Postgresql – Inserting into related tables

auto-incrementcteinsertpostgresql

I have a database setup with the following schema:

CREATE TABLE siteInfo (
    siteID             SERIAL  NOT NULL,
    siteName           TEXT    NOT NULL,
    siteHost           TEXT    NOT NULL,
    notes              TEXT    NOT NULL,
    allowableCountries TEXT    NOT NULL,
    displayChance      INT     NOT NULL,
    imagePath          TEXT    NOT NULL,
    PRIMARY KEY (siteID)
);

CREATE TABLE siteLinks (
    siteID             SERIAL  NOT NULL,
    URL                TEXT    NOT NULL,
    FOREIGN KEY (siteID) REFERENCES siteInfo(siteID) ON DELETE CASCADE
);

CREATE TABLE siteDemographicLinks (
    siteID             SERIAL  NOT NULL,
    URL                TEXT    NOT NULL,
    country            TEXT    NOT NULL,
    chance             INT     NOT NULL,
    FOREIGN KEY (siteID) REFERENCES siteInfo(siteID) ON DELETE CASCADE
);

CREATE TABLE linkVisits (
    siteID             SERIAL  NOT NULL,
    rawVisit           BIGINT  NOT NULL,
    redirects          BIGINT  NOT NULL,
    FOREIGN KEY (siteID) REFERENCES siteInfo(siteID) ON DELETE CASCADE
);

Data from my form is in the following format:

array(7) {
["siteName"]=>string(9) "Site Name"
["siteHost"]=>string(9) "SIte Host"
["notes"]=>string(5) "Notes"
["links"]=>array(2) {[0]=>string(6) "Link 1" [1]=>string(6) "Link 2"}
["countries"]=>string(4) "None"
["displayChance"]=>string(2) "15"
["extraLink"]=>array(2) {
   [0]=>array(3) {
      ["url"]=>string(7) "dSite 1"
      ["countries"]=>string(4) "NONE"
      ["chance"]=>string(2) "11"
      }
   [1]=>array(3) {
      ["url"]=>string(6) "dSite2"
      ["countries"]=>string(4) "None"
      ["chance"]=>string(2) "13"
      }
   }
}

How would I go abound inserting data into the many type tables so they reference tuples inserted into the one type table?

I have this query constructed:

INSERT INTO siteInfo (siteName, siteHost, notes, allowableCountries, displayChance, imagePath)
VALUES ('Sample', 'sample.com', 'note', 'NONE', '50', '../var');

I would then need to insert data into the siteLinks table, which is related to the entry already in the siteInfo table.

INSERT INTO siteLinks (siteID, URL)
VALUES ((SELECT siteid FROM siteinfo WHERE sitename='Sample'), 'test');

Is there a better way of doing this?

Best Answer

Chain your insert with data-modifying CTEs:

WITH ins0 AS (
   INSERT INTO siteInfo (siteName, siteHost, notes, ... )
   VALUES ('Sample', 'sample.com', 'note', ... );
   RETURNING siteid
   )
INSERT INTO siteLinks (siteID, URL)
SELECT siteid, 'test'
FROM   ins0;

Or use lastval() or currval():

BEGIN;

INSERT INTO siteInfo (siteName, siteHost, notes, ... )
VALUES ('Sample', 'sample.com', 'note', ... );

INSERT INTO siteLinks (siteID, URL)
VALUES (lastval(), 'test');

COMMIT;

Postgresql – Postgres multiple joins slow query, how to store default child record

You write:

Each customer can have multiple sites, but only one should be displayed in this list.

Yet, your query retrieves all rows. That would be a point to optimize. But you also do not define which site is to be picked.

Either way, it does not matter much here. Your EXPLAIN shows only 5026 rows for the site scan (5018 for the customer scan). So hardly any customer actually has more than one site. Did you ANALYZE your tables before running EXPLAIN?

From the numbers I see in your EXPLAIN, indexes will give you nothing for this query. Sequential table scans will be the fastest possible way. Half a second is rather slow for 5000 rows, though. Maybe your database needs some general performance tuning?

Maybe the query itself is faster, but "half a second" includes network transfer? EXPLAIN ANALYZE would tell us more.

If this query is your bottleneck, I would suggest you implement a materialized view.

After you provided more information I find that my diagnosis pretty much holds.

The query itself needs 27 ms. Not much of a problem there. "Half a second" was the kind of misunderstanding I had suspected. The slow part is the network transfer (plus ssh encoding / decoding, possibly rendering). You should only retrieve 100 rows, that would solve most of it, even if it means to execute the whole query every time.

If you go the route with a materialized view like I proposed you could add a serial number without gaps to the table plus index on it - by adding a column row_number() OVER (<your sort citeria here>) AS mv_id.

Then you can query:

SELECT *
FROM   materialized_view
WHERE  mv_id >= 2700
AND    mv_id <  2800;

This will perform very fast. LIMIT / OFFSET cannot compete, that needs to compute the whole table before it can sort and pick 100 rows.

pgAdmin timing

When you execute a query from the query tool, the message pane shows something like:

Total query runtime: 62 ms.

And the status line shows the same time. I quote pgAdmin help about that:

The status line will show how long the last query took to complete. If a dataset was returned, not only the elapsed time for server execution is displayed, but also the time to retrieve the data from the server to the Data Output page.

If you want to see the time on the server you need to use SQL EXPLAIN ANALYZE or the built in Shift + F7keyboard shortcut or Query -> Explain analyze. Then, at the bottom of the explain output you get something like this:

Total runtime: 0.269 ms

Postgresql – Possible to have nested inserts in Postgres 8.4

You should be able to do something like this with a writable CTE:

WITH i AS (
   INSERT INTO host (hostname, hostrole) VALUES ('foobar', 'Virtual') RETURNING id
)
INSERT INTO interface (name, mac, host)
SELECT 'eth0', '00:50:56:9d:34:d4', id
FROM i

(untested, but it should be something like that)

Writable CTE is in PostgreSQL 9.1 and up.

Best Answer

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Postgresql – Postgres multiple joins slow query, how to store default child record

pgAdmin timing

Postgresql – Possible to have nested inserts in Postgres 8.4

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