[#18082] YSQL: Stop using ForeignScan for YB relations

Summary:
Since implementation of aggregate pushdown for scan types other than
ForeignScan, the ForeignScan and the YbSeqScan are functionally
equivalent, so we switch to using the YbSeqScan, as it is more unified
with IndexScan and IndexOnlyScan, which are also used to scan YB
relation. Unification should make future developments easier.

For consistency with previous design decision explain now shows "Seq Scan"
if the plan node is a YbSeqScan node, hiding implementation details from the
end user. Though YbSeqScan shows "Filter" and "Remote Filter" in different
order, if both are present, so there are changes in the expected EXPLAIN output.
The order of YbSeqScan filters consistent with  the order of index scan and
matches their evaluation order (remote filter goes first).

There is no known way to force ForeignScan-based scan on Yugabyte tables.
To help catch such cases, if any, the ForeignScan plan node on Yugabyte tables
now shows "YB Foreign Scan" in the EXPLAIN output.
Jira: DB-7124

Test Plan:
Make sure existing regressions tests work.
Modifications to expected output are needed due to differencies in
EXPLAIN output.

Reviewers: jason, telgersma

Reviewed By: jason, telgersma

Subscribers: ssong, yql

Differential Revision: https://phorge.dev.yugabyte.com/D27297

java/yb-pgsql/src/test/java/org/yb/pgsql/ExplainAnalyzeUtils.java

@@ -34,8 +34,8 @@ public class ExplainAnalyzeUtils {
   public static final String NODE_SEQ_SCAN = "Seq Scan";
   public static final String NODE_SORT = "Sort";
   public static final String NODE_VALUES_SCAN = "Values Scan";
+
   public static final String NODE_YB_BATCHED_NESTED_LOOP = "YB Batched Nested Loop";
-  public static final String NODE_YB_SEQ_SCAN = "YB Seq Scan";
 
   public static final String OPERATION_INSERT = "Insert";
   public static final String OPERATION_UPDATE = "Update";

java/yb-pgsql/src/test/java/org/yb/pgsql/TestPgAutoExplain.java

@@ -13,14 +13,6 @@
 package org.yb.pgsql;
 
 import static org.yb.pgsql.ExplainAnalyzeUtils.NODE_SEQ_SCAN;
-import static org.yb.pgsql.ExplainAnalyzeUtils.NODE_YB_SEQ_SCAN;
-import static org.yb.pgsql.ExplainAnalyzeUtils.NODE_INDEX_SCAN;
-import static org.yb.pgsql.ExplainAnalyzeUtils.NODE_INDEX_ONLY_SCAN;
-import static org.yb.pgsql.ExplainAnalyzeUtils.NODE_VALUES_SCAN;
-import static org.yb.pgsql.ExplainAnalyzeUtils.NODE_NESTED_LOOP;
-import static org.yb.pgsql.ExplainAnalyzeUtils.NODE_MODIFY_TABLE;
-import static org.yb.pgsql.ExplainAnalyzeUtils.NODE_FUNCTION_SCAN;
-import static org.yb.pgsql.ExplainAnalyzeUtils.NODE_RESULT;
 import static org.yb.AssertionWrappers.assertEquals;
 import static org.yb.AssertionWrappers.assertTrue;
 
@@ -31,7 +23,6 @@
 import java.util.List;
 import java.util.ArrayList;
 import java.util.Collections;
-import java.lang.Character;
 import java.io.StringWriter;
 import java.io.PrintWriter;
 
@@ -43,14 +34,12 @@
 import org.yb.util.json.Checker;
 import org.yb.util.json.Checkers;
 import org.yb.util.json.JsonUtil;
-import org.yb.util.json.ObjectChecker;
 import org.yb.pgsql.ExplainAnalyzeUtils.PlanCheckerBuilder;
 import org.yb.pgsql.ExplainAnalyzeUtils.TopLevelCheckerBuilder;
 import org.yb.minicluster.LogErrorListener;
 import org.yb.minicluster.MiniYBDaemon;
 import org.yb.util.BuildTypeUtil;
 
