I have this code:
declare
sName varchar(25);
iRank number := 0;
sDesc varchar(510);
cursor q is
SELECT *
FROM trec_topics ORDER BY num;
BEGIN
for ql in q
loop
sDesc := replace(replace(replace(ql.title, '?', '{?}'), ')', '{)}'), '(', '{(}');
--dbms_output.put_line(ql.num||'-'||sDesc);
declare
cursor c is
SELECT /*+ FIRST_ROWS(100) */ docno,
CASE
WHEN SCORE(10) >= SCORE(20) THEN SCORE(10)
ELSE SCORE(20)
END AS SCORE
FROM txt_search_docs WHERE CONTAINS(txt, 'DEFINESCORE(ql.title, OCCURRENCE)', 10) > 0 OR
CONTAINS(txt, 'DEFINESCORE(sDesc, OCCURRENCE)', 20) > 0
order by SCORE desc;
begin
iRank := 1;
for c1 in c
loop
dbms_output.put_line(ql.num||' Q0 '||c1.docno||' '||lpad(iRank,3, '0')||' '||lpad(c1.score, 2, '0')||' myUser');
iRank := iRank + 1;
exit when c%rowcount = 100;
end loop;
end;
end loop;
end;
As you can see I'm doing select on two different tables, however, I need to change the standard score, as it did not perform well. I'm trying to use the DEFINESCORE clause that has this 'DEFINESCORE (query_term, scoring_expression)' format.
How can I call the table columns within this clause? That is, I need to call my columns instead of "query_term", as there are several documents to do the search. Because the way I’m calling him, he’s looking for exactly the term ql.title
Anyone a suggestion to help me with this problem?
I finally managed to solve it.
It was about:
create a variable: topics varchar (525);
store the column value: topics := replace(replace(replace(ql.title, '?', '{?}'), ')', '{)}'), '(', '{(}');
and after calling it in the CONTAINS clause: FROM txt_search_docs WHERE CONTAINS(txt, 'DEFINESCORE(('''||topics||'''), OCCURRENCE)', 1) > 0
I try to run the next 2 queries sequentially. The first one runs perfectly, the second one throws
ORA-30926: unable to get a stable set of rows in the source tables
I searched the net for a solution but I can't replicate it for my queries. Can anyone help me please?
Query 1:
merge into sdc_compare_person dcip
using (
select anumber, position, character
from sdc_diakrietposities_cip
where kind = 'Surname'
) x
on (dcip.sourcekey = x.anumber)
when matched then update set
dcip.GESVOR = substr(dcip.GESVOR, 1, x.position - 1) ||
x.character ||
substr(dcip.GESVOR, x.position + 1, length(dcip.GESVOR)-x.position)
;
188 rows merged.
Query 2:
merge into sdc_compare_person dcip
using (
select anumber, position, character
from sdc_diakrietposities_cip
where kind = 'Lastname'
) x
on (dcip.sourcekey = x.anumber)
when matched then update set
dcip.GESNAM_D = substr(dcip.GESNAM_D, 1, x.position - 1) ||
x.character ||
substr(dcip.GESNAM_D, x.position + 1, length(dcip.GESNAM_D) - x.position)
;
SQL Error: ORA-30926: Unable to get a stable set of rows in the source tables
You can alway use ordinary update, it's not so elegant as MERGE, but should work:
UPDATE sdc_compare_person dcip
SET dcip.GESNAM_D = (
SELECT substr(dcip.GESNAM_D, 1, x.position - 1) ||
x.character ||
substr(dcip.GESNAM_D, x.position + 1, length(dcip.GESNAM_D) -
x.position)
FROM sdc_diakrietposities_cip x
where kind = 'Lastname'
AND dcip.sourcekey = x.anumber
)
WHERE dcip.sourcekey IN (
select anumber
from sdc_diakrietposities_cip
where kind = 'Lastname'
);
From the comments to the question it becomes clear that the author wants to update the same record many times.
Of course, this cannot get past ORA-30926 when trying to do it by a merge construct.
It's hard or impossible to do such a thing in pure oracle sql, but it's easily done with a pl/sql function.
