Columnar: few fixes (#4371)

* Columnar: fix a memory issue

* Columnar: no need for deferred triggers

* Columnar: relax memory growth constraints

src/backend/columnar/cstore_writer.c

@@ -112,7 +112,7 @@ CStoreBeginWrite(RelFileNode relfilenode,
 	writeState->stripeWriteContext = stripeWriteContext;
 	writeState->blockData = blockData;
 	writeState->compressionBuffer = NULL;
-	writeState->perTupleContext = AllocSetContextCreate(stripeWriteContext,
+	writeState->perTupleContext = AllocSetContextCreate(CurrentMemoryContext,
 														"CStore per tuple context",
 														ALLOCSET_DEFAULT_SIZES);
 

src/backend/columnar/sql/columnar--9.5-1--10.0-1.sql

@@ -42,7 +42,7 @@ CREATE TABLE cstore_skipnodes (
     exists_stream_length bigint NOT NULL,
     value_compression_type int NOT NULL,
     PRIMARY KEY (storageid, stripe, attr, block),
-    FOREIGN KEY (storageid, stripe) REFERENCES cstore_stripes(storageid, stripe) ON DELETE CASCADE INITIALLY DEFERRED
+    FOREIGN KEY (storageid, stripe) REFERENCES cstore_stripes(storageid, stripe) ON DELETE CASCADE
 ) WITH (user_catalog_table = true);
 
 COMMENT ON TABLE cstore_skipnodes IS 'CStore per block metadata';

src/test/regress/expected/am_memory.out

@@ -81,7 +81,7 @@ write_clear_outside_xact | t
 INSERT INTO t
  SELECT i, 'last batch', 0 /* no need to record memusage per row */
  FROM generate_series(1, 50000) i;
-SELECT 1.0 * TopMemoryContext / :top_post BETWEEN 0.99 AND 1.01 AS top_growth_ok
+SELECT 1.0 * TopMemoryContext / :top_post BETWEEN 0.98 AND 1.02 AS top_growth_ok
 FROM column_store_memory_stats();
 -[ RECORD 1 ]-+--
 top_growth_ok | t

src/test/regress/sql/am_memory.sql

@@ -85,7 +85,7 @@ INSERT INTO t
  SELECT i, 'last batch', 0 /* no need to record memusage per row */
  FROM generate_series(1, 50000) i;
 
-SELECT 1.0 * TopMemoryContext / :top_post BETWEEN 0.99 AND 1.01 AS top_growth_ok
+SELECT 1.0 * TopMemoryContext / :top_post BETWEEN 0.98 AND 1.02 AS top_growth_ok
 FROM column_store_memory_stats();
 
 -- before this change, max mem usage while executing inserts was 28MB and