palashc opened a new pull request, #2468:
URL: https://github.com/apache/phoenix/pull/2468
### What changes were proposed in this pull request?
Adds the `$LIST_APPEND` operator to the BSON SET update-expression layer in
`UpdateExpressionUtils`. Inside a `$SET` block the new operator accepts:
```
{ "$SET": { "<path>": { "$LIST_APPEND": [<op1>, <op2>] } } }
```
Each operand resolves to a `BsonArray` via one of:
- a literal `BsonArray`
- a `BsonString` naming a top-level or nested document path (existing value
must be an array)
- a `{ "$IF_NOT_EXISTS": { "<path>": <fallback> } }` document whose resolved
value must be an array
The result is `op1 ⧺ op2` with order and duplicates preserved. The operator
slots in alongside the existing `$ADD` / `$SUBTRACT` / `$IF_NOT_EXISTS` cases
in `getNewFieldValue`; the resolved `BsonArray` is then written back via the
existing nested-path SET machinery, so no changes are required to
`updateNestedField`, `updateArrayAtLeafNode`, or `updateDocumentAtLeafNode`.
Nested `$LIST_APPEND` operands and arity ≠ 2 are explicitly rejected.
### Why are the changes needed?
The BSON update-expression engine today supports `$SET` / `$UNSET` / `$ADD`
/ `$DELETE_FROM_SET` / `$IF_NOT_EXISTS` / arithmetic `$ADD` / `$SUBTRACT`, but
has no primitive for appending to an existing list. Downstream services that
maintain append-only queues or event lists in a BSON column have to perform a
read-modify-write cycle today, which doesn't compose with the atomic
single-statement semantics the other operators already provide. This change
rounds out the list-valued update surface so an append (or create-or-append)
composes naturally with sibling `$ADD` / `$IF_NOT_EXISTS` clauses inside the
same `$SET` block.
### Does this PR introduce _any_ user-facing change?
Yes — a new optional operator `$LIST_APPEND` is accepted inside `$SET`. No
existing behavior changes: update expressions that did not use `$LIST_APPEND`
previously continue to be evaluated identically.
### How was this patch tested?
- 15 new unit tests in `UpdateExpressionUtilsTest` covering:
- all three accepted operand shapes (literal array, path string,
`$IF_NOT_EXISTS`),
- the canonical "create-or-append on a missing field" pattern via
`$IF_NOT_EXISTS` with an empty-array fallback,
- all rejection cases (missing path with no `$IF_NOT_EXISTS`, path to a
non-array, non-array `:placeholder`, `$IF_NOT_EXISTS` fallback that resolves to
a non-array, nested `$LIST_APPEND`, arity ≠ 2),
- result semantics (duplicates and order preserved, heterogeneous element
types, empty operands),
- nested document-path target (`nested.queue`),
- array-index target (`matrix[0]`),
- composition with a sibling `$ADD` in the same `$SET` block.
Runs in ~0.7s. `UpdateExpressionUtilsTest`: 23/23 pass (8 pre-existing +
15 new).
- 1 new end-to-end IT in `Bson2IT.testListAppendUpdateExpression` exercising
the full SQL → BSON wire pipeline via `BSON_UPDATE_EXPRESSION(...)` in `ON
DUPLICATE KEY UPDATE`. Two write-then-read phases on one row: a basic append to
an existing list, and a create-or-append using `$IF_NOT_EXISTS` composed with a
sibling `$ADD` on a numeric counter in the same `$SET`. 1/1 pass in ~57s on the
standard mini-cluster.
### Was this patch authored or co-authored using generative AI tooling?
Generated-by: Cursor (Claude Opus 4.7)
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