For example:
create or replace function replace_chars(p_str varchar2, p_id number, p_kind varchar2) return varchar2 as
l_str varchar2(32767):=p_str;
begin
for u in (select u.position, u.character from sdc_diakrietposities_cip u
where u.anumber=p_id and u.kind=p_kind order by u.position) loop
if (u.position >= 1 or u.position <= length(l_str)) then
l_str:=substr(l_str, 1, u.position-1)|| u.character || substr(l_str, u.position+1);
end if;
end loop;
return l_str;
end;
Use like this:
update sdc_compare_person t
set t.GESNAM_D= replace_chars(t.GESNAM_D, t.sourcekey, 'Lastname');
I'd suggest backing up your table before running this.
I've seen a bunch of different solutions on StackOverflow that span many years and many Postgres versions, but with some of the newer features like gen_random_bytes I want to ask again to see if there is a simpler solution in newer versions.
Given IDs which contain a-zA-Z0-9, and vary in size depending on where they're used, like...
bTFTxFDPPq
tcgHAdW3BD
IIo11r9J0D
FUW5I8iCiS
uXolWvg49Co5EfCo
LOscuAZu37yV84Sa
YyrbwLTRDb01TmyE
HoQk3a6atGWRMCSA
HwHSZgGRStDMwnNXHk3FmLDEbWAHE1Q9
qgpDcrNSMg87ngwcXTaZ9iImoUmXhSAv
RVZjqdKvtoafLi1O5HlvlpJoKzGeKJYS
3Rls4DjWxJaLfIJyXIEpcjWuh51aHHtK
(Like the IDs that Stripe uses.)
How can you generate them randomly and safely (as far as reducing collisions and reducing predictability goes) with an easy way to specify different lengths for different use cases, in Postgres 9.6+?
I'm thinking that ideally the solution has a signature similar to:
generate_uid(size integer) returns text
Where size is customizable depending on your own tradeoffs for lowering the chance of collisions vs. reducing the string size for usability.
From what I can tell, it must use gen_random_bytes() instead of random() for true randomness, to reduce the chance that they can be guessed.
Thanks!
I know there's gen_random_uuid() for UUIDs, but I don't want to use them in this case. I'm looking for something that gives me IDs similar to what Stripe (or others) use, that look like: "id": "ch_19iRv22eZvKYlo2CAxkjuHxZ" that are as short as possible while still containing only alphanumeric characters.
This requirement is also why encode(gen_random_bytes(), 'hex') isn't quite right for this case, since it reduces the character set and thus forces me to increase the length of the strings to avoid collisions.
I'm currently doing this in the application layer, but I'm looking to move it into the database layer to reduce interdependencies. Here's what the Node.js code for doing it in the application layer might look like:
var crypto = require('crypto');
var set = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
function generate(length) {
var bytes = crypto.randomBytes(length);
var chars = [];
for (var i = 0; i < bytes.length; i++) {
chars.push(set[bytes[i] % set.length]);
}
return chars.join('');
}
Figured this out, here's a function that does it:
CREATE OR REPLACE FUNCTION generate_uid(size INT) RETURNS TEXT AS $$
DECLARE
characters TEXT := 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
bytes BYTEA := gen_random_bytes(size);
l INT := length(characters);
i INT := 0;
output TEXT := '';
BEGIN
WHILE i < size LOOP
output := output || substr(characters, get_byte(bytes, i) % l + 1, 1);
i := i + 1;
END LOOP;
RETURN output;
END;
$$ LANGUAGE plpgsql VOLATILE;
And then to run it simply do:
generate_uid(10)
-- '3Rls4DjWxJ'
Warning
When doing this you need to be sure that the length of the IDs you are creating is sufficient to avoid collisions over time as the number of objects you've created grows, which can be counter-intuitive because of the Birthday Paradox. So you will likely want a length greater (or much greater) than 10 for any reasonably commonly created object, I just used 10 as a simple example.
Usage
With the function defined, you can use it in a table definition, like so:
CREATE TABLE users (
id TEXT PRIMARY KEY DEFAULT generate_uid(10),
name TEXT NOT NULL,
...
