laravel 建立数据库 索引怎么加

 
 
 我还没有找到任何规范版本中的任何内容，但我明白这一点 - 我是否正确？ 规范中是否有任何内容禁止评论和/或随机出现？ 有没有更强大的方式，我错过了？ 
 
 
 首先，最好使用ISO 32000-2或至少ISO 32000-1 PDF规范。 Adobe在这里发布了后者的一个版本; 该版本和ISO标准之间的技术资料是相同的，页码和章节号码也保留。 另一方面，根据Adobe个人的观点，Adobe PDF参考文献不被视为“规范性质”。 
 
 你的想法是xref部分后面总是跟着拖车，如果是这样的话，我可以在xref非常精确，如果使用交叉参考表 后，通过紧接着解析倒数第二个拖车 。 评论栏可能介于中间，但不是“随意的”。 
 
 另一方面，如果使用交叉引用流 ，则尾部信息被合并到交叉引用流字典中，考虑到交叉引用的偏移量，其实际上更容易找到。 

 
 
I'm yet to find anything in any of the specification versions that I have been following that is explicit about this though - am I correct? is there anything in the spec prohibiting comments and or random cruft appearing between? Is there a more robust way that I missed?
 
 
First of all it is preferable to use the ISO 32000-2 or at least the ISO 32000-1 PDF specification. Adobe published a version of the latter here; the technical material is identical between this version and the ISO Standard, the page and sections numbers are also preserved. The Adobe PDF References, on the other hand, are not considered "normative in nature" according to Adobe personal.
 
Your idea that xref section is always followed by the trailer and if so I can parse the penultimate trailer by following on immediately after the xref is quite accurate if cross reference tables are used. Comment lines may come in-between but not "random cruft".
 
If cross reference streams are used, on the other hand, the trailer information is merged into the cross reference stream dictionary which actually is even easier to find given the offset of the cross reference.