remove the code of C function

Author: bigplaice

CN/modules/ROOT/pages/master/oracle_builtin_functions/vsize.adoc

@@ -59,58 +59,6 @@ IMMUTABLE;
 /* End - VSIZE */
 ```
 
-C 函数实现（`misc_functions.c`）：
-```c
-Datum
-ora_vsize(PG_FUNCTION_ARGS)
-{
-	Datum		value = PG_GETARG_DATUM(0);
-	int32		result;
-	int			typlen;
-
-	/* On first call, get the input type's typlen, and save at *fn_extra */
-	if (fcinfo->flinfo->fn_extra == NULL)
-	{
-		/* Lookup the datatype of the supplied argument */
-		Oid			argtypeid = get_fn_expr_argtype(fcinfo->flinfo, 0);
-
-		typlen = get_typlen(argtypeid);
-		if (typlen == 0)		/* should not happen */
-			elog(ERROR, "cache lookup failed for type %u", argtypeid);
-
-		fcinfo->flinfo->fn_extra = MemoryContextAlloc(fcinfo->flinfo->fn_mcxt,
-													  sizeof(int));
-		*((int *) fcinfo->flinfo->fn_extra) = typlen;
-	}
-	else
-		typlen = *((int *) fcinfo->flinfo->fn_extra);
-
-	if (typlen == -1)
-	{
-		/*
-		 * varlena type.  toast_raw_datum_size() normalizes 1-byte/4-byte
-		 * headers, compression and external (toasted) storage to the
-		 * logical (decompressed) size using the 4-byte header convention,
-		 * so subtracting VARHDRSZ yields the payload byte count in every
-		 * case -- the same pattern octet_length() uses.
-		 */
-		result = toast_raw_datum_size(value) - VARHDRSZ;
-	}
-	else if (typlen == -2)
-	{
-		/* cstring */
-		result = strlen(DatumGetCString(value)) + 1;
-	}
-	else
-	{
-		/* ordinary fixed-width type */
-		result = typlen;
-	}
-
-	PG_RETURN_INT32(result);
-}
-```
-
 == VSIZE 典型用例
 [cols="8,2"]
 |====