From ec1e277e8ee7bb57b66e57476a8c707e33bec7a9 Mon Sep 17 00:00:00 2001
From: Hadi Moshayedi <hadi@moshayedi.net>
Date: Sat, 26 Sep 2020 23:50:23 -0700
Subject: [PATCH] Initial implementation of ANALYZE

---
 Makefile         |  4 ++--
 cstore_tableam.c | 27 ++++++++++++++++++++++++---
 2 files changed, 26 insertions(+), 5 deletions(-)

diff --git a/Makefile b/Makefile
index ea5a858bf..483aebc35 100644
--- a/Makefile
+++ b/Makefile
@@ -48,11 +48,11 @@ ifeq ($(USE_FDW),yes)
 		   fdw_copyto fdw_alter fdw_truncate fdw_clean
 endif
 
-# disabled tests: am_block_filtering am_analyze
+# disabled tests: am_block_filtering
 ifeq ($(USE_TABLEAM),yes)
 	PG_CFLAGS += -DUSE_TABLEAM
 	OBJS += cstore_tableam.o
-	REGRESS += am_create am_load am_query am_data_types am_functions \
+	REGRESS += am_create am_load am_query am_analyze am_data_types am_functions \
 	           am_drop am_insert am_copyto am_alter am_truncate am_clean
 endif
 
diff --git a/cstore_tableam.c b/cstore_tableam.c
index 312e10981..3f8c37db9 100644
--- a/cstore_tableam.c
+++ b/cstore_tableam.c
@@ -470,8 +470,13 @@ static bool
 cstore_scan_analyze_next_block(TableScanDesc scan, BlockNumber blockno,
 							   BufferAccessStrategy bstrategy)
 {
-	/* TODO */
-	return false;
+	/*
+	 * Our access method is not pages based, i.e. tuples are not confined
+	 * to pages boundaries. So not much to do here. We return true anyway
+	 * so acquire_sample_rows() in analyze.c would call our
+	 * cstore_scan_analyze_next_tuple() callback.
+	 */
+	return true;
 }
 
 
@@ -480,7 +485,23 @@ cstore_scan_analyze_next_tuple(TableScanDesc scan, TransactionId OldestXmin,
 							   double *liverows, double *deadrows,
 							   TupleTableSlot *slot)
 {
-	/* TODO */
+	/*
+	 * Currently we don't do anything smart to reduce number of rows returned
+	 * for ANALYZE. The TableAM API's ANALYZE functions are designed for page
+	 * based access methods where it chooses random pages, and then reads
+	 * tuples from those pages.
+	 *
+	 * We could do something like that here by choosing sample stripes or blocks,
+	 * but getting that correct might need quite some work. Since cstore_fdw's
+	 * ANALYZE scanned all rows, as a starter we do the same here and scan all
+	 * rows.
+	 */
+	if (cstore_getnextslot(scan, ForwardScanDirection, slot))
+	{
+		(*liverows)++;
+		return true;
+	}
+
 	return false;
 }