);
And then when inserting data, like so:
INSERT INTO users (name) VALUES ('ian');
INSERT INTO users (name) VALUES ('victor');
SELECT * FROM users;
It will automatically generate the id values:
id | name | ...
-----------+--------+-----
owmCAx552Q | ian |
ZIofD6l3X9 | victor |
Usage with a Prefix
Or maybe you want to add a prefix for convenience when looking at a single ID in the logs or in your debugger (similar to how Stripe does it), like so:
CREATE TABLE users (
id TEXT PRIMARY KEY DEFAULT ('user_' || generate_uid(10)),
name TEXT NOT NULL,
...
);
INSERT INTO users (name) VALUES ('ian');
INSERT INTO users (name) VALUES ('victor');
SELECT * FROM users;
id | name | ...
---------------+--------+-----
user_wABNZRD5Zk | ian |
user_ISzGcTVj8f | victor |
I'm looking for something that gives me "shortcodes" (similar to what Youtube uses for video IDs) that are as short as possible while still containing only alphanumeric characters.
This is a fundamentally different question from what you first asked. What you want here then is to put a serial type on the table, and to use hashids.org code for PostgreSQL.
This returns 1:1 with the unique number (serial)
Never repeats or has a chance of collision.
Also base62 [a-zA-Z0-9]
Code looks like this,
SELECT id, hash_encode(foo.id)
FROM foo; -- Result: jNl for 1001
SELECT hash_decode('jNl') -- returns 1001
This module also supports salts.
Review,
26 characters in [a-z]
26 characters in [A-Z]
10 characters in [0-9]
62 characters in [a-zA-Z0-9] (base62)
The function substring(string [from int] [for int]) looks useful.
So it looks something like this. First we demonstrate that we can take the random-range and pull from it.
SELECT substring(
'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789',
1, -- 1 is 'a', 62 is '9'
1,
);
Now we need a range between 1 and 63
SELECT trunc(random()*62+1)::int+1
FROM generate_series(1,1e2) AS gs(x)
This gets us there.. Now we just have to join the two..
SELECT substring(
'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789',
trunc(random()*62)::int+1
1
)
FROM generate_series(1,1e2) AS gs(x);
Then we wrap it in an ARRAY constructor (because this is fast)
SELECT ARRAY(
SELECT substring(
'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789',
trunc(random()*62)::int+1,
1
)
FROM generate_series(1,1e2) AS gs(x)
);
And, we call array_to_string() to get a text.
SELECT array_to_string(
ARRAY(
SELECT substring(
'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789',
trunc(random()*62)::int+1,
1
)
FROM generate_series(1,1e2) AS gs(x)
)
, ''
);
From here we can even turn it into a function..
CREATE FUNCTION random_string(randomLength int)
RETURNS text AS $$
SELECT array_to_string(
ARRAY(
SELECT substring(
'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789',
trunc(random()*62)::int+1,
1
)
FROM generate_series(1,randomLength) AS gs(x)
)
, ''
)
$$ LANGUAGE SQL
RETURNS NULL ON NULL INPUT
VOLATILE LEAKPROOF;
and then
SELECT * FROM random_string(10);
Thanks to Evan Carroll answer, I took a look on hashids.org.
For Postgres you have to compile the extension or run some TSQL functions.
But for my needs, I created something simpler based on hashids ideas (short, unguessable, unique, custom alphabet, avoid curse words).