-import org.yb.util.json.ValueChecker;
 import org.yb.YBTestRunner;
 
 import com.google.gson.JsonElement;
@@ -166,7 +155,7 @@ public void testDistOn() throws Exception {
             TABLE_NAME, TABLE_NAME),
         makeTopLevelBuilder()
             .plan(makePlanBuilder()
-                .nodeType(NODE_YB_SEQ_SCAN)
+                .nodeType(NODE_SEQ_SCAN)
                 .relationName(TABLE_NAME)
                 .alias(TABLE_NAME)
                 .storageTableReadRequests(Checkers.greaterOrEqual(0))
@@ -187,7 +176,7 @@ public void testDistOff() throws Exception {
             TABLE_NAME, TABLE_NAME),
         makeTopLevelBuilder()
             .plan(makePlanBuilder()
-                .nodeType(NODE_YB_SEQ_SCAN)
+                .nodeType(NODE_SEQ_SCAN)
                 .relationName(TABLE_NAME)
                 .alias(TABLE_NAME)
                 .actualStartupTime(Checkers.greaterOrEqual(0.0))
@@ -211,7 +200,7 @@ public void testAnalyzeOff() throws Exception {
             TABLE_NAME, TABLE_NAME),
         makeTopLevelBuilder()
             .plan(makePlanBuilder()
-                .nodeType(NODE_YB_SEQ_SCAN)
+                .nodeType(NODE_SEQ_SCAN)
                 // Startup cost and total cost because auto_explain
                 .startupCost(Checkers.greaterOrEqual(0.0))
                 .totalCost(Checkers.greaterOrEqual(0.0))

java/yb-pgsql/src/test/java/org/yb/pgsql/TestPgCardinalityEstimation.java

@@ -19,7 +19,6 @@
 import static org.yb.pgsql.ExplainAnalyzeUtils.NODE_MERGE_JOIN;
 import static org.yb.pgsql.ExplainAnalyzeUtils.NODE_SEQ_SCAN;
 import static org.yb.pgsql.ExplainAnalyzeUtils.NODE_SORT;
-import static org.yb.pgsql.ExplainAnalyzeUtils.NODE_YB_SEQ_SCAN;
 import org.yb.pgsql.ExplainAnalyzeUtils.PlanCheckerBuilder;
 import org.yb.pgsql.ExplainAnalyzeUtils.TopLevelCheckerBuilder;
 
@@ -167,7 +166,7 @@ public void testMergeJoinWithIndex() throws Exception {
                               .planRows(Checkers.greater(1))
                               .plans(
                                   makePlanBuilder()
-                                      .nodeType(NODE_YB_SEQ_SCAN)
+                                      .nodeType(NODE_SEQ_SCAN)
                                       .relationName(TABLE_NAME)
                                       .alias("t2")
                                       .planRows(Checkers.equal(TABLE_ROWS))
@@ -185,7 +184,7 @@ public void testMergeJoinWithIndex() throws Exception {
                                                   .nodeType(NODE_SORT)
                                                   .planRows(Checkers.greater(1))
                                                   .plans(makePlanBuilder()
-                                                      .nodeType(NODE_YB_SEQ_SCAN)
+                                                      .nodeType(NODE_SEQ_SCAN)
                                                       .relationName(TABLE_NAME)
                                                       .alias("t1")
                                                       .planRows(Checkers.greater(1))
@@ -199,7 +198,7 @@ public void testMergeJoinWithIndex() throws Exception {
                                                   .nodeType(NODE_SORT)
                                                   .planRows(Checkers.equal(TABLE_ROWS))
                                                   .plans(makePlanBuilder()
-                                                      .nodeType(NODE_YB_SEQ_SCAN)
+                                                      .nodeType(NODE_SEQ_SCAN)
                                                       .relationName(TABLE_NAME)
                                                       .alias("t3")
                                                       .planRows(Checkers.equal(TABLE_ROWS))

java/yb-pgsql/src/test/java/org/yb/pgsql/TestPgColumnReadEfficiency.java

@@ -13,28 +13,16 @@
 
 package org.yb.pgsql;
 
-import static org.yb.AssertionWrappers.assertEquals;
-import static org.yb.AssertionWrappers.assertGreaterThan;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import com.google.common.collect.Streams;
-import com.google.gson.JsonObject;
-import com.google.gson.JsonParser;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.yb.util.YBTestRunnerNonTsanOnly;
 
-import java.sql.SQLException;
 import java.sql.Statement;
-import java.util.ArrayList;
-import java.util.Collections;
-import java.util.Comparator;
 import java.util.List;
 import java.util.Map;
-import java.util.stream.Collectors;
-import java.util.stream.IntStream;
-import java.util.stream.Stream;
 import java.util.Arrays;
 
 import com.google.common.collect.Range;
@@ -45,7 +33,6 @@
 import static org.yb.pgsql.ExplainAnalyzeUtils.NODE_INDEX_SCAN;
 import static org.yb.pgsql.ExplainAnalyzeUtils.NODE_INDEX_ONLY_SCAN;
 import static org.yb.pgsql.ExplainAnalyzeUtils.NODE_SEQ_SCAN;
-import static org.yb.pgsql.ExplainAnalyzeUtils.NODE_YB_SEQ_SCAN;
 
