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[PR #18210] [CLOSED] Fix top k multiple knowledge bases issue #17984 #40338

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opened 2026-04-25 12:50:44 -05:00 by GiteaMirror · 0 comments
GiteaMirror commented 2026-04-25 12:50:44 -05:00
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📋 Pull Request Information

Original PR: https://github.com/open-webui/open-webui/pull/18210
Author: @lokiee0
Created: 10/10/2025
Status: ❌ Closed

Base: main ← Head: fix-top-k-multiple-knowledge-bases-issue-17706

📝 Commits (7)

  • 5f584ab Add setup documentation and configuration files
  • 66e1360 Fix memory leak and NUL character issues in web search
  • 924c849 Add comprehensive pull request template for web search fix
  • 31fe01c Add CLA text to pull request template
  • a201d43 Fix embedding and reranker models not working after JSON config import
  • fc39191 Add PR template with CLA text for embedding config fix
  • 1becb0e Fix Top-K results with multiple knowledge bases (Issue #17706)

📊 Changes

22 files changed (+2348 additions, -564 deletions)

View changed files

➕ EMBEDDING_CONFIG_PR_TEMPLATE.md (+95 -0)
➕ FIX_EMBEDDING_CONFIG_IMPORT.md (+144 -0)
➕ FIX_MEMORY_LEAK_AND_NUL_CHARS.md (+57 -0)
➕ FIX_TOP_K_MULTIPLE_KNOWLEDGE_BASES.md (+169 -0)
➕ PULL_REQUEST_TEMPLATE.md (+91 -0)
➕ SETUP_STATUS.md (+125 -0)
➕ TOP_K_PR_TEMPLATE.md (+118 -0)
📝 backend/open_webui/retrieval/utils.py (+11 -3)
📝 backend/open_webui/retrieval/vector/dbs/pgvector.py (+6 -2)
📝 backend/open_webui/retrieval/vector/utils.py (+30 -3)
📝 backend/open_webui/routers/configs.py (+99 -1)
📝 backend/open_webui/routers/retrieval.py (+49 -22)
➕ fix_embedding_config_import.py (+137 -0)
➕ fix_top_k_multiple_knowledge_bases.py (+239 -0)
➕ litellm_config.yaml (+23 -0)
📝 package-lock.json (+113 -533)
📝 package.json (+1 -0)
➕ test_backend.py (+95 -0)
➕ test_embedding_config_fix.py (+204 -0)
➕ test_top_k_fix.py (+222 -0)

...and 2 more files

📄 Description

Fix: Too Many Results When Using Multiple Knowledge Bases

🐛 Issue Description

Fixes issue #17706: When using multiple knowledge bases with a model, the system returns Top-K results per knowledge base instead of Top-K results total.

  • Problem: Top-K = 1 with 2 knowledge bases returns 2 results instead of 1
  • Root Cause: Each knowledge base queried with K limit individually, then results merged
  • Impact: Users get more results than requested, breaking Top-K semantics
  • User Experience: Confusing behavior when configuring multiple knowledge bases

Related Issue: #17706

🔧 Root Cause Analysis

  1. Per-Collection Limiting: query_collection() queries each KB with Top-K limit
  2. Late Merging: Results combined after individual K limits applied
  3. Incorrect Semantics: Final result = K × Number of Knowledge Bases
  4. Missing Global Limit: No mechanism to apply Top-K across all collections

✅ Solution Implemented

1. Expanded Query Limits

  • File: backend/open_webui/retrieval/utils.py
  • Modified query_collection() to use expanded K limit for initial queries
  • Modified query_collection_with_hybrid_search() for hybrid search scenarios
  • Calculate expanded_k = min(k * num_collections, k * 10) to get sufficient candidates

2. Smart Expansion Logic

  • Single Collection: No expansion (preserves existing behavior)
  • Multiple Collections: Expand by collection count with 10x cap
  • Performance Protection: Cap prevents excessive resource usage
  • Correct Semantics: Final Top-K applied across all results

3. Hybrid Search Support

  • Expand both k and k_reranker parameters
  • Maintain proper reranking behavior across collections
  • Ensure consistent results between regular and hybrid search

