SnowConvert AI - Messages généraux d’examen des performances¶

SSC-PRF-0001¶

Cette instruction utilise des opérations de récupération en masse de curseurs.

Description¶

Cet avertissement indique que l’instruction utilise des opérations d’extraction en bloc du curseur. Ces opérations vous permettent de récupérer plusieurs lignes de données d’un curseur en même temps, au lieu d’une ligne à la fois. L’utilisation d’opérations en bloc améliore les performances en réduisant le nombre de communications nécessaires entre le client et le serveur.

Ce modèle peut devenir complexe s’il n’est pas mis en œuvre correctement. Par exemple, récupérer un trop grand nombre de lignes lors d’une seule opération de récupération peut entraîner une consommation excessive de mémoire. Il est essentiel de maintenir un équilibre entre le nombre de lignes extraites et les ressources mémoire disponibles.

Exemple de code¶

Oracle¶
Entrée¶
 CREATE OR REPLACE PROCEDURE oracle_cursor_fetch_bulk AS
--cursor and variable declarations
BEGIN
    OPEN c1;
    FETCH c1 BULK COLLECT INTO col1;
    CLOSE c1;
END;

Sortie¶
 CREATE OR REPLACE PROCEDURE oracle_cursor_fetch_bulk ()
RETURNS VARCHAR
LANGUAGE SQL
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},{"attributes":{"component":"oracle"}}'
EXECUTE AS CALLER
AS
--cursor and variable declarations
$$
    BEGIN
        OPEN c1;
        --** SSC-PRF-0001 - THIS STATEMENT HAS USAGES OF CURSOR FETCH BULK OPERATIONS **
        c1 := (
            CALL FETCH_BULK_COLLECTION_RECORDS_UDF(:c1)
        );
        col1 := :c1:RESULT;
        CLOSE c1;
    END;
$$;

Meilleures pratiques¶

Pour une assistance supplémentaire, veuillez nous contacter à l’adresse suivante : snowconvert-support@snowflake.com

SSC-PRF-0002¶

Les colonnes insensibles à la casse peuvent réduire les performances des requêtes.

Description¶

L’utilisation du classement dans Snowflake peut avoir un impact sur les performances des requêtes, en particulier dans les clauses WHERE. Pour en savoir plus sur la manière dont le classement affecte les performances, veuillez vous référer à la section Implications de l’utilisation du classement sur les performances.

Un avertissement a été généré pour indiquer qu’une colonne a été créée avec un classement insensible à la casse. L’utilisation de cette colonne dans les requêtes peut ralentir les performances.

Exemples de code :¶

Sortie¶

 CREATE TABLE exampleTable
(
    col1 CHAR(10),
    col2 CHAR(20) COLLATE 'en-ci' /*** SSC-PRF-0002 - CASE INSENSITIVE COLUMNS CAN DECREASE THE PERFORMANCE OF QUERIES ***/
)
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},{"attributes":{"component":"teradata"}}'
;

Oracle¶

Entrée¶

 CREATE TABLE exampleTable (
    col1 VARCHAR(50) COLLATE BINARY_CI,
    col2 VARCHAR(50) COLLATE BINARY_CS
);

Sortie¶

 CREATE OR REPLACE TABLE exampleTable (
       col1 VARCHAR(50) COLLATE BINARY_CI /*** SSC-PRF-0002 - CASE INSENSITIVE COLUMNS CAN DECREASE THE PERFORMANCE OF QUERIES ***/,
       col2 VARCHAR(50) COLLATE BINARY_CS
   )
   COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},{"attributes":{"component":"oracle"}}'
   ;

Microsoft SQL Server¶

Entrée¶

 CREATE TABLE exampleTable (
    col1 VARCHAR(50) COLLATE Latin1_General_CI_AS,
    col2 VARCHAR(50) COLLATE Latin1_General_CS_AS
);

Sortie¶

 CREATE OR REPLACE TABLE exampleTable (
    col1 VARCHAR(50) COLLATE 'EN-CI-AS' /*** SSC-PRF-0002 - CASE INSENSITIVE COLUMNS CAN DECREASE THE PERFORMANCE OF QUERIES ***/,
    col2 VARCHAR(50) COLLATE 'EN-CS-AS'
)
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},"attributes":{"component":"transact"}}'
;

Meilleures pratiques¶

Si les performances de votre application sont considérablement affectées par le classement insensible à la casse, envisagez de réécrire votre code pour ne pas l’utiliser. Toutefois, si l’impact sur les performances est acceptable, vous pouvez ignorer cet avertissement.
Pour toute assistance supplémentaire, contactez-nous à l’adresse suivante : snowconvert-support@snowflake.com

SSC-PRF-0003¶

La récupération dans une boucle est considérée comme un modèle complexe, susceptible de dégrader les performances de Snowflake.

Gravité¶

Faible

Description¶

Cet avertissement apparaît lorsqu’une instruction FETCH est détectée dans une boucle. L’instruction FETCH récupère et traite une à une les lignes d’un jeu de résultats.

Le traitement de grands ensembles de données à l’aide de curseurs dans des boucles peut devenir complexe, en particulier lorsque :

Des jointures de tables multiples sont impliquées
Des calculs complexes sont exigés
Un grand nombre de lignes doit être traité

Ce modèle peut entraîner des problèmes de performance et peut être difficile à maintenir au fur et à mesure que le volume de données augmente.

