2024 ，pgvector如何使你龙年识别真龙

前文

AI识别必定是未来的主流技术，数据库作为后端的关键核心服务，必须紧跟时代潮流。pgvector向量数据库横空出世，它可以把物体以多种特征变量存储在数据库里面，并且通过简单的SQL实现，对相似物体进行比较确认。

基于postgresql的一个扩展插件，与postgresql强强联手可以实现向量数据的存储、计算。

imgsmlr同样也是基于postgresql的一个扩展插件，它可以把非结构化文件转向成识别二进制数据，二进制再转换成特征数据，最后为转换成二进制数据做铺垫。流程如图，结果是我们从图片中识别出来的真龙， 千万图片丛中过，我只找属于我自己的真龙。

环境准备

安装 postgreSQL14

我的环境安装包如下，注意libs和devel都必须要有

[root@server128 ~]# rpm -qa |grep -i postgres
postgresql14-14.10-1PGDG.rhel7.x86_64
postgresql-libs-9.2.24-9.el7_9.x86_64
postgresql14-libs-14.10-1PGDG.rhel7.x86_64
postgresql14-server-14.10-1PGDG.rhel7.x86_64
postgresql14-devel-14.10-1PGDG.rhel7.x86_64

安装imgsmlr

git clone --depth 1 https://github.com/postgrespro/imgsmlr  
  
  
cd imgsmlr/  
USE_PGXS=1 make   执行报错，见下图 
 
USE_PGXS=1 make install  
​

解决方法如下，在/usr/pgsql-14/include/server/access/gist.h的259行位置加入以下注释，即可以成功编译通过USE_PGXS=1 make

​
#ifndef FALSE
#define FALSE   (0)
#endif
​
#ifndef TRUE
#define TRUE    (!FALSE)
#endif

安装pgvector

git clone  https://github.com/pgvector/pgvector.git
cd pgvector
make
make install

准备语句

#img_raw装载图片
create table  img_raw(
rawid int primary key,
info   text,
ts timestamp,
raw  bytea
);
​
#img_vec装载图片的特征数据
create table  img_vec(
id  int  primary key  references img_raw(rawid),
patt   pattern,
sig signature
);
​
# 基于img_vec表构建gist
create index on   img_vec  using  gist(sig);
​
​
​
#插入图片信息
​
insert into img_raw values (1, 'long1,png', now(), pg_read_binary_file('/img/long1.jpg'));  
insert into img_raw values (2, 'long2,jpg', now(), pg_read_binary_file('/img/long2.jpg'));  
insert into img_raw values (3, 'long3,jpg', now(), pg_read_binary_file('/img/long3.jpg'));  
insert into img_raw values (4, 'long4,jpg', now(), pg_read_binary_file('/img/long4.jpg'));  
insert into img_raw values (5, 'long5,jpg', now(), pg_read_binary_file('/img/long5.jpg'));  
insert into img_raw values (6, 'long6,jpg', now(), pg_read_binary_file('/img/long6.jpg'));  
insert into img_raw values (7, 'long7,jpg', now(), pg_read_binary_file('/img/long7.jpg'));  
insert into img_raw values (8, 'long8,jpg', now(), pg_read_binary_file('/img/long8.jpg'));  
insert into img_raw values (9, 'long9,jpg', now(), pg_read_binary_file('/img/long9.jpg'));  
insert into img_raw values (10, 'long10,jpg', now(), pg_read_binary_file('/img/long10.jpg'));  
insert into img_raw values (11, 'long11,jpg', now(), pg_read_binary_file('/img/long11.jpg')); 
​
insert into img_raw values (12, 'chang1,jpg', now(), pg_read_binary_file('/img/chang1.jpg')); 
insert into img_raw values (13, 'hu1,jpg', now(), pg_read_binary_file('/img/hu1.jpg')); 
insert into img_raw values (14, 'mao1,jpg', now(), pg_read_binary_file('/img/mao1.jpg')); 
insert into img_raw values (15, 'she1,jpg', now(), pg_read_binary_file('/img/she1.jpg')); 
insert into img_raw values (16, 'tian1,jpg', now(), pg_read_binary_file('/img/tian1.jpg')); 
insert into img_raw values (17, 'wo1,jpg', now(), pg_read_binary_file('/img/wo1.jpg')); 
insert into img_raw values (18, 'xiong1,jpg', now(), pg_read_binary_file('/img/xiong1.jpg')); 
insert into img_raw values (19, 'tu1,jpg', now(), pg_read_binary_file('/img/tu1.jpg')); 
insert into img_raw values (20, 'tu2,jpg', now(), pg_read_binary_file('/img/tu2.jpg')); 
insert into img_raw values (21, 'tu3,jpg', now(), pg_read_binary_file('/img/tu3.jpg'));
​
​
#将图片提取所有特征保存img_vec表里面
insert into img_vec select rawid, jpeg2pattern(raw), pattern2signature(jpeg2pattern(raw)) from img_raw;
​
#img_vec表添加向量embedding
alter table img_vec add column embedding vector;
​
​
# img_vec表的特征数据转化为向量数据
update img_vec set embedding = replace(replace(sig::text, '(', '{'), ')', '}')::float[]::vector;  
​
​
​
select   
    t1.id,  
    t2.info,  
    embedding <-> (select embedding from img_vec where id=9) as "欧氏相似距离"  
  from img_vec t1 join img_raw t2 on t1.id=t2.rawid  
    order by embedding <-> (select embedding from img_vec where id=9)
    
