feat(stream): support nested event window sub-events

[JinqingKuang]

Description

Add recursive EVENT_WINDOW START WITH parsing, runtime conditionPath propagation, and _event_condition_path placeholder support.

Issue(s)

• Resolve: https://project.feishu.cn/taosdata_td/feature/detail/6952737120

Checklist

Please check the items in the checklist if applicable.

• Is the user manual updated?
• Are the test cases passed and automated?
• Is there no significant decrease in test coverage?

[gemini-code-assist]

Code Review

This pull request implements multi-level nested sub-event support for EVENT_WINDOW in stream processing. It introduces the _event_condition_path placeholder to identify matched nodes within a hierarchical start-condition tree and updates the notification payload to include conditionPath. The implementation includes changes to the parser, stream trigger task logic, and documentation. Feedback was provided regarding safer path length calculations and ensuring null-safety when evaluating event conditions.

[gemini-code-assist]

The loop for updating pResData does not check the null bitmap of tmpCol. If a condition evaluates to NULL, pTmpData[i] might contain an undefined value or 0. It is safer to explicitly check the null bitmap to ensure only non-null TRUE values are recorded as matches.

  for (int32_t i = 0; i < nrows; ++i) {
    if (pResData[i] == 0 && !colDataIsNull(&tmpCol, i) && pTmpData[i]) {
      pResData[i] = nodeId + 1;
    }
  }

[Copilot]

Pull request overview

This PR extends TDengine stream EVENT_WINDOW support to allow recursively nested START WITH groups, propagates a stable runtime “conditionPath” for matched nodes, and exposes that path via the new _event_condition_path placeholder and updated notification payload fields.

Changes:

• Parser: add recursive START WITH grammar (start_event_item) and validation for _event_condition_path usage.
• Runtime: build/start-condition metadata (node ids + stable paths), evaluate nested start trees, and propagate conditionPath through trigger calc params and notifications.
• Function/Scalar plumbing: register _event_condition_path as a pseudo/placeholder function and populate its value at execution time; add tests and docs.

Reviewed changes

Copilot reviewed 19 out of 19 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
test/cases/18-StreamProcessing/03-TriggerMode/test_event_new.py	Adds a system test verifying nested start groups produce expected _event_condition_path values.
source/libs/scalar/src/scalar.c	Populates _event_condition_path placeholder results via new varstring setters.
source/libs/parser/test/parStreamTest.cpp	Adds parser tests for nested start condition AST shape and placeholder legality.
source/libs/parser/src/parTranslater.c	Tracks placeholder bitmap and enforces _event_condition_path validity for event windows with sub-events.
source/libs/parser/src/parTokenizer.c	Adds keyword mapping for _EVENT_CONDITION_PATH.
source/libs/parser/inc/sql.y	Introduces recursive start_event_item grammar and _event_condition_path pseudo column.
source/libs/new-stream/src/streamUtil.c	Updates event notification payload to include conditionPath + conditionIndex and removes windowIndex.
source/libs/new-stream/src/streamTriggerTask.c	Implements nested start-condition evaluation, path switching, and conditionPath propagation into calc params/notifications.
source/libs/new-stream/inc/streamTriggerTask.h	Extends window structs with eventNodeId and adds start-condition meta structures.
source/libs/new-stream/inc/streamInt.h	Updates streamBuildEventNotifyContent signature to accept conditionPath.
source/libs/function/src/functionMgt.c	Exposes conditionPath as a stream pseudo value and wires placeholder parameter updates.
source/libs/function/src/builtins.c	Registers _event_condition_path builtin and its return type handling.
source/common/src/msg/streamMsg.c	Serializes/deserializes conditionPath in SSTriggerCalcParam and frees it in destructor.
include/libs/function/functionMgt.h	Adds FUNCTION_TYPE_EVENT_CONDITION_PATH.
include/common/streamMsg.h	Adds placeholder bit + conditionPath field to trigger calc param struct.
docs/zh/06-advanced/03-stream.md	Documents nested start_event_item and _event_condition_path (ZH advanced).
docs/zh/14-reference/03-taos-sql/41-stream.md	Updates syntax/semantics and notification JSON fields (ZH reference).
docs/en/06-advanced/03-stream.md	Documents nested start_event_item and _event_condition_path (EN advanced).
docs/en/14-reference/03-taos-sql/41-stream.md	Updates syntax/semantics and notification JSON fields (EN reference).

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[Copilot]

stTriggerTaskGetEventPathNodeIds defines a _exit: label that is never jumped to. With common -Wall/-Werror settings this triggers an -Wunused-label build failure. Remove the label (and the dead cleanup block), or refactor the early returns to goto _exit so the label is actually used.

Suggested change

	_exit:
	if (code != TSDB_CODE_SUCCESS) {
	taosMemoryFreeClear(pIds);
	}
	return code;

[Copilot]

Pull request overview

Copilot reviewed 21 out of 21 changed files in this pull request and generated 3 comments.

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[Copilot]

ASFLAGS is set to -Wa,--noexecstack unconditionally. That flag is ELF/GNU-as specific and can fail on toolchains where the assembler doesn’t recognize --noexecstack (e.g., macOS/clang-as, some cross toolchains). Consider gating this flag by platform/toolchain (e.g., only Linux/FreeBSD with GNU assembler), or probing support before adding it, to avoid breaking non-Linux builds.

[Copilot]

ASFLAGS := -Wa,--noexecstack is applied globally. --noexecstack is not universally supported by all assemblers/platforms; applying it unconditionally can break builds on non-ELF targets. Consider conditioning this flag on platforms where it’s supported (e.g., Linux/FreeBSD + GNU as), or appending it only when the assembler is known to accept it.

[Copilot]

startCondHasSubEvents is set via stTriggerTaskHasNestedEventStartCond(...), which only returns true for nested start-condition trees (i.e., a list containing another list), not for the existing single-level sub-event form (cond1, cond2, ...). Renaming this field to something like startCondHasNestedSubEvents (or similar) would better reflect its actual meaning and reduce the risk of misuse in future changes.

Suggested change

	bool startCondHasSubEvents;
	bool startCondHasNestedSubEvents;