Exemple de code¶

Teradata¶

Entrée¶

 REPLACE PROCEDURE teradata_fetch_inside_loop()
DYNAMIC RESULT SETS 1
BEGIN
    DECLARE col_name VARCHAR(200);
    DECLARE col_int INTEGER DEFAULT 0;
    DECLARE cursor_var CURSOR FOR SELECT some_column FROM tabla1;
    WHILE (col_int <> 0) DO		
        FETCH cursor_var INTO col_name;
        SET col_int = col_int + 1;
    END WHILE;
END;

Sortie¶

 --** SSC-FDM-0007 - MISSING DEPENDENT OBJECT "tabla1" **
CREATE OR REPLACE PROCEDURE teradata_fetch_inside_loop ()
RETURNS VARCHAR
LANGUAGE SQL
COMMENT = '{ "origin": "sf_sc", "name": "snowconvert", "version": {  "major": 0,  "minor": 0,  "patch": "0" }, "attributes": {  "component": "teradata",  "convertedOn": "07/02/2025",  "domain": "no-domain-provided" }}'
EXECUTE AS CALLER
AS
$$
    DECLARE
        col_name VARCHAR(200);
        col_int INTEGER DEFAULT 0;
    BEGIN
         
         
        LET cursor_var CURSOR
        FOR
            SELECT
                some_column FROM
                tabla1;
                WHILE (:col_int <> 0) LOOP
            --** SSC-PRF-0003 - FETCH INSIDE A LOOP IS CONSIDERED A COMPLEX PATTERN, THIS COULD DEGRADE SNOWFLAKE PERFORMANCE. **
                    FETCH cursor_var INTO col_name;
            col_int := col_int + 1;
                END LOOP;
    END;
$$;

Oracle¶

Entrée¶

 CREATE PROCEDURE oracle_fetch_inside_loop
IS
  var1 table1.column1%TYPE;
  CURSOR cursor1 IS SELECT COLUMN_NAME FROM table1; 
BEGIN
  WHILE true LOOP
    FETCH cursor1 INTO var1;
    EXIT WHEN cursor1%NOTFOUND;
  END LOOP;  
END;

Sortie¶

 CREATE OR REPLACE PROCEDURE oracle_fetch_inside_loop ()
RETURNS VARCHAR
LANGUAGE SQL
COMMENT = '{ "origin": "sf_sc", "name": "snowconvert", "version": {  "major": 0,  "minor": 0,  "patch": "0" }, "attributes": {  "component": "oracle",  "convertedOn": "07/02/2025",  "domain": "no-domain-provided" }}'
EXECUTE AS CALLER
AS
$$
  DECLARE
    var1 VARIANT !!!RESOLVE EWI!!! /*** SSC-EWI-OR0129 - TYPE ATTRIBUTE 'table1.column1%TYPE' COULD NOT BE RESOLVED, SO IT WAS TRANSFORMED TO VARIANT ***/!!!;
    --** SSC-PRF-0009 - PERFORMANCE REVIEW - CURSOR USAGE **
    cursor1 CURSOR
    FOR
      SELECT COLUMN_NAME FROM
        table1;
  BEGIN
    WHILE (true)
                 --** SSC-PRF-0008 - PERFORMANCE REVIEW - LOOP USAGE **
                 LOOP
      --** SSC-PRF-0003 - FETCH INSIDE A LOOP IS CONSIDERED A COMPLEX PATTERN, THIS COULD DEGRADE SNOWFLAKE PERFORMANCE. **
         FETCH cursor1 INTO
        :var1;
         IF (var1 IS NULL) THEN
        EXIT;
         END IF;
       END LOOP;
  END;
$$;

SQL Server¶

Entrée¶

 CREATE OR ALTER PROCEDURE transact_fetch_inside_loop
AS
BEGIN
    DECLARE cursor1 CURSOR
        FOR SELECT col1 FROM my_table;
    WHILE 1=0
    BEGIN
       FETCH NEXT FROM @cursor1 INTO @variable1;
    END
END;

Sortie¶

 CREATE OR REPLACE PROCEDURE transact_fetch_inside_loop ()
RETURNS VARCHAR
LANGUAGE SQL
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},{"attributes":{"component":"transact"}}'
EXECUTE AS CALLER
AS
$$
    DECLARE
        --** SSC-FDM-TS0013 - SNOWFLAKE SCRIPTING CURSOR ROWS ARE NOT MODIFIABLE **
        cursor1 CURSOR
        FOR
            SELECT
                col1
            FROM
                my_table;
    BEGIN
         
        WHILE (1=0) LOOP
            --** SSC-PRF-0003 - FETCH INSIDE A LOOP IS CONSIDERED A COMPLEX PATTERN, THIS COULD DEGRADE SNOWFLAKE PERFORMANCE. **
            FETCH
                CURSOR1
                INTO
                :VARIABLE1;
        END LOOP;
    END;
$$;

Meilleures pratiques¶

Pour améliorer les performances et éviter les modèles complexes, utilisez des opérations basées sur des ensembles plutôt que des boucles. Remplacez le traitement ligne par ligne par des instructions SQL (SELECT, UPDATE, DELETE) qui opèrent simultanément sur plusieurs lignes à l’aide de clauses WHERE. Cette approche est plus efficace et plus facile à maintenir.

