SequelizeForeignKeyConstraintError when requesting transaction quickly serveral times.

The error message following occurs when I request transaction ("/tx") quickly several times.

{ SequelizeForeignKeyConstraintError: update or delete on table "AssetSchemes" violates foreign key constraint "AssetTransferInputs_assetType_fkey" on table "AssetTransferInputs"
at Query.formatError (/home/kodebox/codechain/codechain-indexer/node_modules/sequelize/lib/dialects/postgres/query.js:296:16)
at query.catch.err (/home/kodebox/codechain/codechain-indexer/node_modules/sequelize/lib/dialects/postgres/query.js:86:18)
at tryCatcher (/home/kodebox/codechain/codechain-indexer/node_modules/sequelize/node_modules/bluebird/js/release/util.js:16:23)
at Promise._settlePromiseFromHandler (/home/kodebox/codechain/codechain-indexer/node_modules/sequelize/node_modules/bluebird/js/release/promise.js:512:31)
at Promise._settlePromise (/home/kodebox/codechain/codechain-indexer/node_modules/sequelize/node_modules/bluebird/js/release/promise.js:569:18)
at Promise._settlePromise0 (/home/kodebox/codechain/codechain-indexer/node_modules/sequelize/node_modules/bluebird/js/release/promise.js:614:10)
at Promise._settlePromises (/home/kodebox/codechain/codechain-indexer/node_modules/sequelize/node_modules/bluebird/js/release/promise.js:690:18)
at _drainQueueStep (/home/kodebox/codechain/codechain-indexer/node_modules/sequelize/node_modules/bluebird/js/release/async.js:138:12)
at _drainQueue (/home/kodebox/codechain/codechain-indexer/node_modules/sequelize/node_modules/bluebird/js/release/async.js:131:9)
at Async._drainQueues (/home/kodebox/codechain/codechain-indexer/node_modules/sequelize/node_modules/bluebird/js/release/async.js:147:5)
at Immediate.Async.drainQueues [as _onImmediate] (/home/kodebox/codechain/codechain-indexer/node_modules/sequelize/node_modules/bluebird/js/release/async.js:17:14)
at runCallback (timers.js:705:18)
at tryOnImmediate (timers.js:676:5)
at processImmediate (timers.js:658:5)
at process.topLevelDomainCallback (domain.js:120:23)
name: 'SequelizeForeignKeyConstraintError',
parent:
{ error: update or delete on table "AssetSchemes" violates foreign key constraint "AssetTransferInputs_assetType_fkey" on table "AssetTransferInputs"
at Connection.parseE (/home/kodebox/codechain/codechain-indexer/node_modules/pg/lib/connection.js:554:11)
at Connection.parseMessage (/home/kodebox/codechain/codechain-indexer/node_modules/pg/lib/connection.js:379:19)
at Socket. (/home/kodebox/codechain/codechain-indexer/node_modules/pg/lib/connection.js:119:22)
at Socket.emit (events.js:189:13)
at Socket.EventEmitter.emit (domain.js:441:20)
at addChunk (_stream_readable.js:284:12)
at readableAddChunk (_stream_readable.js:265:11)
at Socket.Readable.push (_stream_readable.js:220:10)
at TCP.onStreamRead [as onread] (internal/stream_base_commons.js:94:17)
name: 'error',
length: 388,
severity: 'ERROR',
code: '23503',
detail:
'Key (assetType)=(6ed1f013b0bad558266590f9f6a917058ffb4063) is still referenced from table "AssetTransferInputs".',
hint: undefined,
position: undefined,
internalPosition: undefined,
internalQuery: undefined,
where: undefined,
schema: 'public',
table: 'AssetTransferInputs',
column: undefined,
dataType: undefined,
constraint: 'AssetTransferInputs_assetType_fkey',
file: 'ri_triggers.c',
line: '3280',
routine: 'ri_ReportViolation',
sql: 'DELETE FROM "Blocks" WHERE "number" = 81' },
original:
{ error: update or delete on table "AssetSchemes" violates foreign key constraint "AssetTransferInputs_assetType_fkey" on table "AssetTransferInputs"
at Connection.parseE (/home/kodebox/codechain/codechain-indexer/node_modules/pg/lib/connection.js:554:11)
at Connection.parseMessage (/home/kodebox/codechain/codechain-indexer/node_modules/pg/lib/connection.js:379:19)
at Socket. (/home/kodebox/codechain/codechain-indexer/node_modules/pg/lib/connection.js:119:22)
at Socket.emit (events.js:189:13)
at Socket.EventEmitter.emit (domain.js:441:20)
at addChunk (_stream_readable.js:284:12)
at readableAddChunk (_stream_readable.js:265:11)
at Socket.Readable.push (_stream_readable.js:220:10)
at TCP.onStreamRead [as onread] (internal/stream_base_commons.js:94:17)
name: 'error',
length: 388,
severity: 'ERROR',
code: '23503',
detail:
'Key (assetType)=(6ed1f013b0bad558266590f9f6a917058ffb4063) is still referenced from table "AssetTransferInputs".',
hint: undefined,
position: undefined,
internalPosition: undefined,
internalQuery: undefined,
where: undefined,
schema: 'public',
table: 'AssetTransferInputs',
column: undefined,
dataType: undefined,
constraint: 'AssetTransferInputs_assetType_fkey',
file: 'ri_triggers.c',
line: '3280',
routine: 'ri_ReportViolation',
sql: 'DELETE FROM "Blocks" WHERE "number" = 81' },
sql: 'DELETE FROM "Blocks" WHERE "number" = 81',
fields: null,
table: 'AssetSchemes',
value: undefined,
index: 'AssetTransferInputs_assetType_fkey',
reltype: undefined }
(node:19211) UnhandledPromiseRejectionWarning: Error: DBError
at Object.exports.DBError (/home/kodebox/codechain/codechain-indexer/src/exception.ts:2:30)
at Object.deleteBlockByNumber (/home/kodebox/codechain/codechain-indexer/src/models/logic/block.ts:188:25)
(node:19211) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 2)
(node:19211) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.