Prepare schema tracking for all UDFs (#15732)

changelog/20.0/20.0.0/summary.md

@@ -25,6 +25,7 @@
   - **[Flag changes](#flag-changes)**
     - [`pprof-http` default change](#pprof-http-default)
     - [New `healthcheck-dial-concurrency` flag](#healthcheck-dial-concurrency-flag)
+    - [New `track-udfs` vtgate flag](#vtgate-track-udfs-flag)
 - **[Minor Changes](#minor-changes)**
   - **[New Stats](#new-stats)**
     - [VTTablet Query Cache Hits and Misses](#vttablet-query-cache-hits-and-misses)
@@ -189,7 +190,9 @@ More details about how it works is available in [MySQL Docs](https://dev.mysql.c
 VTGate can track any user defined functions for better planning.
 User Defined Functions (UDFs) should be directly loaded in the underlying MySQL.
 
-It should be enabled in VTGate with the `--enable-udfs` flag.
+It should be enabled in VTGate with the `--track-udfs` flag.
+This will enable the tracking of UDFs in VTGate and will be used for planning.
+Without this flag, VTGate will not be aware that there might be aggregating user-defined functions in the query that need to be pushed down to MySQL.
 
 More details about how to load UDFs is available in [MySQL Docs](https://dev.mysql.com/doc/extending-mysql/8.0/en/adding-loadable-function.html)
 
@@ -205,6 +208,10 @@ To continue enabling these endpoints, explicitly set `--pprof-http` when startin
 
 The new `--healthcheck-dial-concurrency` flag defines the maximum number of healthcheck connections that can open concurrently. This limit is to avoid hitting Go runtime panics on deployments watching enough tablets [to hit the runtime's maximum thread limit of `10000`](https://pkg.go.dev/runtime/debug#SetMaxThreads) due to blocking network syscalls. This flag applies to `vtcombo`, `vtctld` and `vtgate` only and a value less than the runtime max thread limit _(`10000`)_ is recommended.
 
+#### <a id="vtgate-track-udfs-flag"/>New `--track-udfs` vtgate flag
+
+The new `--track-udfs` flag enables VTGate to track user defined functions for better planning.
+
 ## <a id="minor-changes"/>Minor Changes
 
 ### <a id="new-stats"/>New Stats

go/flags/endtoend/flags_test.go

@@ -118,7 +118,7 @@ var (
 func TestHelpOutput(t *testing.T) {
 	wd, err := os.Getwd()
 	require.NoError(t, err)
-
+	t.Parallel()
 	args := []string{"--help"}
 	for binary, helptext := range helpOutput {
 		t.Run(binary, func(t *testing.T) {

go/flags/endtoend/vtcombo.txt

@@ -115,7 +115,6 @@ Flags:
       --enable-partial-keyspace-migration                                (Experimental) Follow shard routing rules: enable only while migrating a keyspace shard by shard. See documentation on Partial MoveTables for more. (default false)
       --enable-per-workload-table-metrics                                If true, query counts and query error metrics include a label that identifies the workload
       --enable-tx-throttler                                              Synonym to -enable_tx_throttler
-      --enable-udfs                                                      Enable UDFs support in vtgate.
       --enable-views                                                     Enable views support in vtgate.
       --enable_buffer                                                    Enable buffering (stalling) of primary traffic during failovers.
       --enable_buffer_dry_run                                            Detect and log failover events, but do not actually buffer requests.
@@ -377,6 +376,7 @@ Flags:
       --tracing-enable-logging                                           whether to enable logging in the tracing service
       --tracing-sampling-rate float                                      sampling rate for the probabilistic jaeger sampler (default 0.1)
       --tracing-sampling-type string                                     sampling strategy to use for jaeger. possible values are 'const', 'probabilistic', 'rateLimiting', or 'remote' (default "const")
+      --track-udfs                                                       Track UDFs in vtgate.
       --track_schema_versions                                            When enabled, vttablet will store versions of schemas at each position that a DDL is applied and allow retrieval of the schema corresponding to a position
       --transaction-log-stream-handler string                            URL handler for streaming transactions log (default "/debug/txlog")
       --transaction_limit_by_component                                   Include CallerID.component when considering who the user is for the purpose of transaction limit.

go/flags/endtoend/vtgate.txt

@@ -54,7 +54,6 @@ Flags:
       --discovery_low_replication_lag duration                           Threshold below which replication lag is considered low enough to be healthy. (default 30s)
       --emit_stats                                                       If set, emit stats to push-based monitoring and stats backends
       --enable-partial-keyspace-migration                                (Experimental) Follow shard routing rules: enable only while migrating a keyspace shard by shard. See documentation on Partial MoveTables for more. (default false)
-      --enable-udfs                                                      Enable UDFs support in vtgate.
       --enable-views                                                     Enable views support in vtgate.
       --enable_buffer                                                    Enable buffering (stalling) of primary traffic during failovers.
       --enable_buffer_dry_run                                            Detect and log failover events, but do not actually buffer requests.
@@ -229,6 +228,7 @@ Flags:
       --tracing-enable-logging                                           whether to enable logging in the tracing service
       --tracing-sampling-rate float                                      sampling rate for the probabilistic jaeger sampler (default 0.1)
       --tracing-sampling-type string                                     sampling strategy to use for jaeger. possible values are 'const', 'probabilistic', 'rateLimiting', or 'remote' (default "const")
+      --track-udfs                                                       Track UDFs in vtgate.
       --transaction_mode string                                          SINGLE: disallow multi-db transactions, MULTI: allow multi-db transactions with best effort commit, TWOPC: allow multi-db transactions with 2pc commit (default "MULTI")
       --truncate-error-len int                                           truncate errors sent to client if they are longer than this value (0 means do not truncate)
       --v Level                                                          log level for V logs