Oracle¶

 CREATE OR REPLACE PROCEDURE cursor_fetch_inside_loop 
AS
  record_employee employees%rowtype;
  CURSOR emp_cursor IS SELECT * FROM employees;
BEGIN
  OPEN emp_cursor;
  LOOP
    FETCH emp_cursor INTO record_employee;
    EXIT WHEN emp_cursor%notfound;
    INSERT INTO new_employees VALUES (record_employee.first_name, record_employee.last_name);
  END LOOP;
  CLOSE emp_cursor;
END;

Snowflake¶

 CREATE OR REPLACE PROCEDURE cursor_fetch_inside_loop ()
RETURNS VARCHAR
LANGUAGE SQL
COMMENT = '{ "origin": "sf_sc", "name": "snowconvert", "version": {  "major": 0,  "minor": 0,  "patch": "0" }, "attributes": {  "component": "oracle",  "convertedOn": "07/02/2025",  "domain": "no-domain-provided" }}'
EXECUTE AS CALLER
AS
$$
  DECLARE
    record_employee OBJECT !!!RESOLVE EWI!!! /*** SSC-EWI-0036 - ROWTYPE DATA TYPE CONVERTED TO OBJECT ***/!!! := OBJECT_CONSTRUCT();
    --** SSC-PRF-0009 - PERFORMANCE REVIEW - CURSOR USAGE **
    emp_cursor CURSOR
    FOR
      SELECT
        OBJECT_CONSTRUCT( *) sc_cursor_record FROM
        employees;
  BEGIN
    OPEN emp_cursor;
    --** SSC-PRF-0008 - PERFORMANCE REVIEW - LOOP USAGE **
    LOOP
      --** SSC-PRF-0003 - FETCH INSIDE A LOOP IS CONSIDERED A COMPLEX PATTERN, THIS COULD DEGRADE SNOWFLAKE PERFORMANCE. **
      FETCH emp_cursor INTO
        :record_employee;
      IF (record_employee IS NULL) THEN
        EXIT;
      END IF;
      INSERT INTO new_employees
      SELECT
        :record_employee:FIRST_NAME,
        :record_employee:LAST_NAME;
    END LOOP;
  CLOSE emp_cursor;
  END;
$$;

Les opérations basées sur les ensembles peuvent être utilisées pour traiter les données plus efficacement.

 CREATE OR REPLACE PROCEDURE cursor_fetch_inside_loop AS
BEGIN
  INSERT INTO new_employees (first_name, last_name)
  SELECT first_name, last_name FROM employees;
END;

Les opérations basées sur les ensembles peuvent être utilisées pour traiter les données plus efficacement.

 CREATE OR REPLACE PROCEDURE cursor_fetch_inside_loop ()
RETURNS VARCHAR
LANGUAGE SQL
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},{"attributes":{"component":"oracle"}}'
EXECUTE AS CALLER
AS
$$
  BEGIN
    INSERT INTO new_employees(first_name, last_name)
    SELECT first_name, last_name FROM
      employees;
  END;
$$;

Meilleures pratiques¶

Pour une assistance supplémentaire, veuillez nous contacter à l’adresse suivante : snowconvert-support@snowflake.com

SSC-PRF-0004¶

Cette instruction utilise un curseur For Loop.

Gravité¶

Aucun(e)

Description¶

Cet avertissement indique que l’instruction contient un curseur For loops. Une boucle de curseur est une structure de programmation qui traite les résultats d’une requête une ligne à la fois, ce qui vous permet de travailler avec des enregistrements individuels d’un jeu de résultats.

Cet avertissement permet d’identifier les problèmes de performance potentiels dans les boucles FOR du curseur. Des problèmes de performance peuvent survenir dans les cas suivants :

L’instruction SELECT au sein du curseur renvoie un grand ensemble de données
La boucle contient des opérations complexes
La boucle contient des boucles imbriquées

Si SnowConvert AI peut détecter ces modèles, vous devez examiner et optimiser le code pour garantir une exécution efficace.

Exemple de code¶

Teradata¶

Entrée¶

 REPLACE PROCEDURE teradata_cursor_for_loop()    
BEGIN
    FOR fUsgClass AS cUsgClass CURSOR FOR
        (SELECT col1
        FROM sample_table)
    DO
        SET var1 = fUsgClass.col1;
    END FOR;
END;

Sortie¶

 --** SSC-FDM-0007 - MISSING DEPENDENT OBJECT "sample_table" **
CREATE OR REPLACE PROCEDURE teradata_cursor_for_loop ()
RETURNS VARCHAR
LANGUAGE SQL
COMMENT = '{ "origin": "sf_sc", "name": "snowconvert", "version": {  "major": 0,  "minor": 0,  "patch": "0" }, "attributes": {  "component": "teradata",  "convertedOn": "07/16/2025",  "domain": "no-domain-provided" }}'
EXECUTE AS CALLER
AS
$$
    DECLARE
        !!!RESOLVE EWI!!! /*** SSC-EWI-0110 - TRANSFORMATION NOT PERFORMED DUE TO MISSING DEPENDENCIES ***/!!!
        temp_fUsgClass_col1;
    BEGIN
        LET cUsgClass CURSOR
        FOR
            SELECT
                col1
                   FROM
                sample_table;
        --** SSC-PRF-0004 - THIS STATEMENT HAS USAGES OF CURSOR FOR LOOP **
        FOR fUsgClass IN cUsgClass DO
            temp_fUsgClass_col1 := fUsgClass.col1;
            var1 := :temp_fUsgClass_col1;
        END FOR;
    END;
$$;

Oracle¶

Entrée¶

 CREATE OR REPLACE PROCEDURE oracle_cursor_for_loop AS
BEGIN
    FOR r1 IN (SELECT col1 FROM sample_table) LOOP
        NULL;
    END LOOP;
END;

Sortie¶

 CREATE OR REPLACE PROCEDURE oracle_cursor_for_loop ()
RETURNS VARCHAR
LANGUAGE SQL
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},{"attributes":{"component":"oracle"}}'
EXECUTE AS CALLER
AS
$$
    BEGIN
        LET temporary_for_cursor_0 CURSOR
        FOR
            (SELECT col1 FROM
                    sample_table
            );
        --** SSC-PRF-0004 - THIS STATEMENT HAS USAGES OF CURSOR FOR LOOP **
        FOR r1 IN temporary_for_cursor_0 DO
            NULL;
        END FOR;
    END;
$$;

Meilleures pratiques¶

Pour une assistance supplémentaire, veuillez nous contacter à l’adresse suivante : snowconvert-support@snowflake.com

SSC-PRF-0005¶

L’instruction ci-dessous utilise des curseurs imbriqués.

