Improve performance of mysql generator

[jupp0r]

This change improves performance for generating mysql models for databases with large number of tables by eliminating an N+1 query. In my local testing for a database with about 1000 tables and 140k columns, generation time was reduced from about 1h to less than one second.

This is on MySQL 5.7 (I know....), I think those original queries were faster on MySQL 8. The change is sensible in any case.

[codecov-commenter]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (61841dc) 90.54% compared to head (bffec36) 90.55%.

Files	Patch %	Lines
generator/mysql/query_set.go	92.85%	1 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##           master     #309      +/-   ##
==========================================
+ Coverage   90.54%   90.55%   +0.01%     
==========================================
  Files         124      124              
  Lines        7307     7288      -19     
==========================================
- Hits         6616     6600      -16     
+ Misses        530      528       -2     
+ Partials      161      160       -1     

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[go-jet]

Hi @jupp0r,

Whats your setup? Are you running MySQL 5.7 on a docker? Mac silicon?

generation time was reduced from about 1h to less than one second.

One minut or one second?

[jupp0r]

Hi @jupp0r,

Whats your setup? Are you running MySQL 5.7 on a docker? Mac silicon?

generation time was reduced from about 1h to less than one second.

One minut or one second?

One second. This is on an Apple M1 Max Macbook Pro running Percona 5.7.35-38 natively (the x64 version though, ie emulated using Rosetta. It's generally pretty performant compared to production on dev machines though). Each of the per-table queries was taking more than 30s for some reason. The single compound query is much faster. Might be an old mysql bug (missing index on the meta schema? lock contention? no idea why it was so slow). MySQL was saturating one core while doing those queries.

[go-jet]

Looks good. 👍