![]() ![]() This is very tricky bug (and very common). For these kinds of tasks PL/Perl, PL/Python or C procedures are strongly recommended in PostgreSQL.ĬREATE OR REPLACE FUNCTION collision(a integer) On the other hand, PL/pgPSM is not suitable for demanding computing tasks (the SQL statement execution cost is considerable). This feature ensures the compatibility of the types and functions of data with SQL. The interpreter itself is so minimalistic, that all logic and arithmetic operations are performed by SQL. This switch well demonstrates the fact that PL/pgPSM is mostly a preprocessor of SQL language. In such a case the system warns us, that only useless information appears in compilation time or returns unexpected values. It can be very helpful to find collisions of variable names and SQL attributes. The aim of this option is to dump the compiled code into the system logfile. These switches must be written before the PL/pgPSM function body together with the keyword# OPTION. The second switch invalidates all cached plans related to the function every time when the function is called. The first switch leads to the dumping of compiled code into the system log. ![]() PL/pgPSM has two function switches: DUMP and RECOMPILE. The PL/PgPSM contains the following statements:īefore starting to read about each statement, go through the following examples:ĬREATE OR REPLACE FUNCTION foo1(a integer)ĬREATE OR REPLACE FUNCTION foo2(a integer)ĬREATE OR REPLACE FUNCTION foo3(a integer) IF age >= 20 AND age =30 AND age get_sum.a) SET (name, surname, age) = (SELECT e.name, e.surname, e.age Both stored procedures select group of employees and call print_info for each group member. The following two examples show the same task, but the first implementation is considered wrong. the procedures should do concrete tasks, not only encapsulate the selects.take care about resources - use limited amount cursors and temporary tables,.avoid ISAM programming - use SQL if possible.use a prefix and qualified attribute name to avoid attribute and variable name collision,.There are also some extra recommendations for general SQL store procedure languages: do not write a long procedure (max 50 lines).Take a big care about a readable and clear code: The same tips as for all software development are recommended for code writing in PL/pgPSM. SET real_name = (SELECT name || ' ' || surname PostgreSQL implementation is called PL/pgPSM (using the standard naming scheme in PostgreSQL).ĬREATE OR REPLACE FUNCTION hello(uid integer) Implementation of SQL/PSM is usually incomplete, SQL PL in DB2 is considered to be one of the best implementations. After 2005 the SQL/PSM standard started to become more popular, when it was implemented in Advantage Database Server (Sybase iAnywhere, 2005), MySQL (2005) and PostgreSQL (2007). Except for DB2 (SQL PL, IBM, 2001) all of them were minor RDBMS: Miner, Solid, 602SQL Server. SQL/PSM was implemented only in those RDBMS, in which there was no support for stored procedures before 1998. Unfortunately at that time most big companies had their own languages (incompatible with the standard) and refused to abandon them in favor of standard. In 1998 a draft of the new standard became part of SQ元 - under the name SQL/PSM (ANSI/ISO/IEC 9075-4:1999). From 1990 a group of developers around Jim Melton, part of the the ANSI SQL commission for standards, started to work on this problem. The most popular ones included PL/SQL (Oracle 1992), T-SQL (Sybase and Microsoft, 1995) and SPL (Informix, 1996). Commercial databases started implementing their own proprietary languages for this purpose. 5 Porting stored procedures from MySQL 5.xĪlready in the early nineties of the 20th century it was obvious that the ANSI SQL standard lacks means for creating stored procedures (especially working with variables and flow control - loops and conditionals).2 Tips for developing in PL/pgPSM language.
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