Note

Pour une meilleure lisibilité, nous avons simplifié certaines sections du code dans cet exemple.

Gravité¶

Aucun(e)

Description¶

Cet avertissement indique que l’instruction contient des curseurs imbriqués. Un curseur est une fonction de base de données qui vous permet de traiter les lignes d’un résultat de requête une par une. On parle de curseurs imbriqués lorsque vous utilisez un curseur à l’intérieur de la boucle d’un autre curseur, ce qui peut avoir un impact sur les performances et doit être utilisé avec prudence.

Les curseurs imbriqués peuvent ralentir considérablement les performances de votre code, en particulier lorsque vous travaillez avec de grandes quantités de données. En effet, à chaque opération, le curseur doit communiquer avec le serveur de la base de données, ce qui entraîne des frais généraux et des retards supplémentaires.

Exemples de code :¶

SQL Server¶

Entrée¶

 CREATE OR ALTER PROCEDURE procedureSample
AS
BEGIN
  DECLARE
    @outer_category_id INT,
    @outer_category_name NVARCHAR(50),
    @inner_product_name NVARCHAR(50);

  -- Define the outer cursor
  DECLARE outer_cursor CURSOR FOR 
    SELECT category_id, category_name FROM categories;

  -- Open the outer cursor
  OPEN @outer_cursor;

  -- Fetch the first row from the outer cursor
  FETCH NEXT FROM outer_cursor INTO @outer_category_id, @outer_category_name;

  -- Start the outer loop
  WHILE @@FETCH_STATUS = 0
  BEGIN

    PRINT 'Category: ' + @outer_category_name;
	
    -- Define the inner cursor
    DECLARE inner_cursor CURSOR FOR
      SELECT product_name FROM products WHERE category_id = @outer_category_id;
    
    -- Open the inner cursor
    OPEN inner_cursor;
	FETCH NEXT FROM inner_cursor INTO @inner_product_name;

    WHILE @@FETCH_STATUS = 0
    BEGIN
      PRINT 'Product: ' + @inner_product_name + ' Category: ' + CAST(@outer_category_id AS NVARCHAR(10));

      -- Fetch the next row from the inner cursor
      FETCH NEXT FROM inner_cursor INTO @inner_product_name;
    END;

    -- Close the inner cursor
    CLOSE inner_cursor;
    DEALLOCATE inner_cursor;

    -- Fetch the next row from the outer cursor
    FETCH NEXT FROM outer_cursor INTO @outer_category_id, @outer_category_name;
  END;

  -- Close the outer cursor
  CLOSE outer_cursor;
  DEALLOCATE outer_cursor;
  
END;

Sortie¶

 CREATE OR REPLACE PROCEDURE procedureSample ()
RETURNS VARCHAR
LANGUAGE SQL
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},"attributes":{"component":"transact"}}'
EXECUTE AS CALLER
AS
$$
	DECLARE
		OUTER_CATEGORY_ID INT;
		OUTER_CATEGORY_NAME VARCHAR(50);
		INNER_PRODUCT_NAME VARCHAR(50);

		-- Define the outer cursor
		--** SSC-FDM-TS0013 - SNOWFLAKE SCRIPTING CURSOR ROWS ARE NOT MODIFIABLE **
		outer_cursor CURSOR
		FOR
			SELECT
				category_id,
				category_name
			FROM
				categories;

		-- Define the inner cursor
		--** SSC-FDM-TS0013 - SNOWFLAKE SCRIPTING CURSOR ROWS ARE NOT MODIFIABLE **
		inner_cursor CURSOR
		FOR
			SELECT
				product_name
			FROM
				products
			WHERE
				category_id = :OUTER_CATEGORY_ID;
	BEGIN
		 
		 

		-- Open the outer cursor
		--** SSC-PRF-0005 - THE STATEMENT BELOW HAS USAGES OF NESTED CURSORS. **
		OPEN OUTER_CURSOR;
  -- Fetch the first row from the outer cursor
		FETCH
			outer_cursor
			INTO
			:OUTER_CATEGORY_ID,
			:OUTER_CATEGORY_NAME;

			-- Start the outer loop

			  -- Define the inner cursor
			WHILE (:FETCH_STATUS = 0) LOOP
			!!!RESOLVE EWI!!! /*** SSC-EWI-0073 - PENDING FUNCTIONAL EQUIVALENCE REVIEW FOR 'PRINT' NODE ***/!!!

			  PRINT 'Category: ' + @outer_category_name;
			 

