I'm working on an application which is a large database of chemical substances (approx 250,000 but rising) and associated data. I'm looking at ways to optimise the way searching is performed.
The application is running under PHP 7.0.27, MariaDB 5.5.56, and Apache 2.4.6
The application allows searching by chemical name and various chemical codes (such as EC number and CAS number). The schema is such that there are separate tables to hold the data, and the relationships of which codes apply to which chemicals.
These tables are in the database:
substances - unique ID and name for each chemical substance.
ecs - a list of EC Numbers
ecs_substances - which EC Number(s) apply to which substances
cas - a list of CAS Numbers
cas_substances - which CAS Number(s) apply to which substances
Note: there are other tables than the ones above where similar logic will apply, but for now I want to focus on these for this example.
It is possible for a substance to have multiple EC/CAS numbers, and a small number do not have them - i.e. it's not a simple 1:1 relationship.
The application has search fields for the substance name (substances.name), EC number (ecs.value) CAS number (cas.value). These can be used on their own, or in conjuction with each other. For example: find a substance by name, or find a substance by name and CAS number.
I believe the "quickest" way of performing a search for any given value would be to use a LIKE condition on the specific table required. So if I want to look up substances which have "acids" as part of the name:
SELECT id FROM substances WHERE name LIKE '%acids%' LIMIT 0,250
However the results that the application gives are shown in a table which includes headings for substance name, CAS number, EC number. It also allows the results to be ordered on a column (e.g. order by substance name, CAS, EC, etc). This requires JOIN conditions.
I'm doing it like this:
$sql = 'SELECT
DISTINCT(substances.`id`),
substances.`name`,
"" AS cas_number,
"" AS ec_number
FROM
substances ';
// Search - EC Number, or if trying to order by EC column (JOIN has to occur to make that possible)
if ( (isset($search['ecNumber'])) || (isset($order['column']) && ($order['column'] == 'ec_number')) ) {
$sql .= ' LEFT JOIN ecs_substances ON substances.id = ecs_substances.substance_id LEFT JOIN ecs ON ecs_substances.ec_id = ecs.id ';
}
// Search - CAS Number, or if trying to order by CAS column (JOIN has to occur to make that possible)
if ( (isset($search['casNumber'])) || (isset($order['column']) && ($order['column'] == 'cas_number')) ) {
$sql .= ' LEFT JOIN cas_substances ON cas_substances.substance_id = substances.id LEFT JOIN cas ON cas_substances.cas_id = cas.id ';
}
The problem is that because of all the JOINs that are occurring it's slowing down how quickly the results can be obtained.
Benchmark: The first query I posted which just uses a LIKE condition on 1 table will execute in 140ms, whereas it's taking 506ms for the same search criteria with all of the JOIN statements in the second block of code.
I'd like to know if there are ways to optimise this such that the time taken to present results to the user decreases.
It's worth mentioning that the results are displayed in DataTables and PHP is producing a JSON feed of the results. The LIMIT 0,250 is something the end user can override by setting results per page, but I'm happy to limit them to say no more than 500 per page.
Some things I've looked into are:
Caching the JSON. Not a big fan of this because the data is updated quite regularly. The data presented must always be what is in the database, not some cached copy.
Do a search on the required table as in the first code sample. Update the other columns with ajax. This would "appear" to give instant results on the column the user has searched and then quickly thereafter populate the other columns required by the DataTable. This seems incredibly fiddly to do and I don't know whether it's really a good idea.
Consider FULLTEXT because it allows for much faster searching than LIKE with a leading wildcard %. `MATCH(col) AGAINST('+acid' IN BOOLEAN MODE)
Sounds like you need a "many:many" mapping table. Tips on efficiency in such: http://mysql.rjweb.org/doc.php/index_cookbook_mysql#many_to_many_mapping_table
Consider using GROUP_CONCAT(cas) for provideing a comma-list of CASs.
JSON does not seem practical. And even less so since you are using only MySQL 5.5.
I think a response time of half a second is quite good, given what you want to do. You must have done all necessary database optimizations? (db type, indexes, etc).
There are several things you could explore:
Prepare all possible searches and store them in a database for quick access. This may sound stupid but this is how I often achieve fast searches. It's difficult for me to judge what the best way to do this, with your data, would be. You could start by adding a TEXT column to your substances table and store all the information about the substance in it: It's name, and all EC/CAS numbers. Separate the items with something like '|', or any other character not used in searches. I would call that the 'search' column. Alternatively you could make a new table, just for searching with that column in it, and the id of the substance. Now you can make one search input field for all three types of data and search in one column only. Would that work for you? Would it be faster? Possibly, but I cannot guarantee it. I don't know, but it's quite easy to try. There is a disadvantage: You would have to update that column with every change in the database.
