pkg/ddl,planner: add TiKV space precheck for DXF add-index

Author: expxiaoli

docs/plans/2026-05-14-add-index-tikv-space-precheck.md

@@ -138,6 +138,7 @@ go_library(
         "//pkg/parser/opcode",
         "//pkg/parser/terror",
         "//pkg/parser/types",
+        "//pkg/planner/util/rowsize",
         "//pkg/privilege",
         "//pkg/resourcegroup",
         "//pkg/resourcemanager/pool/workerpool",

pkg/ddl/BUILD.bazel

@@ -48,10 +48,20 @@ type BackfillTaskMeta struct {
 	// For now, only index type is supported.
 	EleTypeKey []byte `json:"ele_type_key"`
 
-	CloudStorageURI       string                  `json:"cloud_storage_uri"`
-	EstimateRowSize       int                     `json:"estimate_row_size"`
-	MergeTempIndex        bool                    `json:"merge_temp_index"`
-	InitialTiKVStoreUsage *TiKVStoreUsageSnapshot `json:"initial_tikv_store_usage,omitempty"`
+	CloudStorageURI                  string                  `json:"cloud_storage_uri"`
+	EstimateRowSize                  int                     `json:"estimate_row_size"`
+	MergeTempIndex                   bool                    `json:"merge_temp_index"`
+	InitialTiKVStoreUsage            *TiKVStoreUsageSnapshot `json:"initial_tikv_store_usage,omitempty"`
+	InitialTiKVCapacity              *TiKVClusterCapacity    `json:"initial_tikv_capacity,omitempty"`
+	BasicPredictedTiKVIndexBytes     uint64                  `json:"basic_predicted_tikv_index_bytes,omitempty"`
+	RepresentPredictedTiKVIndexBytes uint64                  `json:"represent_predicted_tikv_index_bytes,omitempty"`
+	SamplePredictedTiKVIndexBytes    uint64                  `json:"sample_predicted_tikv_index_bytes,omitempty"`
+	SamplePredictionRegionCount      int                     `json:"sample_prediction_region_count,omitempty"`
+	SamplePredictionRowCount         int                     `json:"sample_prediction_row_count,omitempty"`
+	SamplePredictionReadErrorCount   int                     `json:"sample_prediction_read_error_count,omitempty"`
+	// PredictedTiKVIndexBytes is kept for compatibility with task metadata written by
+	// earlier builds. New task submissions store the sample-model prediction here.
+	PredictedTiKVIndexBytes uint64 `json:"predicted_tikv_index_bytes,omitempty"`
 
 	Version int `json:"version,omitempty"`
 }
@@ -62,6 +72,24 @@ type TiKVStoreUsageSnapshot struct {
 	StoreCount int    `json:"store_count"`
 }
 
+// TiKVStoreCapacity contains per-store capacity details needed by DXF add-index
+// capacity precheck and post-task observation.
+type TiKVStoreCapacity struct {
+	StoreID        int64  `json:"store_id"`
+	TotalBytes     uint64 `json:"total_bytes"`
+	AvailableBytes uint64 `json:"available_bytes"`
+	UsedBytes      uint64 `json:"used_bytes"`
+}
+
+// TiKVClusterCapacity is the aggregated TiKV capacity snapshot collected from PD.
+type TiKVClusterCapacity struct {
+	TotalBytes     uint64              `json:"total_bytes"`
+	AvailableBytes uint64              `json:"available_bytes"`
+	UsedBytes      uint64              `json:"used_bytes"`
+	StoreCount     int                 `json:"store_count"`
+	Stores         []TiKVStoreCapacity `json:"stores,omitempty"`
+}
+
 // BackfillSubTaskMeta is the sub-task meta for backfilling index.
 type BackfillSubTaskMeta struct {
 	external.BaseExternalMeta