			-- Open the inner cursor
			OPEN inner_cursor;
			--** SSC-PRF-0003 - FETCH INSIDE A LOOP IS CONSIDERED A COMPLEX PATTERN, THIS COULD DEGRADE SNOWFLAKE PERFORMANCE. **
			FETCH
				inner_cursor
			INTO
				:INNER_PRODUCT_NAME;
			WHILE (:FETCH_STATUS = 0) LOOP
				!!!RESOLVE EWI!!! /*** SSC-EWI-0073 - PENDING FUNCTIONAL EQUIVALENCE REVIEW FOR 'PRINT' NODE ***/!!!
				PRINT 'Product: ' + @inner_product_name + ' Category: ' + CAST(@outer_category_id AS NVARCHAR(10));
				-- Fetch the next row from the inner cursor
				--** SSC-PRF-0003 - FETCH INSIDE A LOOP IS CONSIDERED A COMPLEX PATTERN, THIS COULD DEGRADE SNOWFLAKE PERFORMANCE. **
				FETCH
					inner_cursor
				INTO
					:INNER_PRODUCT_NAME;
			END LOOP;
			-- Close the inner cursor
			CLOSE inner_cursor;
			!!!RESOLVE EWI!!! /*** SSC-EWI-0058 - FUNCTIONALITY FOR 'DEALLOCATE' IS NOT CURRENTLY SUPPORTED BY SNOWFLAKE SCRIPTING ***/!!!
			  DEALLOCATE inner_cursor;
			-- Fetch the next row from the outer cursor
			--** SSC-PRF-0003 - FETCH INSIDE A LOOP IS CONSIDERED A COMPLEX PATTERN, THIS COULD DEGRADE SNOWFLAKE PERFORMANCE. **
			FETCH
				outer_cursor
			INTO
				:OUTER_CATEGORY_ID,
				:OUTER_CATEGORY_NAME;
			END LOOP;
  -- Close the outer cursor
			CLOSE outer_cursor;
			!!!RESOLVE EWI!!! /*** SSC-EWI-0058 - FUNCTIONALITY FOR 'DEALLOCATE' IS NOT CURRENTLY SUPPORTED BY SNOWFLAKE SCRIPTING ***/!!!
			DEALLOCATE outer_cursor;
	END;
$$;

Oracle¶

Curseur explicite¶

Entrée¶

 CREATE OR REPLACE PROCEDURE procedureSample AS
BEGIN
DECLARE
  CURSOR outer_cursor IS
    SELECT category_id, category_name FROM categories;

  CURSOR inner_cursor (p_category_id NUMBER) IS
    SELECT product_name FROM products WHERE category_id = p_category_id;

  outer_category_id categories.category_id%TYPE;
  outer_category_name categories.category_name%TYPE;
  inner_product_name products.product_name%TYPE;
BEGIN

  OPEN outer_cursor;
  FETCH outer_cursor INTO outer_category_id, outer_category_name;

  LOOP
    EXIT WHEN outer_cursor%NOTFOUND;
    DBMS_OUTPUT.PUT_LINE('Category: ' || outer_category_name);

    OPEN inner_cursor(outer_category_id);
    LOOP
        FETCH inner_cursor INTO inner_product_name;
        EXIT WHEN inner_cursor%NOTFOUND;
        DBMS_OUTPUT.PUT_LINE('Product: ' || inner_product_name || ' Category: ' || outer_category_id);
    END LOOP;
    CLOSE inner_cursor;

    FETCH outer_cursor INTO outer_category_id, outer_category_name;
  END LOOP;

  CLOSE outer_cursor;
END;
END;

Sortie¶

 CREATE OR REPLACE PROCEDURE procedureSample ()
RETURNS VARCHAR
LANGUAGE SQL
COMMENT = '{ "origin": "sf_sc", "name": "snowconvert", "version": {  "major": 0,  "minor": 0,  "patch": "0" }, "attributes": {  "component": "oracle",  "convertedOn": "07/02/2025",  "domain": "no-domain-provided" }}'
EXECUTE AS CALLER
AS
$$
  BEGIN
    DECLARE
      --** SSC-PRF-0009 - PERFORMANCE REVIEW - CURSOR USAGE **
      outer_cursor CURSOR
      FOR
        SELECT category_id, category_name FROM
          categories;
      --** SSC-PRF-0009 - PERFORMANCE REVIEW - CURSOR USAGE **
      inner_cursor CURSOR
      FOR
        SELECT product_name FROM
          products
        WHERE category_id = ?;
      outer_category_id VARIANT !!!RESOLVE EWI!!! /*** SSC-EWI-OR0129 - TYPE ATTRIBUTE 'categories.category_id%TYPE' COULD NOT BE RESOLVED, SO IT WAS TRANSFORMED TO VARIANT ***/!!!;
      outer_category_name VARIANT !!!RESOLVE EWI!!! /*** SSC-EWI-OR0129 - TYPE ATTRIBUTE 'categories.category_name%TYPE' COULD NOT BE RESOLVED, SO IT WAS TRANSFORMED TO VARIANT ***/!!!;
      inner_product_name VARIANT !!!RESOLVE EWI!!! /*** SSC-EWI-OR0129 - TYPE ATTRIBUTE 'products.PRODUCT_NAME%TYPE' COULD NOT BE RESOLVED, SO IT WAS TRANSFORMED TO VARIANT ***/!!!;
      call_results VARIANT;
    BEGIN
      --** SSC-PRF-0005 - THE STATEMENT BELOW HAS USAGES OF NESTED CURSORS. **
      OPEN outer_cursor USING ('DEFAULT VALUE NOT FOUND');
      FETCH outer_cursor INTO
        :outer_category_id,
        :outer_category_name;
      --** SSC-PRF-0008 - PERFORMANCE REVIEW - LOOP USAGE **
      LOOP
        IF (outer_category_id IS NULL) THEN
          EXIT;
        END IF;
        --** SSC-FDM-OR0035 - CHECK UDF IMPLEMENTATION FOR DBMS_OUTPUT.PUT_LINE_UDF. **
        call_results := (
          CALL DBMS_OUTPUT.PUT_LINE_UDF('Category: ' || NVL(:outer_category_name :: STRING, ''))
        );
        OPEN inner_cursor USING (:outer_category_id);
        --** SSC-PRF-0008 - PERFORMANCE REVIEW - LOOP USAGE **
        LOOP
          --** SSC-PRF-0003 - FETCH INSIDE A LOOP IS CONSIDERED A COMPLEX PATTERN, THIS COULD DEGRADE SNOWFLAKE PERFORMANCE. **
            FETCH inner_cursor INTO
            :inner_product_name;
          IF (inner_product_name IS NULL) THEN
            EXIT;
          END IF;
          --** SSC-FDM-OR0035 - CHECK UDF IMPLEMENTATION FOR DBMS_OUTPUT.PUT_LINE_UDF. **
          call_results := (
            CALL DBMS_OUTPUT.PUT_LINE_UDF('Product: ' || NVL(:inner_product_name :: STRING, '') || ' Category: ' || NVL(:outer_category_id :: STRING, ''))
          );
        END LOOP;
        CLOSE inner_cursor;
        --** SSC-PRF-0003 - FETCH INSIDE A LOOP IS CONSIDERED A COMPLEX PATTERN, THIS COULD DEGRADE SNOWFLAKE PERFORMANCE. **
        FETCH outer_cursor INTO
          :outer_category_id,
          :outer_category_name;
      END LOOP;
      CLOSE outer_cursor;
      RETURN call_results;
    END;
  END;
$$;