Shuffle alphabet:
CREATE OR REPLACE FUNCTION consistent_shuffle(alphabet TEXT, salt TEXT) RETURNS TEXT AS $$
DECLARE
SALT_LENGTH INT := length(salt);
integer INT = 0;
temp TEXT = '';
j INT = 0;
v INT := 0;
p INT := 0;
i INT := length(alphabet) - 1;
output TEXT := alphabet;
BEGIN
IF salt IS NULL OR length(LTRIM(RTRIM(salt))) = 0 THEN
RETURN alphabet;
END IF;
WHILE i > 0 LOOP
v := v % SALT_LENGTH;
integer := ASCII(substr(salt, v + 1, 1));
p := p + integer;
j := (integer + v + p) % i;
temp := substr(output, j + 1, 1);
output := substr(output, 1, j) || substr(output, i + 1, 1) || substr(output, j + 2);
output := substr(output, 1, i) || temp || substr(output, i + 2);
i := i - 1;
v := v + 1;
END LOOP;
RETURN output;
END;
$$ LANGUAGE plpgsql VOLATILE;
The main function:
CREATE OR REPLACE FUNCTION generate_uid(id INT, min_length INT, salt TEXT) RETURNS TEXT AS $$
DECLARE
clean_alphabet TEXT := 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890';
curse_chars TEXT := 'csfhuit';
curse TEXT := curse_chars || UPPER(curse_chars);
alphabet TEXT := regexp_replace(clean_alphabet, '[' || curse || ']', '', 'gi');
shuffle_alphabet TEXT := consistent_shuffle(alphabet, salt);
char_length INT := length(alphabet);
output TEXT := '';
BEGIN
WHILE id != 0 LOOP
output := output || substr(shuffle_alphabet, (id % char_length) + 1, 1);
id := trunc(id / char_length);
END LOOP;
curse := consistent_shuffle(curse, output || salt);
output := RPAD(output, min_length, curse);
RETURN output;
END;
$$ LANGUAGE plpgsql VOLATILE;
How-to use examples:
-- 3: min-length
select generate_uid(123, 3, 'salt'); -- output: "0mH"
-- or as default value in a table
CREATE SEQUENCE IF NOT EXISTS my_id_serial START 1;
CREATE TABLE collections (
id TEXT PRIMARY KEY DEFAULT generate_uid(CAST (nextval('my_id_serial') AS INTEGER), 3, 'salt')
);
insert into collections DEFAULT VALUES ;
This query generate required string. Just change second parasmeter of generate_series to choose length of random string.
SELECT
string_agg(c, '')
FROM (
SELECT
chr(r + CASE WHEN r > 25 + 9 THEN 97 - 26 - 9 WHEN r > 9 THEN 64 - 9 ELSE 48 END) AS c
FROM (
SELECT
i,
(random() * 60)::int AS r
FROM
generate_series(0, 62) AS i
) AS a
ORDER BY i
) AS A;
So I had my own use-case for something like this. I am not proposing a solution to the top question, but if you are looking for something similar like I am, then try this out.
My use-case was that I needed to create a random external UUID (as a primary key) with as few characters as possible. Thankfully, the scenario did not have a requirement that a large amount of these would ever be needed (probably in the thousands only). Therefore a simple solution was a combination of using generate_uid() and checking to make sure that the next sequence was not already used.
Here is how I put it together:
CREATE OR REPLACE FUNCTION generate_id (
in length INT
, in for_table text
, in for_column text
, OUT next_id TEXT
) AS
$$
DECLARE
id_is_used BOOLEAN;
loop_count INT := 0;
characters TEXT := 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
loop_length INT;
BEGIN
LOOP
next_id := '';
loop_length := 0;
WHILE loop_length < length LOOP
next_id := next_id || substr(characters, get_byte(gen_random_bytes(length), loop_length) % length(characters) + 1, 1);
loop_length := loop_length + 1;
END LOOP;
EXECUTE format('SELECT TRUE FROM %s WHERE %s = %s LIMIT 1', for_table, for_column, quote_literal(next_id)) into id_is_used;
EXIT WHEN id_is_used IS NULL;
loop_count := loop_count + 1;
IF loop_count > 100 THEN
RAISE EXCEPTION 'Too many loops. Might be reaching the practical limit for the given length.';
END IF;
END LOOP;
END
$$
LANGUAGE plpgsql
STABLE
;
here is an example table usage:
create table some_table (
id
TEXT
DEFAULT generate_id(6, 'some_table', 'id')
PRIMARY KEY
)
;
and a test to see how it breaks:
DO
$$
DECLARE
loop_count INT := 0;
BEGIN
-- WHILE LOOP
WHILE loop_count < 1000000
LOOP
INSERT INTO some_table VALUES (DEFAULT);
loop_count := loop_count + 1;
END LOOP;
END
$$ LANGUAGE plpgsql
;
I found this code snipped (Source):
CREATE PROCEDURE rec_fib(n INT, OUT out_fib INT)
BEGIN
DECLARE n_1 INT;
DECLARE n_2 INT;
IF (n=0) THEN
SET out_fib=0;
ELSEIF (n=1) then
SET out_fib=1;
ELSE
CALL rec_fib(n-1,n_1);
CALL rec_fib(n-2,n_2);
SET out_fib=(n_1 + n_2);
END IF;
END
This code works with MySQL. In how far do I have to modify it to run on DB2? I cannot seem to find a running minimal example of an recursive stored procedure for DB2.