    
    
​

实践：福龙与狗 、熊、兔、蜗牛、植物射手

用自己拍照21张，针对福龙从不同角度拍了10张，与及其它各式小动物共11张，在postgresql转换成向量数据后，用使用欧氏算法、内积算法、余弦算法来进行计算

为了证明这个是龙，看它的标签

以long9作为标准图，计算其它图片与它的相似度
​
#用使用欧氏算法,<->来进行计算
postgres=# select
postgres-#     t1.id,
postgres-#     t2.info,
postgres-#     embedding <-> (select embedding from img_vec where id=9) as "欧氏相似距离"
postgres-#   from img_vec t1 join img_raw t2 on t1.id=t2.rawid
postgres-#     order by embedding <-> (select embedding from img_vec where id=9);
 id |    info    |    欧氏相似距离
----+------------+--------------------
  9 | long9,jpg  |                  0
  4 | long4,jpg  | 0.8131946015532012
 14 | mao1,jpg   |  0.873532153956551
  5 | long5,jpg  | 0.9437004404760417
  3 | long3,jpg  |  1.006888032114946
  2 | long2,jpg  | 1.0538826025705688
 17 | wo1,jpg    | 1.0584338866296883
  8 | long8,jpg  | 1.1284268427144581
  1 | long1,png  | 1.1660293246028335
 10 | long10,jpg | 1.1743752827626244
  7 | long7,jpg  | 1.1849544245168537
 11 | long11,jpg | 1.2636647526394387
 18 | xiong1,jpg |   1.28623207769336
 16 | tian1,jpg  | 1.2928207635465576
  6 | long6,jpg  |  1.415787966613027
 15 | she1,jpg   |  1.472345617909073
 12 | chang1,jpg | 1.5688576102868548
 13 | hu1,jpg    | 1.5765029578406513
 19 | tu1,jpg    | 1.6046681136433938
 21 | tu3,jpg    | 1.9848909683454863
 20 | tu2,jpg    |  1.996557491652661
(21 rows)
​
​
#内积算法  <#>来进行计算
postgres=# select
postgres-#     t1.id,
postgres-#     t2.info,
postgres-#     embedding <#> (select embedding from img_vec where id=9) as "内积相似距离"
postgres-#   from img_vec t1 join img_raw t2 on t1.id=t2.rawid
postgres-#     order by embedding <#> (select embedding from img_vec where id=9)  ;
 id |    info    |    内积相似距离
----+------------+---------------------
  9 | long9,jpg  |  -9.793889999389648
 15 | she1,jpg   |   -9.56818962097168
  5 | long5,jpg  |  -9.520377159118652
 10 | long10,jpg |  -9.336055755615234
  4 | long4,jpg  |   -9.27934455871582
  8 | long8,jpg  |  -9.063756942749023
 20 | tu2,jpg    |  -9.029650688171387
  1 | long1,png  |  -8.906010627746582
 11 | long11,jpg |  -8.879608154296875
  3 | long3,jpg  |  -8.859291076660156
  2 | long2,jpg  |  -8.828414916992188
  7 | long7,jpg  |  -8.590826034545898
  6 | long6,jpg  |   -8.51888656616211
 14 | mao1,jpg   |  -8.475362777709961
 17 | wo1,jpg    | -7.8920063972473145
 12 | chang1,jpg |  -7.692102432250977
 16 | tian1,jpg  |  -7.567811965942383
 13 | hu1,jpg    |    -6.4823317527771
 18 | xiong1,jpg |  -6.195792198181152
 19 | tu1,jpg    |  -5.272591590881348
 21 | tu3,jpg    |    -4.3834547996521
(21 rows)
​
#余弦算法  <=> 来进行计算
postgres=# select
postgres-#     t1.id,
postgres-#     t2.info,
postgres-#     embedding <=> (select embedding from img_vec where id=9) as "余弦相似距离"
postgres-#   from img_vec t1 join img_raw t2 on t1.id=t2.rawid
postgres-#     order by embedding <=> (select embedding from img_vec where id=9);
 id |    info    |     余弦相似距离
----+------------+----------------------
  9 | long9,jpg  |                    0
  4 | long4,jpg  |    0.034229251128992
 14 | mao1,jpg   |  0.03767662614530476
 18 | xiong1,jpg | 0.039896219019039614
  5 | long5,jpg  |  0.04453997228870388
  3 | long3,jpg  |  0.05313360470652673
 17 | wo1,jpg    |  0.05427983467295261
  2 | long2,jpg  |  0.05828036923202573
  8 | long8,jpg  |  0.06559011022972738
 10 | long10,jpg |  0.06853261342194783
  1 | long1,png  |  0.07069949063544745
  7 | long7,jpg  |  0.07420155647983717
 19 | tu1,jpg    |  0.07621919722304038
 11 | long11,jpg |  0.08243281628522736
 16 | tian1,jpg  |  0.08686050822976776
 15 | she1,jpg   |  0.09882522468462784
  6 | long6,jpg  |   0.1048961893306749
 13 | hu1,jpg    |  0.12904889503224415
 12 | chang1,jpg |  0.13378521110088515
 20 | tu2,jpg    |  0.17567972259493136
 21 | tu3,jpg    |   0.1793031852332665
(21 rows)
​
​
​

