Sybase: Stored Procedure called from within another Stored Procedure is too slow

问题

I'm writing a stored procedure for a Sybase database. I'm using Sybase Central 16.0 as my development environment. The machine I'm using runs Microsoft Windows Server 2012 R2 Standard and has 16GB RAM running on a 2.8GHz CPU.

My stored procedure uses a cursor to iterate over the records in a table with about 400,000 reecords.  Each record is written incrementally into a LONG VARCHAR variable and every Nth record the proc will run an MD5 hash value on the variable and store the value in a separate table.

TABLE_NAME, DATE_TIME_RAN, FROM_RECORD, TO_RECORD, HASH_VALUE

If I run only the stored procedure to hash this table as a SQL block in SQL Anywhere (e.g.: BEGIN ... <hash the table here> ... END;) it goes through all records and completes successfully in about two minutes.  However if I run this stored procedure as an embedded command in another stored procedure (e.g.: CALL <MY_SCHEMA>.<MY_STORED_PROCEDURE>) then it never completes.

Why would running the stored procedure (on the same dataset) from within another stored procedure perform differently?

回答1:

Managed to find a much better solution to the issue without trawling through the table. I thought I'd post the solution here for anyone who might face a similar issue.

The requirement for the stored procedure was to loop through a large table one row at a time, concatenating the contents of every column in the row into a string and assigning this to a variable. Every N rows this variable's value would be written to a separate table. Previously I had been using a cursor to do this but a developer on our team discovered a much faster way using the WITH clause.

INSERT INTO <MY_SCHEMA>.<MY_TABLE_THAT_WILL_CONTAIN_THE_CONCATENATED_VALUES_OF_EVERY_N_ROWS>
WITH 
    CONCATENATE_ROWS AS (
            SELECT RANK() OVER (ORDER BY <PRIMARY_KEY_COLUMN>) AS ROWID, <PRIMARY_KEY_COLUMN>, <COLUMN_1> || '' || <COLUMN_2> || '' || ... <COLUMN_N> AS ROW_DETAIL
            FROM <MY_TABLE_THAT_I_AM_QUERYING> 
            ORDER BY <PRIMARY_KEY_COLUMN>
    ), 
    GROUPED_ROWS AS (
            SELECT (((CONCATENATE_ROWS.ROWID-1)/ <number of rows I want to concatenate, e.g.: 10>)+1) AS GROUPID, CAST(LIST(CONCATENATE_ROWS.ROW_DETAIL, '' ORDER BY <PRIMARY_KEY_COLUMN>) AS VARCHAR(4000)) AS CONCAT_DETAILS
             FROM CONCATENATE_ROWS 
             GROUP BY (((CONCAT_ORDERS.ROWID-1)/ <number of rows I want to concatenate, e.g.: 10>)+1)
    )
SELECT <Whatever columns I want to insert into <MY_TABLE_THAT_WILL_CONTAIN_THE_CONCATENATED_VALUES_OF_EVERY_N_ROWS>> 
FROM GROUPED_ROWS;

来源：https://stackoverflow.com/questions/54215723/sybase-stored-procedure-called-from-within-another-stored-procedure-is-too-slow