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Arithmetic on an index key: the type mismatch names N where the service names a set of types #702
Description
What the service does
Measured against DynamoDB (us-east-1) on 2026-10-31 at 15:03 and 21:53 UTC, each request sent twice with identical answers, on a table with a GSI gsi_s on sidx (S). The item is r = {pk: r, n: N 5}.
- UpdateItem
SET sidx = :one + :one(sent at both times),SET sidx = n + :one(15:03) andSET sidx = :one - :one(21:53):ValidationException: One or more parameter values were invalid: Type mismatch for Index Key sidx Expected: S Actual: {N,HD,DOUBLE,FLOAT} IndexName: gsi_s, every time. - TransactWriteItems with the same Update as a member: cancellation reason
ValidationErrorwithOne or more parameter values were invalid: Type mismatch for Index Key sidx Expected: S Actual: {HD, N, DECIMAL, DOUBLE, INT, FLOAT} IndexName: gsi_sfor every arithmetic member at 15:03, andActual: {FLOAT, N, HD, DOUBLE, INT, DECIMAL}at 21:53. The six names are the same; their order changed between the two measurements.
What ExtendDB does
A SQLite server built from main (f49c5f823) answers every one of these with Actual: N, for example One or more parameter values were invalid: Type mismatch for Index Key sidx Expected: S Actual: N IndexName: gsi_s.
Proposed change
When the value written to an index key is an arithmetic expression, write the service's set in the Actual field: {N,HD,DOUBLE,FLOAT} on UpdateItem, and the six names in braces, {HD, N, DECIMAL, DOUBLE, INT, FLOAT}, in TransactWriteItems. A test of the TransactWriteItems text can compare the set of names, since the service's order varies.
Activity
LeeroyHannigan commentedon Nov 9, 2026
PartiQL UPDATE gives a third form of the set. Measured against DynamoDB (us-east-1) on 2026-11-09 at 11:45 UTC, each statement sent once, on a table with a GSI
gsi_sonsidx(S). Each statement wasUPDATE "<table>" SET ... WHERE pk = 'pqd-none', and that key holds no item:SET sidx = n + 1:ValidationException: One or more parameter values were invalid: Type mismatch for Index Key sidx Expected: S Actual: {N, FLOAT, INT, DOUBLE, HD} IndexName: gsi_sSET sidx = list_append(l, [1]): the same text withActual: LSET sidx = 5: the same text withActual: NSET sidx = '': the refusal of an empty string for a secondary index keySET sidx = 'x':ConditionalCheckFailedExceptionSo the service checks the value type before the condition of the missing item.
From the code, main answers the first two statements with the condition failure, because its PartiQL path does not type an arithmetic or
list_appendvalue. #853 types both, and its text for the arithmetic isActual: N.