Added comments , removed values only used for testing

src/backend/distributed/operations/auto_shard_split.c

@@ -37,14 +37,18 @@ typedef struct ShardInfoData
 	char *distributionColumn;
 	char *datatype;
 	char *shardname;
-    Oid tableId;
+	Oid tableId;
-    Oid distributionColumnId;
+	Oid distributionColumnId;
-
 }ShardInfoData;
 typedef ShardInfoData *ShardInfo;
 
-void ErrorOnConcurrentOperation(){
 
+/*
+ * It throws an error if a concurrent automatic shard split or Rebalance operation is happening.
+ */
+void
+ErrorOnConcurrentOperation()
+{
 	int64 jobId = 0;
 	if (HasNonTerminalJobOfType("rebalance", &jobId))
 	{
@@ -57,39 +61,49 @@ void ErrorOnConcurrentOperation(){
 	if (HasNonTerminalJobOfType("Automatic Shard Split", &jobId))
 	{
 		ereport(ERROR, (
-					errmsg("An automatic shard split is already running as job %ld", jobId),
+					errmsg("An automatic shard split is already running as job %ld",
-					errdetail("An automatic shard split was already scheduled as background job")));
+						   jobId),
+					errdetail(
+						"An automatic shard split was already scheduled as background job")));
 	}
 }
 
+
+/*
+ * For a given SplitPoints , it creates the SQL query for the shard Splitting
+ */
 StringInfo
-GetShardSplitQuery(ShardInfo shardinfo, List* SplitPoints)
+GetShardSplitQuery(ShardInfo shardinfo, List *SplitPoints)
 {
 	StringInfo splitQuery = makeStringInfo();
 
-    int64 length = list_length(SplitPoints);
+	int64 length = list_length(SplitPoints);
-    appendStringInfo(splitQuery,"SELECT citus_split_shard_by_split_points(%ld, ARRAY[",shardinfo->shardid);
+	appendStringInfo(splitQuery, "SELECT citus_split_shard_by_split_points(%ld, ARRAY[",
+					 shardinfo->shardid);
 
-    for (int i =0; i < length-1; i++)
+	for (int i = 0; i < length - 1; i++)
-    {
+	{
-      appendStringInfo(splitQuery,"'%ld',",DatumGetInt64(list_nth(SplitPoints,i)));  
+		appendStringInfo(splitQuery, "'%ld',", DatumGetInt64(list_nth(SplitPoints, i)));
+	}
+	appendStringInfo(splitQuery, "'%ld'], ARRAY[", DatumGetInt64(list_nth(SplitPoints,
+																		  length - 1)));
+
+	for (int i = 0; i < length; i++)
+	{
+		appendStringInfo(splitQuery, "%ld,", shardinfo->nodeid);
+	}
+	appendStringInfo(splitQuery, "%ld], 'block_writes')", shardinfo->nodeid);
 
-    }
-    appendStringInfo(splitQuery,"'%ld'], ARRAY[",DatumGetInt64(list_nth(SplitPoints,length-1)));
-    
-    for (int i =0; i < length; i++)
-    {
-        appendStringInfo(splitQuery,"%ld,",shardinfo->nodeid);
-    }
-    appendStringInfo(splitQuery,"%ld], 'block_writes')",shardinfo->nodeid);
-	
 	return splitQuery;
 }
 
-void
-ExecuteSplitBackgroundJob(int64 jobid, ShardInfo shardinfo, List* SplitPoints)
-{
 
+/*
+ * It creates a background job for citus_split_shard_by_split_points and executes it in background.
+ */
+void
+ExecuteSplitBackgroundJob(int64 jobid, ShardInfo shardinfo, List *SplitPoints)
+{
 	StringInfo splitQuery = makeStringInfo();
 	splitQuery = GetShardSplitQuery(shardinfo, SplitPoints);
 	ereport(LOG, (errmsg(splitQuery->data)));
@@ -100,10 +114,12 @@ ExecuteSplitBackgroundJob(int64 jobid, ShardInfo shardinfo, List* SplitPoints)
 	BackgroundTask *task = ScheduleBackgroundTask(jobid, superUserId, splitQuery->data, 0,
 												  NULL, 1, nodesInvolved);
 }
+
+
 /*
-* It executes a query to find the average hash value in a shard considering rows with a limit of 10GB .
+ * It executes a query to find the average hash value in a shard considering rows with a limit of 10GB .
-* 
+ * If there exists a hash value it is returned otherwise shardminvalue-1 is returned.
-*/
+ */
 int64
 ExecuteAvgHashQuery(ShardInfo shardinfo)
 {
@@ -111,7 +127,8 @@ ExecuteAvgHashQuery(ShardInfo shardinfo)
 	appendStringInfo(AvgHashQuery, "SELECT avg(h)::int,count(*)"
 								   " FROM (SELECT worker_hash(%s) h FROM %s TABLESAMPLE SYSTEM(least(10, 100*10000000000/citus_total_relation_size(%s)))"
 								   " WHERE worker_hash(%s)>=%ld AND worker_hash(%s)<=%ld) s",
-					 shardinfo->distributionColumn, shardinfo->tablename,quote_literal_cstr(shardinfo->tablename),
+					 shardinfo->distributionColumn, shardinfo->tablename,
+					 quote_literal_cstr(shardinfo->tablename),
 					 shardinfo->distributionColumn, shardinfo->shardminvalue,
 					 shardinfo->distributionColumn, shardinfo->shardmaxvalue
 					 );
@@ -139,10 +156,12 @@ ExecuteAvgHashQuery(ShardInfo shardinfo)
 		return shardinfo->shardminvalue - 1;
 	}
 }
+
+
 /*
  * This function executes a query and then decides whether a shard is subjected for isolation or average hash 2 way split.
  * If a tenant is found splitpoints for isolation is returned otherwise average hash value is returned.
-*/
+ */
 List *
 FindShardSplitPoints(ShardInfo shardinfo)
 {
@@ -152,50 +171,54 @@ FindShardSplitPoints(ShardInfo shardinfo)
 					 " FROM pg_stats s , unnest(most_common_vals::text::%s[],most_common_freqs) as res(val,freq)"
 					 " WHERE tablename = %s AND attname = %s AND freq > 0.2 $$)"
 					 " WHERE result <> '' AND shardid = %ld;",
-					 shardinfo->datatype, quote_literal_cstr(shardinfo->tablename), shardinfo->datatype,
+					 shardinfo->datatype, quote_literal_cstr(shardinfo->tablename),
+					 shardinfo->datatype,
 					 quote_literal_cstr(shardinfo->shardname),
-					 quote_literal_cstr(shardinfo->distributionColumn), shardinfo->shardid);
+					 quote_literal_cstr(shardinfo->distributionColumn),
+					 shardinfo->shardid);
 
 	ereport(LOG, errmsg("%s", CommonValueQuery->data));
-    List *SplitPoints = NULL;
+	List *SplitPoints = NULL;
-    MemoryContext originalContext = CurrentMemoryContext;
+	MemoryContext originalContext = CurrentMemoryContext;
 	SPI_connect();
 	SPI_exec(CommonValueQuery->data, 0);
-    MemoryContext spiContext = CurrentMemoryContext;
+	MemoryContext spiContext = CurrentMemoryContext;
 	int64 rowCount = SPI_processed;
-    int64 average,hashedValue;
+	int64 average, hashedValue;
 	ereport(LOG, errmsg("%ld", rowCount));
 
