Edits for pre-compile regex(faster-compile)

[theonlychant]

Link to Issue or Description of Change

1. Link to an existing issue (if applicable):

-- N/A

2. Or, if no issue exists, describe the change:

Problem:
Several hot-path functions in ADK recompile regex patterns on every invocation instead of compiling once. Additionally, multiple dict iteration patterns use .keys() with separate value lookups instead of .items(), causing redundant hash lookups.

• models/registry.py - re.compile(regex).fullmatch(model) called inside the resolve() loop on every model resolution
• tools/_gemini_schema_util.py - 4 separate re.sub() calls in _to_snake_case() each recompiling their pattern
• models/gemma_llm.py - re.compile() for markdown code block parsing inside the function call extraction path
• memory/in_memory_memory_service.py - re.findall() recompiling on every call, plus set([...]) creating an unnecessary intermediate list
• sessions/_session_util.py, sessions/in_memory_session_service.py, sessions/database_session_service.py - .keys() + dict[key] instead of .items()

Solution:

• Pre-compile all regex patterns at module level so they are compiled once at import time
• Cache compiled regex in _compiled_regex_cache dict in the model registry, populated at registration time
• Replace set([...]) with set comprehension {...} to avoid intermediate list allocation
• Replace for key in dict.keys(): dict[key] with for key, value in dict.items() for single-pass iteration

These are all drop-in replacements with identical behavior -- no API or behavioral changes.

Testing Plan

Unit Tests:

• I have added or updated unit tests for my change.
• All unit tests pass locally.

-- No new tests needed. All changes are purely internal optimizations that preserve identical behavior. Existing tests in tests/unittests/models/, tests/unittests/sessions/, and tests/unittests/tools/ cover the modified functions.

Manual End-to-End (E2E) Tests:

-- Not applicable. These are micro-optimizations to existing internal code paths with no user-facing API changes.

Checklist

• I have read the CONTRIBUTING.md document.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have added tests that prove my fix is effective or that my feature works.
• New and existing unit tests pass locally with my changes.
• I have manually tested my changes end-to-end.
• Any dependent changes have been merged and published in downstream modules.

Additional context

Files changed (7):

• src/google/adk/models/registry.py -- Pre-compile regex at registration time into _compiled_regex_cache
• src/google/adk/tools/_gemini_schema_util.py -- 4 module-level compiled regex constants
• src/google/adk/models/gemma_llm.py -- Module-level _MARKDOWN_CODE_BLOCK_RE
• src/google/adk/memory/in_memory_memory_service.py -- Module-level _RE_WORDS + set comprehension
• src/google/adk/sessions/_session_util.py -- .items() iteration
• src/google/adk/sessions/in_memory_session_service.py -- .items() iteration
• src/google/adk/sessions/database_session_service.py -- .items() iteration

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[adk-bot]

Response from ADK Triaging Agent

Hello @1proprogrammerchant, thank you for your contribution!

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Thanks!

[rohityan]

is_gemini_31_live is defined twice and return statement has a typo

[rohityan]

This is not part of scope of this PR. Please create a separate PR for this.

[theonlychant]

ok I will create a new PR thanks for the heads-up by the way I'm sorry for any mess ups this is actually my first time committing code to google(I am doing this for experience)

[rohityan]

Hi @1proprogrammerchant , Thank you for your contribution! We appreciate you taking the time to submit this pull request.
Please address the review comments.