fix: EXPOSED-1071 Closing executed statements performance issue

[Oleg Babichev (obabichevjb)]

Description

Summary of the change: Close executed JDBC statements in reverse order to prevent quadratic transaction cleanup time when using HikariCP.

Detailed description:

• Why: JdbcTransaction previously closed executed statements in FIFO order. HikariCP tracks statements in a collection optimized for removal from the end, so closing a large number of accumulated statements in FIFO order caused repeated linear scans and resulted in quadratic cleanup time. This primarily affected databases reporting supportsMultipleResultSets = true, because Exposed retains their statements until transaction cleanup.

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Type of Change

• Bug fix

Affected databases:

• MariaDB
• Mysql5
• Mysql8
• Postgres
• SqlServer

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Related Issues

EXPOSED-1071 Closing executed statements performance issue

[Oleg Babichev (obabichevjb)]

This benchmark measures the time taken by JdbcTransaction.closeExecutedStatements() after preparing 200,000 statements in a single transaction. It compares statement cleanup before and after changing the closing order from FIFO to LIFO.

Database	Multiple result sets	Before	After	Before / after
PostgreSQL	Yes	12.835 s	27.759 ms	462.39×
MariaDB	Yes	12.842 s	19.833 ms	647.48×
MySQL 8	Yes	28.489 s	12.332 s	2.31×
MySQL 5	Yes	28.589 s	12.112 s	2.36×
SQLite	No	363.208 µs	418.917 µs	0.87×
Oracle	No	424.125 µs	367.458 µs	1.15×
H2 SQL Server mode	No	348.500 µs	414.000 µs	0.84×
H2 PostgreSQL mode	No	402.500 µs	369.208 µs	1.09×
H2 Oracle mode	No	371.125 µs	351.208 µs	1.06×
H2 MySQL mode	No	352.083 µs	370.917 µs	0.95×
H2 MariaDB mode	No	386.208 µs	337.625 µs	1.14×
H2	No	367.916 µs	382.250 µs	0.96×

• PostgreSQL cleanup decreased from 12.835 seconds to 27.759 milliseconds, a 462.39× improvement.
• MariaDB cleanup decreased from 12.842 seconds to 19.833 milliseconds, a 647.48× improvement.
• MySQL 5 and MySQL 8 improved by approximately 2.3×, although cleanup still took about 12 seconds.
• Results for databases without multiple-result-set support remained in the sub-millisecond range.