Problem description: When postgresql is used as zabbix database, LLD macro {#I} is not resolved when, for example, it is used in a preprocessing step of an item prototype. Such problem doesn't occur for exactly the same setup and MySQL.

Steps to reproduce:

1. Create a trapper item (type of information = text)
2. Create a low level discovery rule that depends on this item
3. Specify the following macros for the LLD:
   {#ID} => $.id
   {#X} => $.index
4. Create an item prototype with the following parameters:
   Type = Dependent item
   Key = item{#ID}
   Master item = the previously created trapper item
   Type of information = text
5. Add the following preprocessing step to the item prototype:
   Name = JSONPath
   Parameters = $.[ {#X}].id
6. Send the following string to the trapper item created in step 1:

   [{"id":101,"index":"0","path":"$.[0].value","dataSrc":"value","value":"test1"}]
   

   Notice that the received data was successfully processed and an item with key item[101] was discovered.

7. Change macro {#X} to {#I} in LLD macros and in the preprocessing step of the created item prototype.
8. Remove the previously discovered item with key item[101]
9. Send the same string again to the trapper item created in step 1:

   [{"id":101,"index":"0","path":"$.[0].value","dataSrc":"value","value":"test1"}]
   

Result: Item was not discovered, the following error is observed in info column for the discovery rule:

Cannot create item: invalid value for preprocessing step #1: unsupported construct in jsonpath starting with: "{#I}].id".

Expected: item should be discovered, no error should be observed.

P.S. I've checked the same scenario for MySQL, and the item got successfully discovered using macro {#I}

Example: