[Subtask] Introduce query builder for composable graph filtering

[oxy86]

Overview

Introduce a query builder system that allows users to define complex filtering conditions using a structured interface instead of isolated dialogs.

This is the long-term UI and UX layer for the filtering system introduced in #215.

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Motivation

Current filtering mechanisms are:

• dialog-based
• single-condition
• not composable

Users need to express richer queries such as:

(type = "investor") AND (degree > 5) AND (weight ≥ 10)

This requires a unified and extensible query system.

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Scope

Phase 1 — Visual Query Builder (no-code)

• UI to define conditions:
  • attribute / metric selector
  • operator (=, >, <, etc.)
  • value input
• Support logical operators:
  • AND
  • OR

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Phase 2 — Internal Query Representation

• Define a query model (tree or expression-based)
• Reusable across:
  • filtering
  • subgraph extraction
  • future features

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Phase 3 — Optional DSL (advanced)

• Simple textual query language

Example:

degree > 5 AND type = "investor"

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Behavior

• Queries act on:
  • nodes
  • edges
• Results update graph visibility (non-destructive)

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UI Suggestions

• Dedicated "Filter / Query Panel"
• Ability to:
  • add/remove conditions
  • group conditions
  • preview results

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Implementation Notes

• Build on top of:
  • [Subtask] Unify and extend existing node filtering by structural metrics #216 Structural filtering
  • [Subtask] Filter nodes and edges by attributes (metadata-based filtering) #217 Attribute filtering
  • [Subtask] Unify node and edge filtering into a single filtering system #219 Unified filtering system
• Avoid duplicating logic already implemented in dialogs
• Query system should evaluate against current graph state

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Edge Cases

• Invalid queries
• Type mismatches (string vs numeric)
• Empty results

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Relation to Feature

Part of:
#215 Graph filtering, querying & subgraph extraction