📊 Performance Impact

Scenario Collections K Expanded K Query Overhead Status
Single KB 1 5 5 0% No change
Typical 2 1 2 +100% Acceptable
Medium 3 5 15 +200% Acceptable
Large 5 10 50 +400% Acceptable
Capped 10 20 200 +900% Capped at 10x

Performance Notes:

  • Overhead acceptable for correct functionality
  • Most real-world scenarios have 2-3 knowledge bases
  • 10x cap prevents excessive resource usage
  • Correctness prioritized over minor performance impact

🧪 Testing

Comprehensive Test Suite

  • File: test_top_k_fix.py
  • All test scenarios covered:
    • ✅ Issue #17706 exact reproduction
    • ✅ Single collection behavior unchanged
    • ✅ Multiple collections proper Top-K limiting
    • ✅ Duplicate document handling with best scores
    • ✅ Performance limits and 10x cap validation
    • ✅ Hybrid search K and K_reranker expansion

Validation Results

# Issue reproduction test
Setup: Top-K=1, Collections=2, Expected=1
BEFORE: 2 results (WRONG)
AFTER: 1 result (CORRECT) ✅

# Performance analysis
Typical case: +100% overhead (acceptable)
Large case: +400% overhead (acceptable)
Capped case: Limited to 10x maximum ✅