Use a proper search engine. Several are available for mariadb. Start at: https://mariadb.com/kb/en/library/about-sphinxse It basically does something far more advanced than what I described under point 1: Prepare a database with data for optimized searching.
Still, a response of half a second would be something I could live with.
I have two tables, one with all the correct names of people in it, and then I have a table with all the correct names plus a bunch of names where there is some kind of misspell in the name, or using other characters.
For example, we got a name like Henry Muller, and then one with Henry Müller or Henry Mueller, and many other variations like that.
Is there some kind of mysql function that can compare those names to match 90% of the characters or something similiar? I know I cant match all the names to the correct ones, but I am hoping to get some of the way.
Its in a mysql database - but wouldnt mind getting the job done in php.
Thanks a whole bunch:)
I think this will accomplish what you're after, but you'll have to deal with the possibility of false matches
SELECT A.name, B.name
FROM TABLE_A A
INNER JOIN TABLE_B B
ON Soundex(A.name) = Soundex(B.name)
Well I'm having a problem mainly caused by bad structure in database. I'm coding this for a company whose code is quite messy and the table is very large so I don't think it's an option to fix the structure.
Anyway, my issue is that I'm trying to somehow group a value that won't be alone in the string...
They are storing values separated with commas... So it would be like
field: "category" value: 'var1, var2, var3'
And I will search using this query:
SELECT name, category
FROM companies
WHERE (MATCH(name, category) AGAINST ('$search' IN BOOLEAN MODE)
OR category LIKE '$search%')
It would match with for example var2 (it's not limited to 3 variables though, can be solo or many more) and I'd split it manually in PHP, no problem. Although I will not get enough matches, I want e.g. 10 matches by different searches. To be more specific I'm making an autosuggest feature, which means I will for example want to match "moto%" with motorbike, motor alone or whatever but I keep getting the same values, like there'd be a couple of 100 of results that contains "motorbike" and I don't know how to filter them, as I'm not able to use GROUP BY due to bad db structure...
I found this: T-SQL - GROUP BY with LIKE - is this possible?
It SEEMED as something that would be a solution, but as far as I've tried I could not get it work with what I wanted.
So I'm wondering which solutions there are... If there are ABSOLUTELY no way of working this around I might probably have to fix the db structure (but this really has to be the last option)
Start taking steps to make database structure proper. Make an extra table and fill it with split values.
Then you can use proper queries to select the data you need. Both you and next developer will have less troubles with this project in the future, not mentioning queries speed gain.
I am not sure why i cannot write a comment, but maybe you can try this:
SELECT name, category FROM companies WHERE category LIKE '$search%' or LOCATE('search', category)>0;
That would look if in category appears any of your 'search' value.
I would have to agree that you should make the database right. It'll save you much trouble and time later. However, using SELECT DISTINCT may fix your immediate issue.
I am a field service technician and I have an inventory of parts that is either issued to me by the company I work for or through orders for specific jobs. I am trying to design a website to manage my parts, both on-hand inventory and parts that have been returned or transferred to someone else. Here is the information I need to track:
part number(10 digit)
req number(8 digit, unique)
description(up to 50 characters)
location(Van or shed).
WorkOrder("w"+9 digits ex: 'W212141234')
BOL(15 digit bill of lading #)
TransferDate(date I get rid of part)
TransferMethod(enum 'DEF','RTS','OBF')
I will probably use PHP to make a website and interact with the MySQL database.
What is the best design? A multi-table approach or one table with webpages that display queries of only certain fields? I need a list of on hand parts that list part number, req number, description, and location. I will also need to be able to have "defective returns" view that will list what parts I returned as DEF with all the remaining fields filled in.
Besides the "on hand" fields, the rest of the fields won't have data until they are no longer "on hand".
I really appreciate any help because I am new to both SQL and PHP. I have experimented with Ruby on Rails and django but I am not sure if I need to tackle all that at this point.
Even though you give some information on your issue, it is hard to actually approach it as the question itself on "what is the best design" is vague.
What I would do is this:
MYSQL TABLE DESIGN
Table parts
req number(int(8), unique, KEY)
part number(int(10))
description(varchar(50))
location(enum 'Van','shed')
WorkOrder(varchar(10))
BOL(varchar(15))
TransferDate(date)
TransferMethod(enum 'DEF','RTS','OBF')
onhand (boolean)
PHP SCRIPTS
and then i would make 2 php scripts with a single query each and a table displaying the info
onhand.php
select *fields filled for on hand parts* from parts where onhand = 1
notonhand.php
select *fields filled for not on hand parts* from parts where onhand = 0
I am trying to create a script that finds a matching percentage between my table rows. For example my mySQL database in the table products contains the field name (indexed, FULLTEXT) with values like
LG 50PK350 PLASMA TV 50" Plasma TV Full HD 600Hz
LG TV 50PK350 PLASMA 50"
LG S24AW 24000 BTU
Aircondition LG S24AW 24000 BTU Inverter
As you may see all of them have some same keyword. But the 1st name and 2nd name are more similar. Additionally, 3rd and 4th have more similar keywords between them than 1st and 2nd.
