SPI_push — push SPI stack to allow recursive SPI usage
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.
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