 @RunWith(YBTestRunnerNonTsanOnly.class)
 public class TestPgColumnReadEfficiency extends BasePgSQLTest {
@@ -127,7 +114,7 @@ public void testScanRowSize() throws Exception {
             ssEstimate = estimatedRpcsPerCol * 2;
           }
 
-          testSpecificScanRowSize(stmt, NODE_YB_SEQ_SCAN, select, where, ssEstimate, N_ROWS);
+          testSpecificScanRowSize(stmt, NODE_SEQ_SCAN, select, where, ssEstimate, N_ROWS);
           testSpecificScanRowSize(stmt, NODE_INDEX_ONLY_SCAN, select, where,
                                   iosEstimate, N_ROWS);
           if (nConditionCols > 0)
@@ -166,9 +153,9 @@ public void testScanRowSizeHashCode() throws Exception {
         if (nSelectedCols == 0) {
           ssEstimateWithoutCond = estimatedRpcsPerCol * 6;
         }
-        testSpecificScanRowSize(stmt, NODE_YB_SEQ_SCAN, select, hashcodeCond,
+        testSpecificScanRowSize(stmt, NODE_SEQ_SCAN, select, hashcodeCond,
                                 ssEstimateWithCond, N_ROWS_MATCHING_COND);
-        testSpecificScanRowSize(stmt, NODE_YB_SEQ_SCAN, select, "",
+        testSpecificScanRowSize(stmt, NODE_SEQ_SCAN, select, "",
                                 ssEstimateWithoutCond, N_ROWS);
       }
 
@@ -190,7 +177,7 @@ public void testScanRowSizeHashCode() throws Exception {
         }
         testSpecificScanRowSize(stmt, NODE_INDEX_ONLY_SCAN, select, hashcodeCond,
                                 iosEstimateWithCond, N_ROWS_MATCHING_COND);
-        testSpecificScanRowSize(stmt, NODE_YB_SEQ_SCAN, select, "",
+        testSpecificScanRowSize(stmt, NODE_SEQ_SCAN, select, "",
                                 iosEstimateWithoutCond, N_ROWS);
       }
     }
@@ -200,7 +187,7 @@ private void testSpecificScanRowSize(Statement stmt, String scanType, String sel
         String conditions, long expected, int expectedRows) throws Exception {
     String hint;
     switch(scanType) {
-      case NODE_YB_SEQ_SCAN:
+      case NODE_SEQ_SCAN:
         hint = "SeqScan(t)";
         break;
       case NODE_INDEX_ONLY_SCAN:

java/yb-pgsql/src/test/java/org/yb/pgsql/TestPgExplainAnalyzeScans.java

@@ -3,7 +3,6 @@
 import static org.yb.pgsql.ExplainAnalyzeUtils.NODE_INDEX_SCAN;
 import static org.yb.pgsql.ExplainAnalyzeUtils.NODE_INDEX_ONLY_SCAN;
 import static org.yb.pgsql.ExplainAnalyzeUtils.NODE_SEQ_SCAN;
-import static org.yb.pgsql.ExplainAnalyzeUtils.NODE_YB_SEQ_SCAN;
 
 import java.sql.Statement;
 
@@ -140,8 +139,8 @@ public void testYbSeqScan() throws Exception {
     final String queryWithExpr = String.format("/*+ SeqScan(foo) */ SELECT * FROM %s "
       + "WHERE v5 < 64", MAIN_TABLE);
 
-    PlanCheckerBuilder YB_SEQ_SCAN_PLAN = makePlanBuilder()
-        .nodeType(NODE_YB_SEQ_SCAN)
+    PlanCheckerBuilder SEQ_SCAN_PLAN = makePlanBuilder()
+        .nodeType(NODE_SEQ_SCAN)
         .relationName(MAIN_TABLE)
         .alias(MAIN_TABLE)
         .storageTableReadExecutionTime(Checkers.greater(0.0));
@@ -150,7 +149,7 @@ public void testYbSeqScan() throws Exception {
     Checker checker = SCAN_TOP_LEVEL_CHECKER
         .storageReadRequests(Checkers.equal(NUM_PAGES + 1))
         .storageReadExecutionTime(Checkers.greater(0.0))
-        .plan(YB_SEQ_SCAN_PLAN
+        .plan(SEQ_SCAN_PLAN
             .storageTableReadRequests(Checkers.equal(NUM_PAGES + 1))
             .build())
         .build();
@@ -161,7 +160,7 @@ public void testYbSeqScan() throws Exception {
     Checker pushdown_checker = SCAN_TOP_LEVEL_CHECKER
         .storageReadRequests(Checkers.equal(3))
         .storageReadExecutionTime(Checkers.greater(0.0))
-        .plan(YB_SEQ_SCAN_PLAN
+        .plan(SEQ_SCAN_PLAN
             .storageTableReadRequests(Checkers.equal(3))
             .build())
         .build();
@@ -172,7 +171,7 @@ public void testYbSeqScan() throws Exception {
     Checker no_pushdown_checker = SCAN_TOP_LEVEL_CHECKER
         .storageReadRequests(Checkers.equal(NUM_PAGES + 1))
         .storageReadExecutionTime(Checkers.greater(0.0))
-        .plan(YB_SEQ_SCAN_PLAN
+        .plan(SEQ_SCAN_PLAN
             .storageTableReadRequests(Checkers.equal(NUM_PAGES + 1))
             .build())
         .build();

