Обсуждение: Re: how to store more than 3 MB of character data in Postgres
Vadivel Subramaniam wrote:
>
> I assume, it could not be a problem with ODBC. I am able to store 2.5 MB of
> data into Oracle using the same ODBC APIs.
Well, it certainly isn't to do with PG itself:
$ cat bigtest.pl
#!/usr/bin/perl
print "CREATE TABLE foo (a int, b varchar);\n";
print "INSERT INTO foo VALUES (1, '".('a' x 5000000)."');\n";
$ perl bigtest.pl | psql -Urichardh richardh
CREATE TABLE
INSERT 3634376 1
$ psql -Urichardh richardh
richardh=> SELECT a,length(b) FROM foo; a | length
---+--------- 1 | 5000000
(1 row)
> Only difference is that Oracle supports CLOB datatype, that is mapped to
> LONG VARCHAR in ODBC.
> The input parameter during insert is bound using the below ODBC API
> retStatus = SQLBindParameter(dStmtHandle, 1, SQL_PARAM_INPUT,
> SQL_C_CHAR, SQL_LONGVARCHAR, dLen, 1, pData, 0, &dLen);
>
> For PostGres also the same API is used. Here varchar/text at the Postgres
> schema is mapped to LONGVARCHAR at ODBC.
> We can not go for bytea etc, since the data is in character format.
>
> I tried using "text" also at the postgres schema, still the impact is same
> (only stores around 64K).
> Could you please provide some example, how the large character data ( more
> than 1 MB ) can be inserted to text/varchar (in PostGres) using ODBC?
Hmm - looking back at your original email, I see you're using the
UnixODBC driver. Might be worth trying the PG version:
http://gborg.postgresql.org/project/psqlodbc/genpage.php?downloads
First step though, should be to check whether there are any
configuration settings that apply to longvarchar, because it sounds like
the odbc driver should be mapping to that.
I can't help you with finding those settings, since I have only ever
used the "official" PG driver on Windows.
-- Richard Huxton Archonet Ltd
Hi All! What is faster - SLECTion data from one large table (200 000 - 300 000 records), or SELECTion from a few small tables (example, 2 tables 150 000 records each)? Thank You
ON.KG wrote: > Hi All! > > What is faster - SLECTion data from one large table (200 000 - 300 000 > records), or SELECTion from a few small tables (example, 2 tables 150 > 000 records each)? It depends. Are you selecting all records? One record? A few records? If one or a few, do you have a suitable index on the table(s)? Is the table clustered? Expected to be cached in RAM? Do you have a specific problem, or reason to believe you may encounter one? -- Richard Huxton Archonet Ltd
Hi All! >> What is faster - SLECTion data from one large table (200 000 - 300 000 >> records), or SELECTion from a few small tables (example, 2 tables 150 >> 000 records each)? RH> It depends. Are you selecting all records? One record? A few records? If RH> one or a few, do you have a suitable index on the table(s)? Is the table RH> clustered? Expected to be cached in RAM? RH> Do you have a specific problem, or reason to believe you may encounter one? It's a real problem For example i have two large tables Structure of tables is same - has two fields - id, ip Now i'm using two selection from each in one transaction Each of them selects only one record selection clase like WHERE ip = 'xxx.xxx.xxx.xxx' so it is searches existance of IP in each table tables are clustered about cached in RAM - i'm novice in Postgresql - how does it work? now i need to make much faster as it is possible and have an idea just merge two tables in one - will it help me? Thank You
ON.KG wrote: > Hi All! > >>>What is faster - SLECTion data from one large table (200 000 - 300 000 >>>records), or SELECTion from a few small tables (example, 2 tables 150 >>>000 records each)? > > RH> It depends. Are you selecting all records? One record? A few records? If > RH> one or a few, do you have a suitable index on the table(s)? Is the table > RH> clustered? Expected to be cached in RAM? > > RH> Do you have a specific problem, or reason to believe you may encounter one? > > It's a real problem > > For example i have two large tables > Structure of tables is same - has two fields - id, ip > > Now i'm using two selection from each in one transaction > Each of them selects only one