Remove 0=0 /* _index = table_name /* from generated SQL (#1303)

Noticed it at the customer
#1199

Before, for my test request we generated `WHERE 0=0 /* _index=\'Quesma\'
*/`
Now we generate `WHERE true`, which is IMO a style improvement.
(I've grepped a lot and I'm pretty sure it's the only place in code
where we generate this `0=0` thing)

Ideally I'd write a simple transformation to remove unnecessary `true`
from the `WHERE`, but that's more work and I propose to do it in another
PR, not very urgently.
(Actually I'll make Claude 3.7 do it, it should manage, shouldn't it?)

Author: trzysiek

quesma/parsers/elastic_query_dsl/query_parser.go

@@ -490,9 +490,8 @@ func (cw *ClickhouseQueryTranslator) parseTerm(queryMap QueryMap) model.SimpleQu
 	if len(queryMap) == 1 {
 		for k, v := range queryMap {
 			if k == "_index" { // index is a table name, already taken from URI and moved to FROM clause
-				logger.Warn().Msgf("term %s=%v in query body, ignoring in result SQL", k, v)
-				whereClause = model.NewInfixExpr(model.NewLiteral("0"), "=", model.NewLiteral("0 /* "+k+"="+sprint(v)+" */"))
-				return model.NewSimpleQuery(whereClause, true)
+				logger.WarnWithCtx(cw.Ctx).Msgf("term %s=%v in query body, ignoring in result SQL", k, v)
+				return model.NewSimpleQuery(model.TrueExpr, true)
 			}
 			fieldName := ResolveField(cw.Ctx, k, cw.Schema)
 			whereClause = model.NewInfixExpr(model.NewColumnRef(fieldName), "=", model.NewLiteral(sprint(v)))

quesma/testdata/requests.go

@@ -2504,6 +2504,23 @@ Men\\'s Clothing \\\\ 	%' LIMIT 10`},
 		},
 		[]string{},
 	},
+	{ // [48]
+		"_index term",
+		`{
+			"query": { /*one comment */
+				"bool": {
+					"must": {
+						"term": { "_index": "Quesma" }
+					}
+				}
+			},
+			"track_total_hits": false
+		}`,
+		[]string{"true"},
+		model.ListAllFields,
+		[]string{`SELECT "message" FROM ` + TableName + " WHERE true"},
+		[]string{},
+	},
 }
 
 var TestSearchRuntimeMappings = []SearchTestCase{