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operations on ManyToMany relations - do not use subquery when not necessary + avoid ER_CANT_UPDATE_USED_TABLE_IN_SF_OR_TRG error on mysql #2406

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operations on ManyToMany relations - do not use subquery when not necessary + avoid ER_CANT_UPDATE_USED_TABLE_IN_SF_OR_TRG error on mysql #2406

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76 changes: 69 additions & 7 deletions lib/relations/manyToMany/ManyToManyModifyMixin.js
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Original file line number Diff line number Diff line change
@@ -1,6 +1,10 @@
'use strict';

const { ManyToManyFindOperation } = require('./find/ManyToManyFindOperation');
const { isMySql } = require('../../utils/knexUtils');

const FindByIdSelector = /^findByIds?$/;
const RelateUnrelateSelector = /relate$/;

// This mixin contains the shared code for all modify operations (update, delete, relate, unrelate)
// for ManyToManyRelation operations.
Expand All @@ -10,6 +14,8 @@ const { ManyToManyFindOperation } = require('./find/ManyToManyFindOperation');
// that we are able to `innerJoin` the join table to the query. Most SQL engines don't allow
// joins in updates or deletes. Join table is joined so that queries can reference the join
// table columns.
//
// If the subquery is not needed at all (e.g. the query has only a findById(s) operation - usually coming from graph upsert) - skip it
const ManyToManyModifyMixin = (Operation) => {
return class extends Operation {
constructor(...args) {
Expand All @@ -26,7 +32,7 @@ const ManyToManyModifyMixin = (Operation) => {
onBuild(builder) {
this.modifyFilterSubquery = this.createModifyFilterSubquery(builder);

if (this.modifyMainQuery) {
if (this.modifyMainQuery && this.modifyFilterSubquery) {
// We can now remove the where and join statements from the main query.
this.removeFiltersFromMainQuery(builder);

Expand All @@ -38,6 +44,22 @@ const ManyToManyModifyMixin = (Operation) => {
}

createModifyFilterSubquery(builder) {
// Check if the subquery is needed
// - it may not be, if there are no operations other than findById(s) on the main query
// and proceed only if passed builder operates on the joinTable
if (builder.modelClass() === this.relation.joinTableModelClass) {
const checkQuery = builder
.clone()
.toFindQuery()
.modify(this.relation.modify)
.clear(RelateUnrelateSelector)
.clear(FindByIdSelector)
.clearOrder();
if (checkQuery.isSelectAll()) {
return null;
}
}

const relatedModelClass = this.relation.relatedModelClass;
const builderClass = builder.constructor;

Expand Down Expand Up @@ -73,15 +95,55 @@ const ManyToManyModifyMixin = (Operation) => {
applyModifyFilterForJoinTable(builder) {
const joinTableOwnerRefs = this.relation.joinTableOwnerProp.refs(builder);
const joinTableRelatedRefs = this.relation.joinTableRelatedProp.refs(builder);

const relatedRefs = this.relation.relatedProp.refs(builder);
const ownerValues = this.owner.getProps(this.relation);

const subquery = this.modifyFilterSubquery.clone().select(relatedRefs);
if (this.modifyFilterSubquery) {
// if subquery is used (in a non-find query)
const relatedRefs = this.relation.relatedProp.refs(builder);
const subquery = this.modifyFilterSubquery.clone().select(relatedRefs);

if (isMySql(builder.knex())) {
// and only for mysql:
// extract the subquery selecting related ids to separate query run before the main query
// to avoid ER_CANT_UPDATE_USED_TABLE_IN_SF_OR_TRG mysql error
// when executing a db trigger on a join table which updates related table
//
// This workaround is only needed for MySQL.
// It could possibly be applied to all DBMS, if proven necessary,
// but others seem to handle such cases just fine.
//
// https://stackoverflow.com/a/2314264/3729316
// "MySQL triggers can't manipulate the table they are assigned to.
// All other major DBMS support this feature so hopefully MySQL will add this support soon."
// ~ Cory House, 2010
builder
.runBefore(() => subquery.execute())
.runBefore((related, builder) => {
if (!related.length) {
builder.resolve([]);
return;
}
builder.whereInComposite(
joinTableRelatedRefs,
related.map((m) => m.$values(this.relation.relatedProp.props))
);
});
} else {
builder.whereInComposite(joinTableRelatedRefs, subquery);
}
} else if (builder.parentQuery()) {
// if subquery is not used:
// rewrite findById(s) from related table to join table
builder.parentQuery().forEachOperation(FindByIdSelector, (op) => {
if (op.name === 'findByIds') {
builder.whereInComposite(joinTableRelatedRefs, op.ids);
} else {
builder.whereComposite(joinTableRelatedRefs, op.id);
}
});
}

return builder
.whereInComposite(joinTableRelatedRefs, subquery)
.whereInComposite(joinTableOwnerRefs, ownerValues);
return builder.whereInComposite(joinTableOwnerRefs, ownerValues);
}

toFindOperation() {
Expand Down