java/yb-pgsql/src/test/java/org/yb/pgsql/TestPgPrefetchControl.java

@@ -23,8 +23,6 @@
 import java.sql.SQLException;
 import java.sql.Statement;
 import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.Collections;
 import java.util.List;
 
 import static org.yb.AssertionWrappers.assertEquals;
@@ -34,7 +32,6 @@
 import static org.yb.pgsql.ExplainAnalyzeUtils.NODE_LIMIT;
 import static org.yb.pgsql.ExplainAnalyzeUtils.NODE_SEQ_SCAN;
 import static org.yb.pgsql.ExplainAnalyzeUtils.NODE_YB_BATCHED_NESTED_LOOP;
-import static org.yb.pgsql.ExplainAnalyzeUtils.NODE_YB_SEQ_SCAN;
 
 import org.yb.util.json.Checker;
 import org.yb.util.json.Checkers;
@@ -87,13 +84,9 @@ public void testSimplePrefetch() throws Exception {
         tableName, tableRowCount - 1));
 
       String seqScanQuery = String.format("SELECT * FROM %s", tableName);
-      String ybSeqScanQuery = String.format("/*+ SeqScan(%s) */ SELECT * FROM %s",
-                                            tableName, tableName);
 
       checkReadRequests(statement, seqScanQuery, NODE_SEQ_SCAN,
                         Checkers.equal(51), tableRowCount);
-      checkReadRequests(statement, ybSeqScanQuery, NODE_YB_SEQ_SCAN,
-                        Checkers.equal(51), tableRowCount);
     }
   }
 
@@ -121,16 +114,12 @@ public void testSizeBasedFetch() throws Exception {
       statement.execute(String.format("create index on %s (v asc)", tableName));
 
       String seqScanQuery = String.format("SELECT * FROM %s", tableName);
-      String ybSeqScanQuery = String.format("/*+ SeqScan(%s) */ SELECT * FROM %s",
-                                            tableName, tableName);
       String indexScanQuery = String.format("SELECT * FROM %s WHERE k > 0", tableName);
       String indexOnlyScanQuery = String.format("SELECT v FROM %s WHERE v > ''", tableName);
 
       setRowAndSizeLimit(statement, 1024, 0);
       checkReadRequests(statement, seqScanQuery, NODE_SEQ_SCAN,
                         Checkers.equal(98), tableRowCount);
-      checkReadRequests(statement, ybSeqScanQuery, NODE_YB_SEQ_SCAN,
-                        Checkers.equal(98), tableRowCount);
       checkReadRequests(statement, indexScanQuery, NODE_INDEX_SCAN,
                         Checkers.equal(98), tableRowCount);
       checkReadRequests(statement, indexOnlyScanQuery, NODE_INDEX_ONLY_SCAN,
@@ -139,8 +128,6 @@ public void testSizeBasedFetch() throws Exception {
       setRowAndSizeLimit(statement, 0, 0);
       checkReadRequests(statement, seqScanQuery, NODE_SEQ_SCAN,
                         Checkers.equal(1), tableRowCount);
-      checkReadRequests(statement, ybSeqScanQuery, NODE_YB_SEQ_SCAN,
-                        Checkers.equal(1), tableRowCount);
       checkReadRequests(statement, indexScanQuery, NODE_INDEX_SCAN,
                         Checkers.equal(1), tableRowCount);
       checkReadRequests(statement, indexOnlyScanQuery, NODE_INDEX_ONLY_SCAN,
@@ -150,8 +137,6 @@ public void testSizeBasedFetch() throws Exception {
       setRowAndSizeLimit(statement, 0, 512);
       checkReadRequests(statement, seqScanQuery, NODE_SEQ_SCAN,
                         Checkers.equal(25), tableRowCount);
-      checkReadRequests(statement, ybSeqScanQuery, NODE_YB_SEQ_SCAN,
-                        Checkers.equal(25), tableRowCount);
       checkReadRequests(statement, indexScanQuery, NODE_INDEX_SCAN,
                         Checkers.equal(25), tableRowCount);
       checkReadRequests(statement, indexOnlyScanQuery, NODE_INDEX_ONLY_SCAN,
@@ -160,8 +145,6 @@ public void testSizeBasedFetch() throws Exception {
       setRowAndSizeLimit(statement, 0, 1024);
       checkReadRequests(statement, seqScanQuery, NODE_SEQ_SCAN,
                         Checkers.equal(13), tableRowCount);
-      checkReadRequests(statement, ybSeqScanQuery, NODE_YB_SEQ_SCAN,
-                        Checkers.equal(13), tableRowCount);
       checkReadRequests(statement, indexScanQuery, NODE_INDEX_SCAN,
                         Checkers.equal(13), tableRowCount);
       checkReadRequests(statement, indexOnlyScanQuery, NODE_INDEX_ONLY_SCAN,