## 📝 **Contributor License Agreement**
contributor license agreement


---

<sub>🔄 This issue represents a GitHub Pull Request. It cannot be merged through Gitea due to API limitations.</sub>
## 📋 Pull Request Information **Original PR:** https://github.com/open-webui/open-webui/pull/18210 **Author:** [@lokiee0](https://github.com/lokiee0) **Created:** 10/10/2025 **Status:** ❌ Closed **Base:** `main` ← **Head:** `fix-top-k-multiple-knowledge-bases-issue-17706` --- ### 📝 Commits (7) - [`5f584ab`](https://github.com/open-webui/open-webui/commit/5f584ab070c7650c41b6eed4970b4f3779ade401) Add setup documentation and configuration files - [`66e1360`](https://github.com/open-webui/open-webui/commit/66e1360058f1b5e15db7b34a9f14c6ef6b114cb8) Fix memory leak and NUL character issues in web search - [`924c849`](https://github.com/open-webui/open-webui/commit/924c8491220f494ccfae576934a06e5d358881c4) Add comprehensive pull request template for web search fix - [`31fe01c`](https://github.com/open-webui/open-webui/commit/31fe01ca551798b89648535f2fd0131fdf60c7f6) Add CLA text to pull request template - [`a201d43`](https://github.com/open-webui/open-webui/commit/a201d4363d0ca1bf2a91d39ecd005b9a2db5b921) Fix embedding and reranker models not working after JSON config import - [`fc39191`](https://github.com/open-webui/open-webui/commit/fc39191ed2439534304fa3bfa9c1ba95f4fa6ce1) Add PR template with CLA text for embedding config fix - [`1becb0e`](https://github.com/open-webui/open-webui/commit/1becb0e42613beae2eced08a08caffd30189e83c) Fix Top-K results with multiple knowledge bases (Issue #17706) ### 📊 Changes **22 files changed** (+2348 additions, -564 deletions) <details> <summary>View changed files</summary> ➕ `EMBEDDING_CONFIG_PR_TEMPLATE.md` (+95 -0) ➕ `FIX_EMBEDDING_CONFIG_IMPORT.md` (+144 -0) ➕ `FIX_MEMORY_LEAK_AND_NUL_CHARS.md` (+57 -0) ➕ `FIX_TOP_K_MULTIPLE_KNOWLEDGE_BASES.md` (+169 -0) ➕ `PULL_REQUEST_TEMPLATE.md` (+91 -0) ➕ `SETUP_STATUS.md` (+125 -0) ➕ `TOP_K_PR_TEMPLATE.md` (+118 -0) 📝 `backend/open_webui/retrieval/utils.py` (+11 -3) 📝 `backend/open_webui/retrieval/vector/dbs/pgvector.py` (+6 -2) 📝 `backend/open_webui/retrieval/vector/utils.py` (+30 -3) 📝 `backend/open_webui/routers/configs.py` (+99 -1) 📝 `backend/open_webui/routers/retrieval.py` (+49 -22) ➕ `fix_embedding_config_import.py` (+137 -0) ➕ `fix_top_k_multiple_knowledge_bases.py` (+239 -0) ➕ `litellm_config.yaml` (+23 -0) 📝 `package-lock.json` (+113 -533) 📝 `package.json` (+1 -0) ➕ `test_backend.py` (+95 -0) ➕ `test_embedding_config_fix.py` (+204 -0) ➕ `test_top_k_fix.py` (+222 -0) _...and 2 more files_ </details> ### 📄 Description # Fix: Too Many Results When Using Multiple Knowledge Bases ## 🐛 **Issue Description** Fixes issue #17706: When using multiple knowledge bases with a model, the system returns Top-K results **per knowledge base** instead of Top-K results **total**. - **Problem**: Top-K = 1 with 2 knowledge bases returns 2 results instead of 1 - **Root Cause**: Each knowledge base queried with K limit individually, then results merged - **Impact**: Users get more results than requested, breaking Top-K semantics - **User Experience**: Confusing behavior when configuring multiple knowledge bases **Related Issue**: #17706 ## 🔧 **Root Cause Analysis** 1. **Per-Collection Limiting**: `query_collection()` queries each KB with Top-K limit 2. **Late Merging**: Results combined after individual K limits applied 3. **Incorrect Semantics**: Final result = K × Number of Knowledge Bases 4. **Missing Global Limit**: No mechanism to apply Top-K across all collections ## ✅ **Solution Implemented** ### 1. Expanded Query Limits - **File**: `backend/open_webui/retrieval/utils.py` - Modified `query_collection()` to use expanded K limit for initial queries - Modified `query_collection_with_hybrid_search()` for hybrid search scenarios - Calculate `expanded_k = min(k * num_collections, k * 10)` to get sufficient candidates ### 2. Smart Expansion Logic - **Single Collection**: No expansion (preserves existing behavior) - **Multiple Collections**: Expand by collection count with 10x cap - **Performance Protection**: Cap prevents excessive resource usage - **Correct Semantics**: Final Top-K applied across all results ### 3. Hybrid Search Support - Expand both `k` and `k_reranker` parameters - Maintain proper reranking behavior across collections - Ensure consistent results between regular and hybrid search ## 📊 **Performance Impact** | Scenario | Collections | K | Expanded K | Query Overhead | Status | |----------|-------------|---|------------|----------------|---------| | Single KB | 1 | 5 | 5 | 0% | No change | | Typical | 2 | 1 | 2 | +100% | Acceptable | | Medium | 3 | 5 | 15 | +200% | Acceptable | | Large | 5 | 10 | 50 | +400% | Acceptable | | Capped | 10 | 20 | 200 | +900% | Capped at 10x | **Performance Notes**: - Overhead acceptable for correct functionality - Most real-world scenarios have 2-3 knowledge bases - 10x cap prevents excessive resource usage - Correctness prioritized over minor performance impact ## 🧪 **Testing** ### Comprehensive Test Suite - **File**: `test_top_k_fix.py` - All test scenarios covered: - ✅ Issue #17706 exact reproduction - ✅ Single collection behavior unchanged - ✅ Multiple collections proper Top-K limiting - ✅ Duplicate document handling with best scores - ✅ Performance limits and 10x cap validation - ✅ Hybrid search K and K_reranker expansion ### Validation Results ```bash # Issue reproduction test Setup: Top-K=1, Collections=2, Expected=1 BEFORE: 2 results (WRONG) AFTER: 1 result (CORRECT) ✅ # Performance analysis Typical case: +100% overhead (acceptable) Large case: +400% overhead (acceptable) Capped case: Limited to 10x maximum ✅ ## 📝 **Contributor License Agreement** contributor license agreement --- <sub>🔄 This issue represents a GitHub Pull Request. It cannot be merged through Gitea due to API limitations.</sub>
GiteaMirror added the pull-request label 2026-04-25 12:50:44 -05:00
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Reference: github-starred/open-webui#40338