如何将新元素添加到用户定义类型的数组？

Question

I have converted some stored procedure from Oracle to PostgreSQL but faced the below issue:

I have a user-defined type in PostgreSQL:

CREATE TYPE ut_merci_row AS (    
   SGLCNTNR varchar(100),
   CODEST_MERCEVARIA varchar(50), 
   CODCICLO smallint 
);

CREATE TYPE ut_merci_table AS (ut_merci_table UT_MERCI_ROW[]);

In Oracle:

  retTable UT_MERCI_TABLE := UT_MERCI_TABLE();
  .....
  retTable.extend;
  retTable(retTable.last) := UT_MERCI_ROW(rec.SGLCNTNR,rec.CODEST_MERCEVARIA,rec.CODCICLO);

Could you advise me how to convert the 2 last below code lines to PostgreSQL?

  retTable.extend;
  retTable(retTable.last) := UT_MERCI_ROW(rec.SGLCNTNR,rec.CODEST_MERCEVARIA,rec.CODCICLO);

Someone said that we don't need to "extend" the collection in PostgreSQL.

Answer 1

The second type definition is pretty redundant, just use ut_merci_row[] .

You don't have to “extend” an array in PostgreSQL, just assign to an index that is not yet used.

Answer 2

You can simply append the value to the array using the || concatenation operator. Make sure you initialize the variable to an empty array (otherwise it would null )

retTable ut_merci_row[] := '{}';

Then in the loop, just append a value of the type to the array:

retTable := rettable || row(rec.SGLCNTNR,rec.CODEST_MERCEVARIA,rec.CODCICLO)::ut_merci_row;

---

Trying to mimic Oracle's complicated way of returning tables with a cursor and custom types is not the right way to do this in Postgres.

But a much better solution would be to get rid of all that cursor processing and array handling and return a set of the base type:

CREATE OR REPLACE FUNCTION uf_getstatomerce1() 
  returns setof ut_merci_row
AS $body$
   SELECT DISTINCT row(m.SGLCNTNR, m.CODEST_MERCEVARIA, 1 as CODCICLO)::ut_merci_row
   from merce.DELIVERY_ORDER_RIF rif
     inner join merce.DELIVERY_ORDER_PARTITA pm on rif.DO_ID = pm.DO_ID
     inner join merce.vPARTITEMERCE m on pm.CODPARTITAMERCE = m.CODPARTITAMERCE;
$body$
LANGUAGE sql
STABLE;

In fact, in Postgres you also don't need a custom type for this, just declare the function as returns table and forget all the overhead:

CREATE OR REPLACE FUNCTION uf_getstatomerce1() 
  returns table (SGLCNTNR varchar, CODEST_MERCEVARIA varchar, CODCICLO smallint )
AS $body$
   SELECT DISTINCT row(m.SGLCNTNR, m.CODEST_MERCEVARIA, 1 as CODCICLO)::ut_merci_row
   from merce.DELIVERY_ORDER_RIF rif
     inner join merce.DELIVERY_ORDER_PARTITA pm on rif.DO_ID = pm.DO_ID
     inner join merce.vPARTITEMERCE m on pm.CODPARTITAMERCE = m.CODPARTITAMERCE;
$body$
LANGUAGE sql
STABLE;

The SQL function that simply returns a query will be much more efficient than the cursor loop.

In both cases, you can use it like this:

select *
from uf_getstatomerce1() ;