Function init_sql_fcache

src/backend/executor/functions.c:679–932

* Initialize the SQLFunctionCache for a SQL function */

 * Initialize the SQLFunctionCache for a SQL function
 */
static void
init_sql_fcache(FunctionCallInfo fcinfo, Oid collation, bool lazyEvalOK)
{
	FmgrInfo   *finfo = fcinfo->flinfo;
	Oid			foid = finfo->fn_oid;
	MemoryContext fcontext;
	MemoryContext oldcontext;
	Oid			rettype;
	TupleDesc	rettupdesc;
	HeapTuple	procedureTuple;
	Form_pg_proc procedureStruct;
	SQLFunctionCachePtr fcache;
	List	   *queryTree_list;
	List	   *resulttlist;
	ListCell   *lc;
	Datum		tmp;
	bool		isNull;

	/*
	 * Create memory context that holds all the SQLFunctionCache data.  It
	 * must be a child of whatever context holds the FmgrInfo.
	 */
	fcontext = AllocSetContextCreate(finfo->fn_mcxt,
									 "SQL function",
									 ALLOCSET_DEFAULT_SIZES);

	oldcontext = MemoryContextSwitchTo(fcontext);

	/*
	 * Create the struct proper, link it to fcontext and fn_extra.  Once this
	 * is done, we'll be able to recover the memory after failure, even if the
	 * FmgrInfo is long-lived.
	 */
	fcache = (SQLFunctionCachePtr) palloc0(sizeof(SQLFunctionCache));
	fcache->fcontext = fcontext;
	finfo->fn_extra = (void *) fcache;

	/*
	 * get the procedure tuple corresponding to the given function Oid
	 */
	procedureTuple = SearchSysCache1(PROCOID, ObjectIdGetDatum(foid));
	if (!HeapTupleIsValid(procedureTuple))
		elog(ERROR, "cache lookup failed for function %u", foid);
	procedureStruct = (Form_pg_proc) GETSTRUCT(procedureTuple);

	/*
	 * copy function name immediately for use by error reporting callback, and
	 * for use as memory context identifier
	 */
	fcache->fname = pstrdup(NameStr(procedureStruct->proname));
	MemoryContextSetIdentifier(fcontext, fcache->fname);

	/*
	 * Resolve any polymorphism, obtaining the actual result type, and the
	 * corresponding tupdesc if it's a rowtype.
	 */
	(void) get_call_result_type(fcinfo, &rettype, &rettupdesc);