Provided by: postgresql-doc-9.5_9.5.25-0ubuntu0.16.04.1_all 

NAME
SPI_push - push SPI stack to allow recursive SPI usage
SYNOPSIS
void SPI_push(void)
DESCRIPTION
SPI_push should be called before executing another procedure that might itself wish to use SPI. After
SPI_push, SPI is no longer in a “connected” state, and SPI function calls will be rejected unless a fresh
SPI_connect is done. This ensures a clean separation between your procedure's SPI state and that of
another procedure you call. After the other procedure returns, call SPI_pop to restore access to your own
SPI state.
Note that SPI_execute and related functions automatically do the equivalent of SPI_push before passing
control back to the SQL execution engine, so it is not necessary for you to worry about this when using
those functions. Only when you are directly calling arbitrary code that might contain SPI_connect calls
do you need to issue SPI_push and SPI_pop.
PostgreSQL 9.5.25 2021 SPI_PUSH(3)