Painless docs overhaul (troubleshooting)

troubleshoot/elasticsearch/painless-array-list-manipulation-errors.md

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+---
+navigation_title: Array manipulation errors
+applies_to:
+  stack: ga
+  serverless: ga
+products:
+  - id: elasticsearch
+---
+
+# Troubleshoot array manipulation errors in Painless
+
+Follow these guidelines to avoid array (list) access errors in your Painless scripts.
+
+An array `index_out_of_bounds_exception` occurs when a script tries to access an element at a position that does not exist in the array. For example, if an array has two elements, trying to access a third element triggers this exception. 
+
+## Sample error
+
+```json
+{
+  "error": {
+    "root_cause": [
+      {
+        "type": "index_out_of_bounds_exception",
+        "reason": "index_out_of_bounds_exception: Index 2 out of bounds for length 2"
+      }
+    ],
+    "type": "search_phase_execution_exception",
+    "reason": "all shards failed",
+    "phase": "query",
+    "grouped": true,
+    "failed_shards": [
+      {
+        "shard": 0,
+        "index": "blog_posts",
+        "node": "hupWdkj_RtmThGjNUiIt_w",
+        "reason": {
+          "type": "script_exception",
+          "reason": "runtime error",
+          "script_stack": [
+            "java.base/jdk.internal.util.Preconditions.outOfBounds(Preconditions.java:100)",
+            "java.base/jdk.internal.util.Preconditions.outOfBoundsCheckIndex(Preconditions.java:106)",
+            "java.base/jdk.internal.util.Preconditions.checkIndex(Preconditions.java:302)",
+            "java.base/java.util.Objects.checkIndex(Objects.java:365)",
+            "java.base/java.util.ArrayList.get(ArrayList.java:428)",
+            """return keywords[2].toUpperCase();
+          """,
+            "               ^---- HERE"
+          ],
+          "script": " ...",
+          "lang": "painless",
+          "position": {
+            "offset": 76,
+            "start": 61,
+            "end": 105
+          },
+          "caused_by": {
+            "type": "index_out_of_bounds_exception",
+            "reason": "index_out_of_bounds_exception: Index 2 out of bounds for length 2"
+          }
+        }
+      }
+    ],
+    "caused_by": {
+      "type": "index_out_of_bounds_exception",
+      "reason": "index_out_of_bounds_exception: Index 2 out of bounds for length 2"
+    }
+  },
+  "status": 400
+}
+```
+
+## Problematic code
+
+```json
+{
+  "aggs": {
+    "third_tag_stats": {
+      "terms": {
+        "script": {
+          "source": """
+            def keywords = params._source.tags;
+
+            return keywords[2].toUpperCase();
+          """,
+          "lang": "painless"
+        }
+      }
+    }
+  }
+}
+```
+
+## Root cause
+
+The error occurs because the script tries to access index 2 (the third element) in an array that only has two elements (indices 0, 1). Arrays in Painless are zero-indexed, so accessing an index greater than or equal to the array size causes an exception.
+
+## Solution: Check array bounds before accessing
+
+Always verify the size of an array before accessing specific indices:
+
+```json
+GET blog_posts/_search
+{
+  "size": 0,
+  "aggs": {
+    "third_tag_stats": {
+      "terms": {
+        "script": {
+          "source": """
+            def keywords = params._source.tags;
+
+            if (keywords.size() > 2) {
+              return keywords[2].toUpperCase();
+            } else {
+              return "NO_THIRD_TAG";
+            }
+          """,
+          "lang": "painless"
+        }
+      }
+    }
+  }
+}
+```
+
+## Sample document
+
+```json
+POST blog_posts/_doc
+{
+  "title": "Getting Started with Elasticsearch",
+  "content": "Learn the basics...",
+  "tags": ["elasticsearch", "tutorial"]
+}
+```
+
+## Results
+
+```json
+{
+  ...,
+  "hits": {
+    ...
+  },
+  "aggregations": {
+    "third_tag_stats": {
+      "doc_count_error_upper_bound": 0,
+      "sum_other_doc_count": 0,
+      "buckets": [
+        {
+          "key": "NO_THIRD_TAG",
+          "doc_count": 1
+        }
+      ]
+    }
+  }
+}
+```
+
+## Notes
+
+* **Array bounds:** Always check the size of an array before accessing specific indices.  
+* **Zero-indexed:** Remember that arrays start at index 0, so `size() - 1` is the last valid index.  
+* **Empty arrays:** Handle cases where arrays might be completely empty (`size() == 0`).

troubleshoot/elasticsearch/painless-date-math-errors.md

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+---
+navigation_title: Date math errors
+applies_to:
+  stack: ga
+  serverless: ga
+products:
+  - id: elasticsearch
+---
+
+# Troubleshoot date math errors in Painless
+
+Follow these guidelines to avoid [date](elasticsearch://reference/scripting-languages/painless/using-datetime-in-painless.md) operation errors in your Painless scripts.
+
+When you work with date fields in runtime mappings, accessing methods directly on the document field object can cause errors if the proper value accessor is not used.
+
+## Error
+
+```json
+{
+  "error": {
+    "root_cause": [
+      {
+        "type": "script_exception",
+        "reason": "runtime error",
+        "script_stack": [
+          """emit(orderDate.toInstant().toEpochMilli() + 14400000);
+        """,
+          "              ^---- HERE"
+        ],
+        "script": " ...",
+        "lang": "painless",
+        "position": {
+          "offset": 75,
+          "start": 61,
+          "end": 124
+        }
+      }
+    ],
+    "type": "search_phase_execution_exception",
+    "reason": "all shards failed",
+    "phase": "query",
+    "grouped": true,
+    "failed_shards": [
+      {
+        "shard": 0,
+        "index": "kibana_sample_data_ecommerce",
+        "node": "CxMTEjvKSEC0k0aTr4OM3A",
+        "reason": {
+          "type": "script_exception",
+          "reason": "runtime error",
+          "script_stack": [
+            """emit(orderDate.toInstant().toEpochMilli() + 14400000);
+        """,
+            "              ^---- HERE"
+          ],
+          "script": " ...",
+          "lang": "painless",
+          "position": {
+            "offset": 75,
+            "start": 61,
+            "end": 124
+          },
+          "caused_by": {
+            "type": "illegal_argument_exception",
+            "reason": "dynamic method [org.elasticsearch.index.fielddata.ScriptDocValues.Dates, toInstant/0] not found"
+          }
+        }
+      }
+    ]
+  },
+  "status": 400
+}
+```
+
+## Problematic code
+
+```json
+"script": {
+  "lang": "painless",
+  "source": """
+    def orderDate = doc['order_date'];
+    emit(orderDate.toInstant().toEpochMilli() + 14400000);
+  """
+}
+```
+
+## Root cause
+
+The script attempts to call `toInstant()` directly on a `ScriptDocValues.Dates` object. Date fields in Painless require accessing the `.value` property to get the actual date value before calling date methods.
+
+## Solution
+
+Access the date value using `.value` before calling date methods:
+
+```json
+"script": {
+  "lang": "painless",
+  "source": """
+    def orderDate = doc['order_date'].value; // Appended `.value` to the method.
+    emit(orderDate.toInstant().toEpochMilli() + 14400000);
+  """
+}
+```
+
+## Notes
+
+* Always use `.value` when accessing single values from document fields in Painless.  
+* Check for empty fields when the field might not exist in all documents.  
+* Date arithmetic should be performed on the actual date value, not the field container object.