record > selection clase like WHERE ip = 'xxx.xxx.xxx.xxx' > so it is searches existance of IP in each table > > tables are clustered OK - so the tables aren't updated frequently, I assume. Do you have an index on "ip"? > about cached in RAM - i'm novice in Postgresql - how does it work? The operating-system will keep frequently used disk-blocks in memory. You don't have to do anything. Have you done any performance tuning in your postgresql.conf file? If not, try reading: http://www.powerpostgresql.com/PerfList > now i need to make much faster as it is possible > and have an idea just merge two tables in one - will it help me? If they hold the same information, they probably shouldn't have been split in the first place. -- Richard Huxton Archonet Ltd
RH> ON.KG wrote: >> Hi All! >> >>>>What is faster - SLECTion data from one large table (200 000 - 300 000 >>>>records), or SELECTion from a few small tables (example, 2 tables 150 >>>>000 records each)? >> >> For example i have two large tables >> Structure of tables is same - has two fields - id, ip >> >> Now i'm using two selection from each in one transaction >> Each of them selects only one record >> selection clase like WHERE ip = 'xxx.xxx.xxx.xxx' >> so it is searches existance of IP in each table >> >> tables are clustered RH> OK - so the tables aren't updated frequently, I assume. Do you have an RH> index on "ip"? Yes >> about cached in RAM - i'm novice in Postgresql - how does it work? RH> The operating-system will keep frequently used disk-blocks in memory. RH> You don't have to do anything. Have you done any performance tuning in RH> your postgresql.conf file? If not, try reading: RH> http://www.powerpostgresql.com/PerfList Server Administrator says, he did >> now i need to make much faster as it is possible >> and have an idea just merge two tables in one - will it help me? RH> If they hold the same information, they probably shouldn't have been RH> split in the first place. Content of tables is not absolutely same One has one kind of IPs, second - others And there's one more addition in question - if I will merge tables, in new table will be set new additional field - `type` char - to determine type of IP Thank You
O ON.KG έγραψε στις Jun 7, 2005 : > RH> ON.KG wrote: > >> Hi All! > >> > >>>>What is faster - SLECTion data from one large table (200 000 - 300 000 > >>>>records), or SELECTion from a few small tables (example, 2 tables 150 > >>>>000 records each)? > >> > >> For example i have two large tables > >> Structure of tables is same - has two fields - id, ip > >> > >> Now i'm using two selection from each in one transaction > >> Each of them selects only one record > >> selection clase like WHERE ip = 'xxx.xxx.xxx.xxx' > >> so it is searches existance of IP in each table > >> > >> tables are clustered > > RH> OK - so the tables aren't updated frequently, I assume. Do you have an > RH> index on "ip"? > > Yes > > >> about cached in RAM - i'm novice in Postgresql - how does it work? > > RH> The operating-system will keep frequently used disk-blocks in memory. > RH> You don't have to do anything. Have you done any performance tuning in > RH> your postgresql.conf file? If not, try reading: > RH> http://www.powerpostgresql.com/PerfList > > Server Administrator says, he did > > >> now i need to make much faster as it is possible > >> and have an idea just merge two tables in one - will it help me? > > RH> If they hold the same information, they probably shouldn't have been > RH> split in the first place. > > Content of tables is not absolutely same > One has one kind of IPs, second - others > > And there's one more addition in question - if I will merge tables, > in new table will be set new additional field - `type` char - to > determine type of IP > > Thank You Just a thought, also you could try if converting your ip from varchar(32) to int8 (unsigned int4) would make any difference, since the index on int8 would be more efficient. > > > ---------------------------(end of broadcast)--------------------------- > TIP 9: the planner will ignore your desire to choose an index scan if your > joining column's datatypes do not match > -- -Achilleus