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Query errors

This page gives a brief overview of errors returned by the server when running queries.

Syntax errors

The output similar to the following is produced when a syntax error is encountered.

[TQL03] TypeQL Error: There is a syntax error at 2:15:
    define
-->   created sub attribute, value datetime;
    ~~~~~~~~~~~~~~^
      updated sub attribute, value datetime;
Expected TYPE.
Caused: Error in usage of TypeQL.
Caused: [TSV7] Query parsing failed.

Syntax errors never terminate transactions.

Validation errors

Most constraints, such as type capabilities and value constraints, are validated immediately as the data is inserted or deleted. To avoid entering incomplete state, the transaction is terminated and changes are lost.

Example validation error
[CNT6] Constraint '^user.$' has been violated: value '"Bob"' does not match the regex.
Caused: [DVL7] Constraint on attribute type 'username' was violated.
Caused: [COW5] Concept write failed due to a data validation error.
Caused: [WEX1] Write execution failed due to a concept write error.
Caused: [PEX6] Error executing write operation.
Caused: [QEX14] Error while execution write pipeline.

Some constraints, such as cardinality, are only validated when the data is committed. If an error is encountered during commit, the transaction is terminated and changes are lost.

Example commit error
[CNT5] Constraint '@card(1..2)' has been violated: found 0 instances.
Caused: [DVL11] Instance [1F00 0000 0000 0000 0000 00] of relation type 'friendship' has a relates constraint violation for role type 'friendship:friend'.
Caused: [COW5] Concept write failed due to a data validation error.
Caused: [DCT2] Data commit error.

Isolation errors

If two concurrent transaction modify the same data, the one that commits later may fail if the changes cannot be unambiguously resolved. The transaction is still terminated and all data is lost.

Example isolation error
[STC2] Commit in database 'test' failed with isolation conflict: Transaction uses a lock held by a concurrent commit.
Caused: [SST1] Snapshot commit failed due to storage commit error.
Caused: [DCT4] Snapshot error.
Caused: [TSV5] Data transaction commit failed.