Updated on 2025-05-29 GMT+08:00

Use of Array Types

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

Syntax

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.
  • 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.

Precautions

  • GaussDB supports access to array elements using index syntax (enclosed by parentheses ()) and provides various dedicated functions (such as EXTEND, COUNT, FIRST, LAST, PRIOR, EXISTS, TRIM, NEXT, and DELETE) for flexible array operations and management.
  • 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.
  • 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 the elements of an array are of the collection 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 option for GUC parameter behavior_compat_options to verify the element length of the array or convert the element to the corresponding precision.
  • After the varray_compat option is enabled for the GUC parameter behavior_compat_options, 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.
  • If a stored procedure contains a DML statement (such as SELECT, UPDATE, INSERT, and 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.
  • NOT NULL syntax is not supported.

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;