all: get rid of query pushdown to simplify query path

CHANGELOG.md

@@ -51,6 +51,8 @@ We use *breaking :warning:* to mark changes that are not backward compatible (re
 
 ### Removed
 
+- [#7014](https://github.com/thanos-io/thanos/pull/7014) *: *breaking :warning:* Removed experimental query pushdown feature to simplify query path. This feature has had high complexity for too little benefits. The responsibility for query pushdown will be moved to the distributed mode of the new 'thanos' promql engine.
+
 ## [v0.33.0](https://github.com/thanos-io/thanos/tree/release-0.33) - 18.12.2023
 
 ### Fixed

cmd/thanos/query.go

@@ -197,7 +197,7 @@ func registerQuery(app *extkingpin.App) {
 
 	activeQueryDir := cmd.Flag("query.active-query-path", "Directory to log currently active queries in the queries.active file.").Default("").String()
 
-	featureList := cmd.Flag("enable-feature", "Comma separated experimental feature names to enable.The current list of features is "+queryPushdown+".").Default("").Strings()
+	featureList := cmd.Flag("enable-feature", "Comma separated experimental feature names to enable.The current list of features is empty.").Hidden().Default("").Strings()
 
 	enableExemplarPartialResponse := cmd.Flag("exemplar.partial-response", "Enable partial response for exemplar endpoint. --no-exemplar.partial-response for disabling.").
 		Hidden().Default("true").Bool()
@@ -232,17 +232,16 @@ func registerQuery(app *extkingpin.App) {
 			return errors.Wrap(err, "parse federation labels")
 		}
 
-		var enableQueryPushdown bool
 		for _, feature := range *featureList {
-			if feature == queryPushdown {
-				enableQueryPushdown = true
-			}
 			if feature == promqlAtModifier {
 				level.Warn(logger).Log("msg", "This option for --enable-feature is now permanently enabled and therefore a no-op.", "option", promqlAtModifier)
 			}
 			if feature == promqlNegativeOffset {
 				level.Warn(logger).Log("msg", "This option for --enable-feature is now permanently enabled and therefore a no-op.", "option", promqlNegativeOffset)
 			}
+			if feature == queryPushdown {
+				level.Warn(logger).Log("msg", "This option for --enable-feature is now permanently deprecated and therefore ignored.", "option", queryPushdown)
+			}
 		}
 
 		httpLogOpts, err := logging.ParseHTTPOptions(reqLogConfig)
@@ -335,7 +334,6 @@ func registerQuery(app *extkingpin.App) {
 			*strictEndpoints,
 			*strictEndpointGroups,
 			*webDisableCORS,
-			enableQueryPushdown,
 			*alertQueryURL,
 			*grpcProxyStrategy,
 			component.Query,
@@ -417,7 +415,6 @@ func runQuery(
 	strictEndpoints []string,
 	strictEndpointGroups []string,
 	disableCORS bool,
-	enableQueryPushdown bool,
 	alertQueryURL string,
 	grpcProxyStrategy string,
 	comp component.Component,
@@ -708,7 +705,6 @@ func runQuery(
 			enableTargetPartialResponse,
 			enableMetricMetadataPartialResponse,
 			enableExemplarPartialResponse,
-			enableQueryPushdown,
 			queryReplicaLabels,
 			flagsMap,
 			defaultRangeQueryStep,

docs/components/query.md

@@ -286,9 +286,6 @@ Flags:
       --alert.query-url=ALERT.QUERY-URL
                                  The external Thanos Query URL that would be set
                                  in all alerts 'Source' field.
-      --enable-feature= ...      Comma separated experimental feature names
-                                 to enable.The current list of features is
-                                 query-pushdown.
       --endpoint=<endpoint> ...  Addresses of statically configured Thanos
                                  API servers (repeatable). The scheme may be
                                  prefixed with 'dns+' or 'dnssrv+' to detect

pkg/api/query/grpc.go

@@ -97,7 +97,6 @@ func (g *GRPCAPI) Query(request *querypb.QueryRequest, server querypb.Query_Quer
 		storeMatchers,
 		maxResolution,
 		request.EnablePartialResponse,
-		request.EnableQueryPushdown,
 		false,
 		request.ShardInfo,
 		query.NoopSeriesStatsReporter,
@@ -195,7 +194,6 @@ func (g *GRPCAPI) QueryRange(request *querypb.QueryRangeRequest, srv querypb.Que
 		storeMatchers,
 		maxResolution,
 		request.EnablePartialResponse,
-		request.EnableQueryPushdown,
 		false,
 		request.ShardInfo,
 		query.NoopSeriesStatsReporter,

pkg/api/query/querypb/query.proto

@@ -41,13 +41,14 @@ message QueryRequest {
 
   bool enableDedup = 7;
   bool enablePartialResponse = 8;
-  bool enableQueryPushdown = 9;
   bool skipChunks = 10;
 
   ShardInfo shard_info = 11;
 
   int64 lookback_delta_seconds = 12;
   EngineType engine = 13;
+
+  reserved 9;
 }
 
 message StoreMatchers {
@@ -80,12 +81,13 @@ message QueryRangeRequest {
 
   bool enableDedup = 9;
   bool enablePartialResponse = 10;
-  bool enableQueryPushdown = 11;
   bool skipChunks = 12;
 
   ShardInfo shard_info = 13;
   int64 lookback_delta_seconds = 14;
   EngineType engine = 15;
+
+  reserved 11;
 }
 
 message QueryRangeResponse {