This works for me: (I haven't done more than make it work, so alternative coding could also work.)
First, add these two lines:
DECLARE n_3 INT;
DECLARE n_4 INT;
Then modify this small section:
ELSE
set n_3 = n - 1;
set n_4 = n - 2;
CALL rec_fib(n_3,n_1);
CALL rec_fib(n_4,n_2);
That's all. Runs on IBM i 6.1 DB2 UDB.
The following code is from SQL tips for DB2, written by Serge Rielau
CREATE OR REPLACE FUNCTION Fib(n INTEGER) RETURNS DECIMAL(31, 0)
BEGIN
DECLARE res DECIMAL(31, 0);
CASE WHEN n = 0 THEN
SET res = 0;
WHEN n = 1 THEN
SET res = 1;
WHEN n > 1 THEN
BEGIN
DECLARE stmt STATEMENT;
PREPARE stmt FROM 'SET ? = Fib(? - 1) + Fib(? - 2)';
EXECUTE stmt INTO res USING n, n;
END;
ELSE
SIGNAL SQLSTATE '78000' SET MESSAGE_TEXT = 'Bad input';
END CASE;
RETURN res;
END;
/
For more information, please check the source page of this code: https://www.ibm.com/developerworks/community/blogs/SQLTips4DB2LUW/entry/recursive_sql_pl?lang=en
I am trying to create a script that will allow the user to select which CASE population to use from an ACCEPT when gathering student contact info.
PROMPT 'Select a popluation for emails'
PROMPT '1. Currently registered'
PROMPT '2. New Applicants'
PROMPT
ACCEPT cnt number PROMPT 'Selection: ';
...
CURSOR stu_lst IS
CASE &cnt
WHEN 1 THEN -- Current registered students.
select distinct SFRSTCA_PIDM pidm
from SFRSTCA
where SFRSTCA_TERM_CODE = '201403' and
SFRSTCA_LEVL_CODE = '01' and
SFRSTCA_RSTS_CODE = 'RE';
WHEN 2 THEN -- New applicants
select app_pidm pidm
from app
where app_term = 'Fall 2014';
ELSE
-- Incorrect selection.
DBMS_OUTPUT.PUT_LINE('Incorrect selection made.');
exit;
END;
END;
Assuming the two queries return the same data type, you could use a union with a filter that checks the variable in each part; something like:
DECLARE
CURSOR stu_lst IS
-- Current registered students.
select distinct SFRSTCA_PIDM pidm
from SFRSTCA
where &cnt = 1 and
SFRSTCA_TERM_CODE = '201403' and
SFRSTCA_LEVL_CODE = '01' and
SFRSTCA_RSTS_CODE = 'RE';
UNION ALL
-- New applicants
select app_pidm
from app
where &cnt = 2 and
app_term = 'Fall 2014';
invalid_argument EXCEPTION;
...
BEGIN
IF &cnt NOT IN (1, 2) THEN
RAISE invalid_argument;
END IF
FOR rec IN stu_lst LOOP
h_pidm := rec.pidm;
...
END LOOP;
EXCEPTION
WHEN invalid_argument THEN
dbms_output.put_line('Incorrect selection made.');
END;
/
You could also declare a cursor variable and open that with the appropriate query, inside a case statement within the main body of the block. This sticks with your explicit cursor syntax though.