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java-topology/docs/tickets/mariadb-0002-setup-new-fields-find-item-quadratic.md
russell@unturf.com 9934133dcf whitepaper: 312 sites / 151 ecosystems — wave2+3 defect tables and PDF rebuild 
Add 88 new defect entries to HIGH and MEDIUM tables:
  HIGH: mysql-0001/0002, mariadb-0001, redis-0001/0002, valkey-0001/0002, openvpn-0001,
        vlc-0001, prometheus-0001, otel-collector-0001, cockroachdb-0001..0004,
        tidb-0001..0008, kubernetes-0001/0002, go-0001, kotlin-0002, scala-0001,
        allegro5-0001, sdl2-0001, grafana-0001, clickhouse-0001, duckdb-0001,
        mongodb-0001, envoy-0001, istio-0001, cilium-0001, linkerd2-0001,
        linux-0001/0002/0003, tor-0002/0003, curl-0001, julia-0001, lua-0001,
        perl5-0001, nats-0001, spring-0003/0004, tomcat-0001, onos-0002, odl-0002

  MEDIUM: helm-0001, mariadb-0002, openssl-0001/0002, memcached-0001,
          cassandra-0001..0004, flink-0001, storm-0001/0002, zookeeper-0001..0003,
          pip-0001, gradle-0001, nginx-0001, haproxy-0001, caddy-0001, varnish-0001,
          ffmpeg-0001, gstreamer-0001, raylib-0001, love2d-0001, php-0001/0002,
          r-source-0001, cpython-0002, ruby-0001, rabbitmq-0003/0004, activemq-0001,
          ovs-0001, onos-0003, odl-0002, jetty-0001

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2026-03-27 15:23:43 -04:00

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mariadb-0002 — setup_new_fields: O(N × S) find_item_in_list inside new-fields loop

Target: MariaDB/server Severity: MEDIUM CWE: CWE-407 (Inefficient Algorithmic Complexity) File: sql/sql_select.cc lines 29060–29064 Status: PATCHED

Defect

setup_new_fields() iterates a linked list of new_field ORDER objects (line 29060) and for each calls find_item_in_list(*new_field->item, fields, ...) (line 29062) — an O(S) linear scan over the SELECT list.

This gives O(N × S) complexity where N = length of the new-fields list and S = SELECT-list size. In multi-table UPDATE or INSERT ... SELECT with many computed columns, both N and S can reach the hundreds.

Root Cause

Same root cause as mariadb-0001: List<Item> has no hash index and find_item_in_list always walks from the head.

Fix

Build the same unordered_map<string, uint> name→position index that mariadb-0001's fix introduces for setup_order/setup_group, and reuse it in setup_new_fields. If the callers are separate, build the map locally at the top of setup_new_fields.

See: defects/mariadb/patch/mariadb-0002.patch

Benchmark

Covered by defects/mariadb/unit/MariadbTest.java — setup_new_fields quadratic test case.