MySQL calling a procedure with select statements from a trigger - “Not allowed to return a result set from a trigger”
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25-07-2021 - |
문제
Here's one for the SQL wizards. Similar questions have been asked before and I have some idea what the problem is but I'm having trouble rewriting the select statements inside my procedure to avoid returning a result set, and returning the global vars my trigger wants.
For a bit of background, what I'm trying to accomplish here is to use a group of triggers to call procedures which will calculate the percentile of a value relative to other rows in the table with the same gene_id, on insert or update of rows.
(using PMA delimiter is set to |)
The procedure to calculate the percentile value works fine
DROP PROCEDURE IF EXISTS gecg_relative_expr_compendium |
CREATE PROCEDURE gecg_relative_expr_compendium( IN in_gene_id varchar(24), IN in_fpkm double, OUT percentile float(4,2) )
BEGIN
SET @row := 0;
SELECT fpkm, ( (rank / @row) *100 ) AS percentile
FROM (
SELECT fpkm, @row := @row +1 AS rank, gene_id
FROM gene_expression_cufflinks_gene
WHERE gene_id = in_gene_id
ORDER BY fpkm ASC
) AS p
WHERE fpkm = in_fpkm;
END |
I can call it like so:
CALL gecg_relative_expr_compendium('ENSG00000251948', 19367800, @percentile)
Returns:
fpkm percentile
19367800 100.0000
And my trigger:
DROP TRIGGER IF EXISTS insert_gecg_relative_expr |
CREATE TRIGGER insert_gecg_relative_expr
BEFORE INSERT ON `gene_expression_cufflinks_gene` FOR EACH ROW
BEGIN
CALL gecg_relative_expr_compendium(NEW.gene_id, NEW.fpkm, NEW.fpkm_percentile_compendium) ;
END |
When I insert a row triggering the trigger, it fails (irrelevant columns trimmed for clarity)
INSERT INTO `mctp`.`gene_expression_cufflinks_gene` (
`gene_id` ,
`fpkm`,
`fpkm_percentile_compendium` ,
`fpkm_percentile_origin_tissue` ,
`fpkm_percentile_collection_tissue` ,
`fpkm_percentile_sample_cancer`
)
VALUES ('ENSG00000239906','555', NULL , NULL , NULL , NULL , NULL , NULL)
Eventually I want my trigger to insert the calculated NEW percentile values into the row being inserted, such as NEW.fkpm_percentile_compendium. Precalculating these percentile values is going to be necessary for performance reasons because this table will be > 500m rows, and eventually other percentile values will have to be computed based on relations, resulting in excessive joins.
I have a vague idea that the solution should involve SELECT INTO variables instead of a plain select statement, but this breaks my procedure.
DROP PROCEDURE IF EXISTS gecg_relative_expr_compendium |
CREATE PROCEDURE gecg_relative_expr_compendium( IN in_gene_id varchar(24), IN in_fpkm double, OUT percentile float(4,2) )
BEGIN
SET @row := 0;
SELECT fpkm, ( (rank / @row) *100 ) AS percentile INTO fpkm, percentile
FROM (
SELECT fpkm, @row := @row +1 AS rank, gene_id
FROM gene_expression_cufflinks_gene
WHERE gene_id = in_gene_id
ORDER BY fpkm ASC
) AS p
WHERE fpkm = in_fpkm;
END |
gives me:
#1327 - Undeclared variable: fpkm
So my questions are
1> How can I access the new vars I've selected INTO from within the same procedure?
2> how can I do this in such a way as to return the vars to the trigger without returning a result set?
Thanks so much for your help.
UPDATE >> Here are the working procedure and trigger:
DROP PROCEDURE IF EXISTS gecg_relative_expr_compendium |
CREATE PROCEDURE gecg_relative_expr_compendium( IN in_gene_id varchar(24), IN in_fpkm double, OUT out_fpkm double, OUT out_percentile float(5,2) )
BEGIN
SET @row := 0;
SELECT fpkm, ( (rank / @row) *100 ) AS percentile
FROM (
SELECT fpkm, @row := @row +1 AS rank, gene_id
FROM gene_expression_cufflinks_gene
WHERE gene_id = in_gene_id
ORDER BY fpkm ASC
) AS p
WHERE fpkm = in_fpkm
LIMIT 1
INTO out_fpkm, out_percentile;
END |
DROP TRIGGER IF EXISTS insert_gecg_relative_expr |
CREATE TRIGGER insert_gecg_relative_expr
BEFORE INSERT ON `gene_expression_cufflinks_gene` FOR EACH ROW
BEGIN
CALL gecg_relative_expr_compendium(NEW.gene_id, NEW.fpkm, @f, @p);
SET NEW.fpkm_percentile_compendium = @p;
END
|
The trigger runs the percentile calculation on a row as it gets inserted. Now on to the next task, to run that procedure on all the other rows that match this gene_id. guhhh.
xoxoxox
해결책
Two things come to mind:
1) this is strange syntax:
SELECT fpkm, ( (rank / @row) *100 ) AS percentile INTO fpkm, percentile
You can't use 'fpkm' until after this select statement.
2) its a bit hokey but one way to 'return' values from a procedure is to put them into a temp table. Then select them out from the calling process.
다른 팁
SELECT fpkm, ( (rank / @row) *100 ) AS percentile INTO fpkm, percentile
^^^^
there's your undeclared var. probably should be in_fpkm
or other name.