My mySQL DB has thousands of product names. What I want is to find those names that have more than a percentage (let's say 60%) of similarity.
For example, as I said, 1st, 2nd (and any other name) that match between them with more than 60%, will be echoed in a group-style-format to let me know that those products are similar. 3rd and 4th and any other with more than 60% matching will be echoed after in another group, telling me that those products match.
If it is possible, it would be great to echo the keywords that satisfy all the grouped matching names. For example LG S24AW 24000 BTU is the keyword that is contained in 3rd and 4th name.
At the end I will create a list of all those keywords.
What I have now is the following query (as Jitamaro suggested)
Select t1.name, t2.name From products t1, products t2
that creates a new name field next to all other names. Excuse me that I don't know how to explain it right but this is what it does: (The real values are product names like above)
Before the query
-name-
A
B
C
D
E
After the query
-name- -name-
A A
B A
C A
D A
E A
A B
B B
C B
D B
E B
.
.
.
Is there a way either with mySQL or PHP that will find me the matching names and extract the keywords as I described above? Please share code examples.
Thank you community.
Query the DB with LIKE OR REGEXP:
SELECT * FROM product WHERE product_name LIKE '%LG%';
SELECT * FROM product WHERE product_name REGEXP "LG";
Loop the results and use similar_text():
$a = "LG 50PK350 PLASMA TV 50\" Plasma TV Full HD 600Hz"; // DB value
$b = "LG TV 50PK350 PLASMA 50\"" ; // USER QUERY
$i = similar_text($a, $b, $p);
echo("Matched: $i Percentage: $p%");
//outputs: Matched: 21 Percentage: 58.3333333333%
Your second example matches 62.0689655172%:
$a = "LG S24AW 24000 BTU"; // DB value
$b = "Aircondition LG S24AW 24000 BTU Inverter" ; // USER QUERY
$i = similar_text($a, $b, $p);
echo("Matched: $i Percentage: $p%");
You can define a percentage higher than, lets say, 40%, to match products.
Please note that similar_text() is case SensItivE so you should lower case the string.
As for your second question, the levenshtein() function (in MySQL) would be a good candidate.
When I look at your examples, I consider how I would try to find similar products based on the title. From your two examples, I can see one thing in each line that stands out above anything else: the model numbers. 50PK350 probably doesn't show up anywhere other than as related to this one model.
Now, MySQL itself isn't designed to deal with questions like this, but some bolt-on tools above it are. Part of the problem is that querying across all those fields in all positions is expensive. You really want to split it up a certain way and index that. The similarity class of Lucene will grant a high score to words that rarely appear across all data, but do appear as a high percentage of your data. See High level explanation of Similarity Class for Lucene?
You should also look at Comparison of full text search engine - Lucene, Sphinx, Postgresql, MySQL?
Scoring each word against the Lucene similarity class ought to be faster and more reliable. The sum of your scores should give you the most related products. For the TV, I'd expect to see exact matches first, then some others of the same size, then brand, then TVs in general, etc.
Whatever you do, realize that unless you alter the data structures by using another tool on top of the SQL system to create better data structures, your queries will be too slow and expensive. I think Lucene is probably the way to go. Sphinx or other options not mentioned may also be up for consideration.
This is trickier than it seems and there is information missing in your post:
How are people going to use this auto-complete function?
Is it relevant that you can find all names for a product? Because apparently not all stores name their products similarly so a clerk might not be able to find the product (s)he found.
Do you have information about which product names are for the same product?
Is it relevant from which store you're searching? where is this auto-complete used?
Should the auto-complete really only suggest products that match all the words you typed? (it's not so hard, technically, to correct typos)
I think you need a more clear picture of what you (or better yet: the users) want this auto-complete function to do.
An auto-complete function is very much a user-friendly type feature. It aids the user, possibly in a fuzzy way so there is no single right answer. You have to figure out what works best, not what is easiest to do technically.
First figure out what you want, then worry about technology.
One possible solution is to use Damerau-Levenstein distance. It could be used like this
select *
from products p
where DamerauLevenstein(p.name, '*user input here*')<=*X*
You'll have to figure out X that suites your needs best. It should be integer greater than zero. You could have it hard-coded, parameterized or calculated as needed.