 	if (rowCount > 0)
 	{
 		SPITupleTable *tupletable = SPI_tuptable;
-        CitusTableCacheEntry *cacheEntry = GetCitusTableCacheEntry(shardinfo->tableId);
+		CitusTableCacheEntry *cacheEntry = GetCitusTableCacheEntry(shardinfo->tableId);
 		for (int rowIndex = 0; rowIndex < rowCount; rowIndex++)
 		{
 			HeapTuple tuple = tupletable->vals[rowIndex];
 			char *commonValue = SPI_getvalue(tuple, tupletable->tupdesc, 2);
 			ereport(LOG, errmsg("%s", commonValue));
-            Datum tenantIdDatum = StringToDatum(commonValue, shardinfo->distributionColumnId);
+			Datum tenantIdDatum = StringToDatum(commonValue,
-            Datum hashedValueDatum = FunctionCall1Coll(cacheEntry->hashFunction,
+												shardinfo->distributionColumnId);
-											   cacheEntry->partitionColumn->varcollid,
+			Datum hashedValueDatum = FunctionCall1Coll(cacheEntry->hashFunction,
-											   tenantIdDatum);
+													   cacheEntry->partitionColumn->
-	        hashedValue = DatumGetInt32(hashedValueDatum);
+													   varcollid,
-            ereport(LOG,errmsg("%ld",hashedValue));
+													   tenantIdDatum);
-            MemoryContextSwitchTo(originalContext);
+			hashedValue = DatumGetInt32(hashedValueDatum);
-             if (hashedValue == shardinfo->shardminvalue)
+			ereport(LOG, errmsg("%ld", hashedValue));
-            {
+			MemoryContextSwitchTo(originalContext);
-                SplitPoints = lappend(SplitPoints,Int64GetDatum(hashedValue));
+			if (hashedValue == shardinfo->shardminvalue)
-            }
+			{
-            else if (hashedValue == shardinfo->shardmaxvalue)
+				SplitPoints = lappend(SplitPoints, Int64GetDatum(hashedValue));
-            {
+			}
-                SplitPoints = lappend(SplitPoints,Int64GetDatum(hashedValue-1));
+			else if (hashedValue == shardinfo->shardmaxvalue)
-            }
+			{
-            else
+				SplitPoints = lappend(SplitPoints, Int64GetDatum(hashedValue - 1));
-            {   
+			}
-                SplitPoints = lappend(SplitPoints,Int64GetDatum(hashedValue-1));
+			else
-                SplitPoints = lappend(SplitPoints,Int64GetDatum(hashedValue));;
+			{
-            }
+				SplitPoints = lappend(SplitPoints, Int64GetDatum(hashedValue - 1));
-            MemoryContextSwitchTo(spiContext);	
+				SplitPoints = lappend(SplitPoints, Int64GetDatum(hashedValue));
+			}
+			MemoryContextSwitchTo(spiContext);
 		}
 		SPI_freetuptable(tupletable);
 	}
@@ -203,41 +226,52 @@ FindShardSplitPoints(ShardInfo shardinfo)
 	{
 		average = ExecuteAvgHashQuery(shardinfo);
 		ereport(LOG, errmsg("%ld", average));
-		
 	}
 
 	SPI_finish();
 
-    if(rowCount>0){
+	if (rowCount > 0)
-        list_sort(SplitPoints, list_int_cmp);
+	{
-    }else{
+		list_sort(SplitPoints, list_int_cmp);
-        if(shardinfo->shardminvalue<=average){
+	}
-        SplitPoints = lappend(SplitPoints,Int64GetDatum(average));
+	else
-        }
+	{
-    }
+		if (shardinfo->shardminvalue <= average)
-   
+		{
-    return SplitPoints;
+			SplitPoints = lappend(SplitPoints, Int64GetDatum(average));
-    
+		}
+	}
 
+	return SplitPoints;
 }
+
+
 /*
  * This function calculates the split points of the shard to split and then executes the background job.
-*/
+ */
 void
-ScheduleShardSplit(ShardInfo shardinfo){
+ScheduleShardSplit(ShardInfo shardinfo)
-
+{
-    List* SplitPoints = FindShardSplitPoints(shardinfo);
+	List *SplitPoints = FindShardSplitPoints(shardinfo);
-    if(list_length(SplitPoints)>0){
+	if (list_length(SplitPoints) > 0)
-    // int64 jobId = CreateBackgroundJob("Automatic Shard Split", "Split using SplitPoints List");
+	{
-    ereport(LOG,errmsg("%s",GetShardSplitQuery(shardinfo,SplitPoints)->data));
+		int64 jobId = CreateBackgroundJob("Automatic Shard Split",
-    }else{
+										  "Split using SplitPoints List");
-        ereport(LOG,errmsg("No Splitpoints for shard split"));
+		ExecuteSplitBackgroundJob(jobId, shardinfo, SplitPoints);
-    }
+	}
-
+	else
-
+	{
+		ereport(LOG, errmsg("No Splitpoints for shard split"));
+	}
 }
 
