Help Center/ GaussDB/ Developer Guide(Centralized_8.x)/ Stored Procedure/ Arrays, Collections, and Records/ Arrays/ Use of Array Types
Updated on 2024-08-20 GMT+08:00
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Use of Array Types

Before the use of arrays, an array type needs to be defined:

Define an array type immediately after the AS keyword in a stored procedure. The definition method is as follows: 
TYPE array_type IS VARRAY(size) OF data_type;

Related parameters are as follows:

  • array_type: indicates the name of the array type to be defined.
  • VARRAY: indicates the array type to be defined.
  • size: indicates the maximum number of members in the array type to be defined. The value is a positive integer.
  • data_type: indicates the types of members in the array type to be created.
  • In GaussDB, the array automatically increases. If out-of-bounds access occurs, a NULL value is returned and no error is reported. After the varray_compat parameter is enabled, the index check is added. If out-of-bounds access occurs, an error is reported.
  • The scope of an array type defined in a stored procedure takes effect only in this storage process.
  • The size information is recorded in the pg_type system catalog. After the varray_compat parameter is enabled, the length and index of array operations are checked. If the parameter is disabled, the size information is not used.
  • data_type can also be the record type defined in a stored procedure (anonymous blocks are not supported) or set type, but cannot be the array or cursor type defined in the stored procedure.
  • When data_type is collection, multi-dimensional arrays are not supported.
  • NOT NULL syntax is not supported.
  • The constructors of the array type can be used only in A-compatible mode.
  • The constructor of the array type cannot be used as the default value of a function or stored procedure parameter.
  • If an array is an element of the set type and data_type of the array is set to varchar or numeric that can define the length and precision, you need to enable the tableof_elem_constraints parameter (behavior_compat_options is set to tableof_elem_constraints) to verify the element length of the array or convert the element to the corresponding precision.
  • After the varray_compat parameter is enabled (the behavior_compat_options parameter is set to varray_compat), the array type defined in the anonymous block cannot be used after ROLLBACK is executed or EXCEPTION occurs in the anonymous block.
  • After enable_recordtype_check_strict is set to on, if the member is of the record type and a column of the record type has the not null or default attribute, an error is reported during stored procedure or package compilation.

GaussDB supports access to array elements by using parentheses, and it also supports the extend, count, first, last, prior, exists, trim, next, and delete functions.

  • If a stored procedure contains a DML statement (such as SELECT, UPDATE, INSERT, or DELETE), you are advised to use square brackets to access array elements. Using parentheses will access arrays by default. If no array exists, function expressions will be identified.
  • When the CLOB size is greater than 1 GB, the table of type, record type, and CLOB cannot be used in the input or output parameter, cursor, or raise info in a stored procedure.

Examples

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-- Perform array operations in the stored procedure.
gaussdb=# CREATE OR REPLACE PROCEDURE array_proc AS
DECLARE 
       TYPE ARRAY_INTEGER IS VARRAY(1024) OF INTEGER;--Define the array type.
       ARRINT ARRAY_INTEGER: = ARRAY_INTEGER();  --Declare the variable of the array type.
BEGIN 
       ARRINT.extend(10);  
       FOR I IN 1..10 LOOP  
               ARRINT(I) := I; 
       END LOOP; 
       DBE_OUTPUT.PRINT_LINE(ARRINT.COUNT);  
       DBE_OUTPUT.PRINT_LINE(ARRINT(1));  
       DBE_OUTPUT.PRINT_LINE(ARRINT(10)); 
       DBE_OUTPUT.PRINT_LINE(ARRINT(ARRINT.FIRST)); 
       DBE_OUTPUT.PRINT_LINE(ARRINT(ARRINT.LAST));
       DBE_OUTPUT.PRINT_LINE(ARRINT(ARRINT.NEXT(ARRINT.FIRST)));
       DBE_OUTPUT.PRINT_LINE(ARRINT(ARRINT.PRIOR(ARRINT.LAST)));
       ARRINT.TRIM();
       
       IF ARRINT.EXISTS(10) THEN
           DBE_OUTPUT.PRINT_LINE('Exist 10th element');
       ELSE
           DBE_OUTPUT.PRINT_LINE('Not exist 10th element');
       END IF;
       DBE_OUTPUT.PRINT_LINE(ARRINT.COUNT);
       DBE_OUTPUT.PRINT_LINE(ARRINT(ARRINT.FIRST)); 
       DBE_OUTPUT.PRINT_LINE(ARRINT(ARRINT.LAST));
       ARRINT.DELETE();
END;  
/

-- Call the stored procedure to display the result.
gaussdb=# CALL array_proc();
10
1
10
1
10
2
9
Not exist 10th element
9
1
9
 array_proc
------------

(1 row)

-- Drop the stored procedure.
gaussdb=# DROP PROCEDURE array_proc;
Parent topic: Arrays