Update comment about ExprState.escontext

The updated comment provides more helpful guidance by mentioning that
escontext should be set when soft error handling is needed.

Reported-by: Jian He 
Discussion: https://postgr.es/m/CACJufxEo4sUjKCYtda0_qt9tazqqKPmF1cqhW9KBOUeJFqQd2g@mail.gmail.com
Backpatch-through: 17

diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index b62c96f2064895831dca89ab945777fcda9b2017..cd1b16296b5a2fee1d5b4e38e52479c2d04f279c 100644 (file)
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -132,8 +132,10 @@ typedef struct ExprState
    bool       *innermost_domainnull;
 
    /*
-    * For expression nodes that support soft errors.  Should be set to NULL
-    * before calling ExecInitExprRec() if the caller wants errors thrown.
+    * For expression nodes that support soft errors. Should be set to NULL if
+    * the caller wants errors to be thrown. Callers that do not want errors
+    * thrown should set it to a valid ErrorSaveContext before calling
+    * ExecInitExprRec().
     */
    ErrorSaveContext *escontext;
 } ExprState;