java/yb-pgsql/src/test/java/org/yb/pgsql/TestYbBackup.java

@@ -1715,7 +1715,7 @@ public void testPgHintPlan() throws Exception {
                    " VALUES ('EXPLAIN (COSTS false) SELECT * FROM tbl1 WHERE tbl1.k = ?'," +
                    " '', 'SeqScan(tbl1)')");
       assertQuery(stmt, "EXPLAIN (COSTS false) SELECT * FROM tbl1 WHERE tbl1.k = 1",
-                  new Row("YB Seq Scan on tbl1"),
+                  new Row("Seq Scan on tbl1"),
                   new Row("  Remote Filter: (k = 1)"));
       stmt.execute("SET pg_hint_plan.enable_hint_table = off");
       assertQuery(stmt, "EXPLAIN (COSTS false) SELECT * FROM tbl1 WHERE tbl1.k = 1",
@@ -1738,10 +1738,10 @@ public void testPgHintPlan() throws Exception {
                    " '', 'SeqScan(tbl2)')");
       stmt.execute("SET pg_hint_plan.enable_hint_table = on");
       assertQuery(stmt, "EXPLAIN (COSTS false) SELECT * FROM tbl1 WHERE tbl1.k = 1",
-                  new Row("YB Seq Scan on tbl1"),
+                  new Row("Seq Scan on tbl1"),
                   new Row("  Remote Filter: (k = 1)"));
       assertQuery(stmt, "EXPLAIN (COSTS false) SELECT * FROM tbl2 WHERE tbl2.k = 3",
-                  new Row("YB Seq Scan on tbl2"),
+                  new Row("Seq Scan on tbl2"),
                   new Row("  Remote Filter: (k = 3)"));
       stmt.execute("SET pg_hint_plan.enable_hint_table = off");
       assertQuery(stmt, "EXPLAIN (COSTS false) SELECT * FROM tbl1 WHERE tbl1.k = 1",

src/postgres/src/backend/commands/explain.c

@@ -1307,7 +1307,7 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			pname = sname = "Seq Scan";
 			break;
 		case T_YbSeqScan:
-			pname = sname = "YB Seq Scan";
+			pname = sname = "Seq Scan";
 			break;
 		case T_SampleScan:
 			pname = sname = "Sample Scan";
@@ -1365,7 +1365,7 @@ ExplainNode(PlanState *planstate, List *ancestors,
 				case CMD_SELECT:
 					/* Don't need to expose implementation details */
 					if (IsYBRelation(((ScanState*) planstate)->ss_currentRelation))
-						sname = pname = "Seq Scan";
+						sname = pname = "YB Foreign Scan";
 					else
 						pname = "Foreign Scan";
 					operation = "Select";

src/postgres/src/backend/optimizer/path/allpaths.c

@@ -525,19 +525,7 @@ set_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
 				else
 				{
 					/* Plain relation */
-					if (IsYBRelationById(rte->relid))
-					{
-						/*
-						 * Using a foreign scan which will use the YB FDW by
-						 * default.
-						 */
-						set_foreign_pathlist(root, rel, rte);
-					}
-					else
-					{
-						/* Use regular scan for initdb tables. */
-						set_plain_rel_pathlist(root, rel, rte);
-					}
+					set_plain_rel_pathlist(root, rel, rte);
 				}
 				break;
 			case RTE_SUBQUERY: