sssql-optional-branch-pruning.md

title	SSSQL Optional Branch Pruning MVP
outline	deep

SSSQL Optional Branch Pruning MVP

This note documents the intentionally narrow first pass for truthful optional-condition pruning.

Supported syntax shapes

The MVP only inspects top-level AND terms under a query block's WHERE clause. One outer set of parentheses is tolerated around each branch.

Supported branch forms:

(:p IS NULL OR t.col = :p)

(:p IS NULL OR EXISTS (... :p ...))

(:p IS NULL OR NOT EXISTS (... :p ...))

Scalar predicates currently accept the comparison and match operators handled by the matcher. EXISTS / NOT EXISTS branches are only eligible when the subquery references the same parameter and no additional parameters appear in that branch.

Unsupported syntax shapes

The MVP is exact no-op for any branch that is not a direct top-level AND term, including:

• nested boolean rewrites
• mixed OR chains with more than one meaningful branch
• ambiguous guard shapes
• branches that rely on extra parameters
• general boolean simplification outside the targeted branch forms

Opt-in parameter targeting

Pruning is explicit opt-in. Only parameter names listed in optionalConditionParameters (or passed directly to pruneOptionalConditionBranches) are eligible. Parameters that are not listed remain exact no-op, even if the SQL shape itself is supported.

Known-absent definition

For explicitly targeted parameters, the MVP treats null and undefined as absent-equivalent. Any other value keeps the branch active, and the MVP does not simplify the known-present branch.

No-op policy

Only supported branches with an explicitly targeted absent-equivalent parameter are normalized away. Known-present branches remain unchanged. Unsupported or ambiguous shapes remain byte-for-byte intent no-op at the AST level, aside from formatter normalization when SQL is printed.