adding rewrite parameter docs

_query-dsl/rewrite-parameter.md

@@ -0,0 +1,174 @@
+---
+layout: default
+title: Rewrite
+nav_order: 80
+---
+
+# Rewrite
+
+Multi-term queries like `wildcard`, `prefix`, `regexp`, `fuzzy`, and `range` expand internally into sets of terms. The `rewrite` parameter allows you to control how these term expansions are executed and scored.
+
+When a multi-term query expands into many terms (for example `prefix: "error*"` matching hundreds of terms), they are converted into actual term queries internally. This process can:
+
+* Exceed the `indices.query.bool.max_clause_count` limit (default `1024`)
+* Affect how scores are calculated for matching documents
+* Impact memory and latency depending on the rewrite method used
+
+## Available rewrite methods
+
+| Rewrite method | Description |
+| [`constant_score`](#constant_score-default) | (Default) All expanded terms are evaluated together as a single unit, assigning the same score to every match. Efficient for filtering use cases. |
+| [`scoring_boolean`](#scoring_boolean) | Breaks the query into a Boolean `should` clause with one term query per match. Each result is scored individually based on relevance. |
+| [`constant_score_boolean`](#constant_score_boolean) | Similar to `scoring_boolean`, but all documents receive a fixed score regardless of term frequency. Maintains Boolean structure without TF/IDF weighting. |
+| [`top_terms_N`](#top_terms_N) | Restricts scoring and execution to the N most frequent terms. Reduces resource usage and prevents clause overload. |
+| [`top_terms_boost_N`](#top_terms_boost_N) | Like `top_terms_N`, but uses static boosting instead of full scoring. Offers performance improvements with simplified relevance. |
+| [`top_terms_blended_freqs_N`](#top_terms_blended_freqs_N) | Chooses the top N matching terms and averages their document frequencies for scoring. Produces balanced scores without full term explosion. |
+
+## Boolean-based rewrite limits
+
+All Boolean-based rewrites, such as `scoring_boolean`, `constant_score_boolean`, and `top_terms_*`, are subject to:
+
+```json
+indices.query.bool.max_clause_count
+```
+
+This setting controls the maximum number of allowed Boolean `should` clauses (default: 1024). If your query expands beyond this limit, it will be rejected with a `too_many_clauses` error.
+
+## constant_score (default)
+
+* Executes all term matches as a single bitset query.
+* Ignores scoring altogether; every document gets `_score = 1.0`.
+* Fastest option; ideal when filtering is the goal.
+
+```json
+POST /logs/_search
+{
+  "query": {
+    "wildcard": {
+      "message": {
+        "value": "warning*"
+      }
+    }
+  }
+}
+```
+{% include copy-curl.html %}
+
+## scoring_boolean
+
+* Expands the wildcard into individual `term` queries inside a Boolean `should` clause.
+* Each document’s score reflects how many terms it matches and their term frequency.
+* Can trigger `too_many_clauses` if many terms match.
+
+```json
+POST /logs/_search
+{
+  "query": {
+    "wildcard": {
+      "message": {
+        "value": "warning*",
+        "rewrite": "scoring_boolean"
+      }
+    }
+  }
+}
+```
+{% include copy-curl.html %}
+
+## constant_score_boolean
+
+* Similar structure to `scoring_boolean`, but documents are not ranked.
+* All matching docs receive the same score.
+* This retains Boolean clause flexibility (e.g., use with `must_not`) without ranking.
+
+```json
+POST /logs/_search
+{
+  "query": {
+    "wildcard": {
+      "message": {
+        "value": "warning*",
+        "rewrite": "constant_score_boolean"
+      }
+    }
+  }
+}
+```
+{% include copy-curl.html %}
+
+## top_terms_N
+
+* Only the N most frequent matching terms are selected and scored.
+* Useful when you expect large expansion and want to limit load.
+* Other valid terms are ignored to preserve performance.
+
+```json
+POST /logs/_search
+{
+  "query": {
+    "wildcard": {
+      "message": {
+        "value": "warning*",
+        "rewrite": "top_terms_2"
+      }
+    }
+  }
+}
+```
+{% include copy-curl.html %}
+
+## top_terms_boost_N
+
+* Limits expansion to the top N terms like `top_terms_N`.
+* Rather than computing TF/IDF, it assigns a pre-set boost per term.
+* Provides faster execution with predictable relevance weights.
+
+```json
+POST /logs/_search
+{
+  "query": {
+    "wildcard": {
+      "message": {
+        "value": "warning*",
+        "rewrite": "top_terms_boost_2"
+      }
+    }
+  }
+}
+```
+{% include copy-curl.html %}
+
+## top_terms_blended_freqs_N
+
+* Picks the top N matching terms and applies a blended frequency to all.
+* Blending makes scoring smoother across terms that differ in frequency.
+* Good tradeoff when you want performance with realistic scoring.
+
+```json
+POST /logs/_search
+{
+  "query": {
+    "wildcard": {
+      "message": {
+        "value": "warning*",
+        "rewrite": "top_terms_blended_freqs_2"
+      }
+    }
+  }
+}
+```
+{% include copy-curl.html %}
+
+## Summary
+
+The `rewrite` parameter gives you control over how multi-term queries behave under the hood.
+
+| Mode                        | Scores                                 | Performance | Notes                                         |
+| --------------------------- | -------------------------------------- | ----------- | --------------------------------------------- |
+| `constant_score`            | Same score for all matches             | Best        | Default mode, ideal for filters               |
+| `scoring_boolean`           | TF/IDF-based                           | Moderate    | Full relevance scoring                        |
+| `constant_score_boolean`    | Same score, but with Boolean structure | Moderate    | Use with `must_not` or `minimum_should_match` |
+| `top_terms_N`               | TF/IDF on top N terms                  | Efficient   | Truncates expansion                           |
+| `top_terms_boost_N`         | Static boosts                          | Fast        | Less accurate                                 |
+| `top_terms_blended_freqs_N` | Blended score                          | Balanced    | Best scoring/efficiency tradeoff              |
+