The trickiest thing here is DamerauLevenstein. It has to be stored procedure, that implements Damerau-Levenstein algorithm. I don't have MySQL here, so I might write it for you later this day.
Update: MySQL does not support arrays in stored procedures, so there is no way to implement Damerau-Levenstein in MySQL, except using temporary table for each function call. And that will result in terrible performance. So you have two options: loop through the results in PHP with levenstein like Alix Axel suggests, or migrate your database to PostgreSQL, where arrays are supported.
There is also an option to create User-Defined function, but this requires writing this function in C, linking it to MySQL and possibly rebuilding MySQL, so this way you'll just add more headache.
Your approach seems sound. For matching similar products, I would suggest a trigram search. There's a pretty decent explanation of how this works along with the String::Trigram Perl module.
I would suggest using trigram search to get a list of matches, perhaps coupled with some manual review depending on how much data you have to deal with and how frequent you need to add new products. I've found this approach to work quite well in practice.
Maybe you want to find the longest common substring from the 2 strings? Then you need to compute a suffix tree for each of your strings see here http://en.wikipedia.org/wiki/Longest_common_substring_problem.
If you want to check all names against each other you need a cross join in mysql. There are many ways to achieve this:
1. Select a, b From t1, t2
2. Select a, b From t1 Join t2
3. Select a, b From t1 Cross Join t2
Then you can loop through the result. This is the same when I say create a 2d array with n^2-(n-1) elements and each element is connected with each other.
P.S.: Select t1.name, t2.name From products t1, products t2
It sounds like you've gone through all this trouble to explain a complex scenario, then said that you want to ignore the optimal answers and just get us to give you the "handshake" protocol (everything is compared to everything that hasn't been compared to it yet). So... pseudocode:
select * from table order by id
while (result) {
select * from table where id > result_id
}
That will do it.
If your database simply had a UPC code as one of it's fields, and this field was well-maintained, i.e., you could trust that it was entered correctly by the database maintainer and correctly reflected what the item was -- then you wouldn't need to do all of the work you suggest.
An even better idea might be to have a UPC field in your next database -- and constrain it as unique.
Database users attempt to put an-already-existing UPC into the database -- they get an error.
Database maintains its integrity.
And if such a database maintained its integrity -- the necessity of doing what you suggest never arises.
This probably doesn't help much with your current task (apologies) -- but for a future similar database -- you might wish to think about it...
I`d advise you to use some fulltext search engine, like sphinx. It has possibilities to implement any algorithm you want. For example, you may use "quorom" or "any" searches.
It seems that you might always want to return the shortest string?? That's more or a question than anything. But then you might have something like...
SELECT * FROM products LIMIT 1
WHERE product_name like '%LG%'
ORDER BY LENGTH(product_name) ASC
This is a clustering problem, which can be resolved by a data mining method. ( http://en.wikipedia.org/wiki/Cluster_analysis) It requires a lot of memory and computation intensive operations which is not suitable for database engine. Otherwise, separate data mining, text mining, or business analytics software wouldn't have existed.
This question is similar :) to this one:
What is the best way to implement a substring search in SQL?
Trigram can easily find similar rows, and in that question i posted a php+mysql+trigram solution.
You can use LIKE to find similar product names within the table. For example:
SELECT * FROM product WHERE product_name LIKE 'LG%';
Here is another idea (but I'm voting for levenshtein()):
Create a temporary table of all words used in names and their frequencies.
Choose range of results (most popular words are probably words like LCD or LED, most unique words could be good, they might be product actual names).
Suggest for each of result words either:
results with those words
results containing longest substring (like this: http://forums.mysql.com/read.php?10,277997,278020#msg-278020 ) of those words.
Ok, I think I was trying to implement very much similar thing. It can work the same as the google chrome address box. When you type the address it gives you the suggestions. This is what you are trying to achieve as far I am concerned.
I cannot give you exact solution to that but some advice.
You need to implement the dropdown box where someone starts to enter the product they are looking for
Then you need to get the current value of the dropdown and then run query like guy posted above. Can be "SELECT * FROM product WHERE product_name LIKE 'LG%';"
Save results of the query
Refresh the page
Add the results of the query to the dropdown
Note:
You need to save the query results somewhere like the text file with the HTML code i.e. "option" LG TS 600"/option" (add <> brackets to option of course). This values will be used for populating your option box after the page refresh. You need to set up the users session for the user to get the same results for the same user, otherwise if more users would use the search at the same time it could clash. So, with the search id and session id you can match them then. You can save it in the file or the table. Table would be more convenient. It is actually in my sense the whole subsystem for that what are you looking for.
I hope it helps.