Curseur implicite¶

Entrée¶

 CREATE OR REPLACE PROCEDURE procedureSample AS
BEGIN
DECLARE
   inner_category_id categories.category_name%TYPE;
   inner_product_name products.product_name%TYPE;
   inner_cursor SYS_REFCURSOR;
BEGIN
   FOR outer_cursor IN (SELECT category_id, category_name FROM categories)
   LOOP
      OPEN inner_cursor
       FOR SELECT product_name, category_id FROM products WHERE category_id = outer_cursor.category_id;
      LOOP
         FETCH inner_cursor INTO inner_product_name, inner_category_id;
         EXIT WHEN inner_cursor%NOTFOUND;
         dbms_output.put_line( 'Category id: '|| outer_cursor.category_id);
         dbms_output.put_line('Product name: ' || inner_product_name);
      END LOOP;
      CLOSE inner_cursor;
   END LOOP;
END;
END;

Sortie¶

 CREATE OR REPLACE PROCEDURE procedureSample ()
RETURNS VARCHAR
LANGUAGE SQL
COMMENT = '{ "origin": "sf_sc", "name": "snowconvert", "version": {  "major": 0,  "minor": 0,  "patch": "0" }, "attributes": {  "component": "oracle",  "convertedOn": "07/02/2025",  "domain": "no-domain-provided" }}'
EXECUTE AS CALLER
AS
$$
   BEGIN
      DECLARE
         inner_category_id VARIANT !!!RESOLVE EWI!!! /*** SSC-EWI-OR0129 - TYPE ATTRIBUTE 'categories.category_name%TYPE' COULD NOT BE RESOLVED, SO IT WAS TRANSFORMED TO VARIANT ***/!!!;
         inner_product_name VARIANT !!!RESOLVE EWI!!! /*** SSC-EWI-OR0129 - TYPE ATTRIBUTE 'products.product_name%TYPE' COULD NOT BE RESOLVED, SO IT WAS TRANSFORMED TO VARIANT ***/!!!;
         inner_cursor_res RESULTSET;
         call_results VARIANT;
      BEGIN
         LET temporary_for_cursor_0 CURSOR
         FOR
            (SELECT category_id, category_name FROM
                  categories
            );
         --** SSC-PRF-0004 - THIS STATEMENT HAS USAGES OF CURSOR FOR LOOP **
         --** SSC-PRF-0005 - THE STATEMENT BELOW HAS USAGES OF NESTED CURSORS. **
         FOR outer_cursor IN temporary_for_cursor_0 DO
            LET inner_cursor CURSOR
            FOR
               SELECT product_name, category_id FROM
                  products
               WHERE category_id = outer_cursor.category_id;
            OPEN inner_cursor;
            --** SSC-PRF-0008 - PERFORMANCE REVIEW - LOOP USAGE **
                 LOOP
               --** SSC-PRF-0003 - FETCH INSIDE A LOOP IS CONSIDERED A COMPLEX PATTERN, THIS COULD DEGRADE SNOWFLAKE PERFORMANCE. **
                    FETCH inner_cursor INTO
                  :inner_product_name,
                  :inner_category_id;
               IF (inner_product_name IS NULL) THEN
                  EXIT;
               END IF;
               --** SSC-FDM-OR0035 - CHECK UDF IMPLEMENTATION FOR DBMS_OUTPUT.PUT_LINE_UDF. **
               call_results := (
                  CALL dbms_output.put_line( 'Category id: ' || NVL(outer_cursor.category_id :: STRING, ''))
               );
               --** SSC-FDM-OR0035 - CHECK UDF IMPLEMENTATION FOR DBMS_OUTPUT.PUT_LINE_UDF. **
               call_results := (
                  CALL dbms_output.put_line('Product name: ' || NVL(:inner_product_name :: STRING, ''))
               );
                 END LOOP;
                 CLOSE inner_cursor;
         END FOR;
         RETURN call_results;
      END;
   END;
$$;

Meilleures pratiques¶

Les curseurs imbriqués doivent être évités car ils peuvent avoir un impact négatif sur les performances et rendre le code plus complexe.
Au lieu de curseurs imbriqués, utilisez les fonctions SQL, telles que :
- Fonctions SQL
- Jointures
- Sous-requêtes
- Fonctions de fenêtre
- Expressions de table communes (CTEs)
- Requêtes récursives Ces alternatives traitent les données en masse et sont plus efficaces.
Pour toute assistance supplémentaire, contactez-nous à l’adresse suivante : snowconvert-support@snowflake.com

SSC-PRF-0006¶

Le curseur imbriqué à l’intérieur de la requête n’est pas pris en charge dans Snowflake.

Gravité¶

Aucun(e)

Description¶

Ce message apparaît lorsqu’une requête contient une définition de curseur. Lorsqu’une expression de curseur est évaluée, elle renvoie et ouvre automatiquement un curseur imbriqué. Pour plus de détails, voir Oracle Cursor Expression.

Exemples de code :¶

Entrée¶

 SELECT
  category_id,
  category_name,
  CURSOR (
    SELECT
      product_id,
      product_name || ', ' || category_id
    FROM
      products e
    WHERE
      e.category_id = d.category_id
  ) EMP_CUR
FROM
  categories d;

Sortie¶

 SELECT
  category_id,
  category_name,
  --** SSC-PRF-0006 - NESTED CURSOR INSIDE QUERY IS NOT SUPPORTED IN SNOWFLAKE. **
  CURSOR
    !!!RESOLVE EWI!!! /*** SSC-EWI-0108 - THE FOLLOWING SUBQUERY MATCHES AT LEAST ONE OF THE PATTERNS CONSIDERED INVALID AND MAY PRODUCE COMPILATION ERRORS ***/!!! (
    SELECT
      product_id,
      NVL(
      product_name :: STRING, '') || ', ' || NVL(category_id :: STRING, '')
    FROM
      products e
    WHERE
      e.category_id = d.category_id
  ) EMP_CUR
FROM
  categories d;

Meilleures pratiques¶

Nous vous recommandons d’éviter les curseurs, car ils peuvent nuire aux performances et rendre le code plus complexe.
Au lieu d’utiliser des curseurs imbriqués, envisagez les alternatives suivantes :
- Fonctions SQL
- Jointures
- Sous-requêtes
- Fonctions de fenêtre
- Expressions de table communes (CTEs)
- Requêtes récursives Ces options sont plus adaptées au traitement efficace de grandes quantités de données.
Pour toute assistance supplémentaire, contactez-nous à l’adresse suivante : snowconvert-support@snowflake.com

SSC-PRF-0007¶

PERFORMANCE REVIEW - CLUSTER BY

Description¶

Signale les cas où l’utilisation de CLUSTER BY peut entraîner des problèmes de performances.

Exemple de code¶

Teradata :¶

 CREATE MULTISET TABLE T_2008,
NO FALLBACK,
NO BEFORE JOURNAL,
NO AFTER JOURNAL,
CHECKSUM = DEFAULT,
DEFAULT MERGEBLOCKRATIO
(
      COL1 NUMBER(20,0) NOT NULL,
      COL2 INTEGER,
      COL3 VARCHAR(4) CHARACTER SET LATIN NOT CASESPECIFIC,
      COL4 DATE FORMAT 'YYYY-MM-DD'
)
PRIMARY INDEX 
( 
      COL1, COL2
)
PARTITION BY ( RANGE_N(COL4 BETWEEN DATE '2010-01-01' AND DATE '2025-12-31' EACH INTERVAL '1' YEAR ),
CASE_N(
COL3  = 'T',
COL3 = 'M',
COL3 = 'L') ); -- PARTITION BY transformed to CLUSTER BY

Snowflake :¶

CREATE OR REPLACE TABLE T_2008
(
      COL1 NUMBER(20,0) NOT NULL,
      COL2 INTEGER,
      COL3 VARCHAR(4),
      COL4 DATE
)
--** SSC-PRF-0007 - PERFORMANCE REVIEW - CLUSTER BY **
CLUSTER BY (
             !!!RESOLVE EWI!!! /*** SSC-EWI-0031 - RANGE_N FUNCTION NOT SUPPORTED ***/!!!
             RANGE_N(COL4 BETWEEN DATE '2010-01-01' AND DATE '2025-12-31' EACH INTERVAL '1' YEAR ),
!!!RESOLVE EWI!!! /*** SSC-EWI-0031 - CASE_N FUNCTION NOT SUPPORTED ***/!!!
CASE_N(
COL3  = 'T',
COL3 = 'M',
COL3 = 'L'))
COMMENT = '{ "origin": "sf_sc", "name": "snowconvert", "version": {  "major": 0,  "minor": 0,  "patch": "0" }, "attributes": {  "component": "teradata",  "convertedOn": "07/02/2025",  "domain": "no-domain-provided" }}'
; -- PARTITION BY transformed to CLUSTER BY

Transigez :¶

 CREATE TABLE my_table (
    enterprise_cif INT,
    name NVARCHAR(100),
    address NVARCHAR(255),
    created_at DATETIME
) 
WITH (
    DISTRIBUTION = HASH(enterprise_cif),
    CLUSTERED INDEX (enterprise_cif)
);

Snowflake :¶

 CREATE OR REPLACE TABLE my_table (
  enterprise_cif INT,
  name VARCHAR(100),
  address VARCHAR(255),
  created_at TIMESTAMP_NTZ(3)
)
--** SSC-PRF-0007 - PERFORMANCE REVIEW - CLUSTER BY **
CLUSTER BY (enterprise_cif)
COMMENT = '{ "origin": "sf_sc", "name": "snowconvert", "version": {  "major": 0,  "minor": 0,  "patch": "0" }, "attributes": {  "component": "transact",  "convertedOn": "10/09/2024" }}'
;

Meilleures pratiques¶

Examinez le code afin d’identifier d’éventuels problèmes de performances. Vous trouverez plus d’informations à ce sujet ici.
Si vous avez besoin de plus d’assistance, vous pouvez nous envoyer un e-mail à snowconvert-support@snowflake.com.

SSC-PRF-0008¶

Description¶

This message appears when SnowConvert AI detects loop usage in procedural code. Loops such as LOOP, WHILE, and FOR can lead to row-by-row processing and may degrade performance in Snowflake, especially when the loop iterates over large datasets or contains complex logic. The message is informational and prompts a review of the pattern.

Exemple de code¶

PostgreSQL:¶

CREATE OR REPLACE FUNCTION loop_example() RETURNS void AS $$
BEGIN
  FOR i IN 1..10 LOOP
    NULL;
  END LOOP;
END;
$$ LANGUAGE plpgsql;

Snowflake :¶

CREATE OR REPLACE PROCEDURE loop_example ()
RETURNS VARCHAR
LANGUAGE SQL
EXECUTE AS CALLER
AS
$$
  BEGIN
    --** SSC-PRF-0008 - PERFORMANCE REVIEW - LOOP USAGE **
    FOR i IN 1 TO 10
                     LOOP
      NULL;
    END LOOP;
  END;
$$;
;

Best practices¶

Prefer set-based SQL operations (SELECT, INSERT, UPDATE, DELETE) over row-by-row loops.
Avoid nested loops when possible; use joins, CTEs, or window functions instead.
If loops are required, keep iterations small and limit expensive operations inside the loop.
Consider refactoring procedural logic into single statements or bulk operations.

SSC-PRF-0009¶

CURSOR usage review

Gravité¶

Aucun(e)

Description¶

This message appears when SnowConvert AI detects a cursor declaration in procedural code. Cursors allow row-by-row processing of query results, which can lead to performance issues in Snowflake, especially when processing large datasets.

While cursors are valid in Snowflake Scripting, they introduce overhead because:

Each row is processed individually rather than as a set
Multiple round trips to the database may be required
Memory usage can be higher compared to set-based operations

This warning is informational and prompts a review of whether the cursor usage is necessary or can be replaced with more efficient set-based operations.

Exemple de code¶

Oracle¶

Entrée¶

CREATE OR REPLACE PROCEDURE get_first_employee AS
  CURSOR emp_cursor IS SELECT employee_id, first_name FROM employees;
  v_emp_id NUMBER;
  v_name VARCHAR2(100);
BEGIN
  OPEN emp_cursor;
  FETCH emp_cursor INTO v_emp_id, v_name;
  CLOSE emp_cursor;
END;

Sortie¶

CREATE OR REPLACE PROCEDURE get_first_employee ()
RETURNS VARCHAR
LANGUAGE SQL
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},{"attributes":{"component":"oracle"}}'
EXECUTE AS CALLER
AS
$$
  DECLARE
    --** SSC-PRF-0009 - PERFORMANCE REVIEW - CURSOR USAGE **
    emp_cursor CURSOR
    FOR
      SELECT employee_id, first_name FROM
        employees;
    v_emp_id NUMBER(38, 18);
    v_name VARCHAR(100);
  BEGIN
    OPEN emp_cursor;
    FETCH emp_cursor INTO
      :v_emp_id,
      :v_name;
    CLOSE emp_cursor;
  END;
$$;

Meilleures pratiques¶

Replace cursor-based row-by-row processing with set-based SQL operations (SELECT, INSERT, UPDATE, DELETE) whenever possible.
Use JOINs, subqueries, CTEs (Common Table Expressions), or window functions instead of cursors to process multiple rows efficiently.
If cursors are unavoidable, minimize the work done inside the cursor loop and avoid nested cursors.
Consider using MERGE statements for upsert operations instead of cursor-based conditional INSERT/UPDATE logic.
Pour toute assistance supplémentaire, contactez-nous à l’adresse suivante : snowconvert-support@snowflake.com

SSC-PRF-0010¶

Partition by removed, at least one of the specified expressions have no iceberg partition transform equivalent

Gravité¶

Aucun(e)

Description¶

Snowflake supports the PARTITION BY clause in Iceberg tables, however, only Iceberg partition transforms are supported. When transforming paritioning into Iceberg tables, SnowConvert AI will generate the equivalent partition transforms for supported cases. When no partition transform equivalent can be generated for the partition expressions, the PARTITION BY will be removed from the table by commenting it out with this PRF.

This PRF is only generated when SnowConvert AI migrates tables into Iceberg tables using the Tables translation conversion setting.

Exemples de code :¶

Entrée¶

 -- Additional Params: --TablesTransformationTarget SnowflakeIceberg
CREATE TABLE FINANCE.FINANCE_TABLE
(
  customerName VARCHAR(30),
  accountBalance VARCHAR(20)
)
PARTITION BY CASE_N(
accountBalance <  0 ,
accountBalance >=  0);

Sortie¶

 -- Additional Params: --TablesTransformationTarget SnowflakeIceberg
CREATE OR REPLACE ICEBERG TABLE FINANCE.FINANCE_TABLE
  (
 customerName VARCHAR,
 accountBalance VARCHAR
  )
  CATALOG = 'SNOWFLAKE'
--  --** SSC-PRF-0010 - PARTITION BY REMOVED, AT LEAST ONE OF THE SPECIFIED EXPRESSIONS HAVE NO ICEBERG PARTITION TRANSFORM EQUIVALENT **
--  PARTITION BY CASE_N(
--  accountBalance <  0 ,
--  accountBalance >=  0)
  COMMENT = '{ "origin": "sf_sc", "name": "snowconvert", "version": {  "major": 1,  "minor": 0,  "patch": "0.0" }, "attributes": {  "component": "teradata",  "convertedOn": "12/16/2025",  "domain": "no-domain-provided",  "migrationid": "9CebAVkM33qsfTnTrMh3Dw==" }}'
;

Meilleures pratiques¶

Analyze the impact of partitioning in the performance of queries over the generated Iceberg tables, if the difference is neglible then this PRF can be safely ignored.
Pour toute assistance supplémentaire, contactez-nous à l’adresse suivante : snowconvert-support@snowflake.com