 
+/*
+ * citus_auto_shard_split_start finds shards whose colocation group has total size greater than threshold
+ * and from that extracts the shard with the maximum size . It isolates the shards if the shard has common
+ * tenant values otherwise it 2 way splits it on the basis of average hash value.
+ *
+ */
 Datum
 citus_auto_shard_split_start(PG_FUNCTION_ARGS)
 {
@@ -256,7 +290,7 @@ citus_auto_shard_split_start(PG_FUNCTION_ARGS)
 		" FROM citus_shards cs JOIN pg_dist_shard ps USING(shardid)"
 		" WINDOW w AS (PARTITION BY colocation_id, shardminvalue ORDER BY shard_size DESC) )as t where total_sum >= %ld )"
 		" AS max_sizes ON cs.shardid=max_sizes.shardid AND cs.shard_size = max_sizes.max_size JOIN citus_tables ct ON cs.table_name = ct.table_name AND pd.shardminvalue <> pd.shardmaxvalue AND pd.shardminvalue <> ''",
-		0
+		MaxShardSize
 		);
 
 	ereport(LOG, errmsg("%s", query->data));
@@ -298,21 +332,24 @@ citus_auto_shard_split_start(PG_FUNCTION_ARGS)
 		shardinfo.tablename = SPI_getvalue(tuple, tupletable->tupdesc, 7);
 
 		StringInfo shardnameQuery = makeStringInfo();
-		appendStringInfo(shardnameQuery,"%s_%ld",SPI_getvalue(tuple,tupletable->tupdesc,9),shardinfo.shardid);
+		appendStringInfo(shardnameQuery, "%s_%ld", SPI_getvalue(tuple,
+																tupletable->tupdesc, 9),
+						 shardinfo.shardid);
 		shardinfo.shardname = shardnameQuery->data;
 
 		Datum tableIdDatum = SPI_getbinval(tuple, tupletable->tupdesc, 7, &isnull);
 		shardinfo.tableId = DatumGetObjectId(tableIdDatum);
-		shardinfo.distributionColumnId = ColumnTypeIdForRelationColumnName(shardinfo.tableId,
+		shardinfo.distributionColumnId = ColumnTypeIdForRelationColumnName(
-																	 shardinfo.
+			shardinfo.tableId,
-																	 distributionColumn);
+			shardinfo.
+			distributionColumn);
 		shardinfo.datatype = format_type_be(shardinfo.distributionColumnId);
 
-		char * shardSplitMode;
+		char *shardSplitMode;
-		// Oid shardTransferModeOid = PG_GETARG_OID(0);
+		/* Oid shardTransferModeOid = PG_GETARG_OID(0); */
-		// Datum enumLabelDatum = DirectFunctionCall1(enum_out, shardTransferModeOid);
+		/* Datum enumLabelDatum = DirectFunctionCall1(enum_out, shardTransferModeOid); */
-		// char *enumLabel = DatumGetCString(enumLabelDatum);
+		/* char *enumLabel = DatumGetCString(enumLabelDatum); */
-		// ereport(LOG,errmsg("%s",enumLabel));
+		/* ereport(LOG,errmsg("%s",enumLabel)); */
 
 		ScheduleShardSplit(&shardinfo);
 		ereport(LOG, (errmsg(

src/backend/distributed/sql/udfs/citus_auto_shard_split_start/12.0-1.sql

@@ -10,4 +10,4 @@ COMMENT ON FUNCTION pg_catalog.citus_auto_shard_split_start()
 
     IS 'automatically split the necessary shards in the cluster in the background';
 
-GRANT EXECUTE ON FUNCTION pg_catalog.citus_auto_shard_split_start() TO PUBLIC;
+GRANT EXECUTE ON FUNCTION pg_catalog.citus_auto_shard_split_start() TO PUBLIC;

src/backend/distributed/sql/udfs/citus_auto_shard_split_start/latest.sql

@@ -1,5 +1,5 @@
 CREATE OR REPLACE FUNCTION pg_catalog.citus_auto_shard_split_start(
-  
+
     )
     RETURNS VOID
 
@@ -11,4 +11,4 @@ COMMENT ON FUNCTION pg_catalog.citus_auto_shard_split_start()
 
     IS 'automatically split the necessary shards in the cluster in the background';
 
-GRANT EXECUTE ON FUNCTION pg_catalog.citus_auto_shard_split_start() TO PUBLIC;
+GRANT EXECUTE ON FUNCTION pg_catalog.citus_auto_shard_split_start() TO PUBLIC;