUSTOMERPARAM_NAME" AS customerparam_name
FROM data w INNER JOIN shipment s ON s."SHIPMENT_ID" = w."SHIPMENT_ID"
INNER JOIN parameters p ON p."PARAMETER_ID" = w."PARAMETER_ID"
INNER JOIN shipment_pc sp ON s."SHIPMENT_ID" = sp."SHIPMENT_ID"
INNER JOIN pc pc ON pc."PC_ID" = sp."PC_ID"
INNER JOIN LASERMARK_VIEW md ON md."SHIPMENT_DATE" = s."SHIPMENT_DATE" AND md."LASERMARK" = w."LASERMARK"
WHERE
s."SHIPMENT_DATE" >= '2018-07-01' AND s."SHIPMENT_DATE" <= '2018-09-30';
È avemu un altru risultatu:
Hè statu
Cost: 502 997.55
Tempu di esecuzione: 505 seconde
Hè diventatu
Cost: 42 481.16
Tempu di esecuzione: seconde 43.
Ancu s'ellu, sicuru, un risultatu cusì promettente hè ingannevole; l'idee anu da esse rinfriscate. Allora u tempu tutale per riceve dati ùn aiuterà micca assai. Ma cum'è un esperimentu hè abbastanza interessante.
In verità, cum'è hè risultatu, grazie di novu è Habru!-
Afterword
Dunque, u cliente hè cuntentu. È bisognu prufittà di a situazione.
Novu compitu: Chì pudete vene per approfondisce è espansione ?
E poi mi ricordu - ragazzi, ùn avemu micca monitoraghju di e nostre basa di dati PostgreSQL.
A manu nantu à u core, ci hè ancu qualchì monitoraghju in forma di Cloud Watch in AWS. Ma chì hè u benefiziu di stu monitoraghju per u DBA? In generale, praticamenti nimu.
Sì avete l'uppurtunità di fà qualcosa utile è interessante per voi stessu, ùn pudete micca prufittà di sta chance ...
PER
Eccu cumu venemu à a parte più interessante:
3 di dicembre di u 2018.
Piglià a decisione di inizià a ricerca nantu à e capacità dispunibili per monitorizà u rendiment di e dumande PostgreSQL.
Ma hè una storia completamente diversa.
À seguità…
Source: www.habr.com