上面的计算结果不理想，反复查看，最后发现long9右边有鼓起的红包，特征收集钱包的信息，我把long9改成long6,重新运行欧氏相似距离计算，这样发现前5名都是long的收集结果，而且long6与long9离得老远！

实践:龙与猫

我在网络上随机摘了6个猫的图，以及5个龙的图，这下子可以确定照片来自于不同的拍摄工具、不同的照片格式、不同的编码方式、不同的分辨率、不同的大小。

​
​
postgres=#   select
postgres-#     t1.id,
postgres-#     t2.info,
postgres-#     embedding <-> (select embedding from img_vec where id=9) as "欧氏相似距离"
postgres-#   from img_vec t1 join img_raw t2 on t1.id=t2.rawid
postgres-#     order by embedding <-> (select embedding from img_vec where id=9)
postgres-#     limit 20;
 id |   info   |    欧氏相似距离
----+----------+--------------------
  9 | d3,jpg   |                  0
  7 | d1,jpeg  | 0.7647856568512812
  8 | d2,jpeg  | 1.2676685459702477
  5 | cat4,png | 1.3949615071226016
  6 | cat5,jpg |  1.464445502504794
  3 | cat3,jpg | 1.7297577441389917
 11 | d5,jpg   |  2.441273726871975
  1 | cat1,png |  2.449192466777335
  2 | cat2,jpg |  2.623407880151245
 10 | d4,jpeg  | 2.8941867638822063
  4 | cat4,jpg |  4.956624524660588
(11 rows)
​
postgres=#   select
postgres-#     t1.id,
postgres-#     t2.info,
postgres-#     embedding <#> (select embedding from img_vec where id=9) as "内积相似距离"
postgres-#   from img_vec t1 join img_raw t2 on t1.id=t2.rawid
postgres-#     order by embedding <#> (select embedding from img_vec where id=9)
postgres-#     limit 20;
 id |   info   |    内积相似距离
----+----------+---------------------
 11 | d5,jpg   | -13.741656303405762
 10 | d4,jpeg  | -12.781399726867676
  1 | cat1,png | -11.762970924377441
  2 | cat2,jpg |  -9.446988105773926
  5 | cat4,png |  -8.874711036682129
  9 | d3,jpg   |   -8.14848518371582
  4 | cat4,jpg |  -8.092750549316406
  7 | d1,jpeg  |   -7.85388708114624
  3 | cat3,jpg |  -6.499306678771973
  8 | d2,jpeg  |  -5.019601821899414
  6 | cat5,jpg |  -4.994093418121338
(11 rows)
​
postgres=#   select
postgres-#     t1.id,
postgres-#     t2.info,
postgres-#     embedding <=> (select embedding from img_vec where id=9) as "余弦相似距离"
postgres-#   from img_vec t1 join img_raw t2 on t1.id=t2.rawid
postgres-#     order by embedding <=> (select embedding from img_vec where id=9)
postgres-#     limit 20;
 id |   info   |     余弦相似距离
----+----------+----------------------
  9 | d3,jpg   |                    0
  7 | d1,jpeg  |  0.03589936156946816
 11 | d5,jpg   | 0.042836060244666685
  8 | d2,jpeg  |  0.05975859196041422
  5 | cat4,png |  0.08507819244719383
  1 | cat1,png |   0.1087175221334512
 10 | d4,jpeg  |  0.11832410643368074
  6 | cat5,jpg |  0.12351988272197956
  3 | cat3,jpg |   0.1869637379378707
  2 | cat2,jpg |   0.2117638205685053
  4 | cat4,jpg |   0.5035052630227678
(11 rows)

上面结论来看，这来自四面八方不同的图片使用三种算法，余弦距离计算的功能最好，前面三名都是龙有关的。

结论

• imgsmlr和pgvector是好东西，但是要注意图片的特征值的抽取，例如同样的手机拍摄 ，因为 识别目标旁边放的东西，向量化计算时会大打折扣。

• imgsmlr和pgvector虽好，但是没有可以监测的调试环境，如何改变特征值？如何在内部对图像进行观测？目前还没有这个功能

• pgvector以后在AI大模型领域必定大有作为，目前识别虽有误差，但是识别有80%以上的通过 ， 以后进一步的发展， 通过后端与前端的合力，必定可以识别100%的真龙。

  最后预祝各位同学龙年遇真龙，龙年大乐！