pgstat: split different types of stats into separate files.

pgstat.c is very long, and it's hard to find an order that makes sense and is
likely to be maintained over time. Splitting the different pieces into
separate files makes that a lot easier.

With a few exceptions, this commit just moves code around. Those exceptions
are:
- adding file headers for new files
- removing 'static' from functions
- adapting pgstat_assert_is_up() to work across TUs
- minor comment adjustments
git diff --color-moved=dimmed-zebra is very helpful separating code movement
from code changes.

The next commit in this series will reorder pgstat.[ch] contents to be a bit
more coherent.

Earlier revisions of this patch had "global" statistics (archiver, bgwriter,
checkpointer, replication slots, SLRU, WAL) in one file, because each seemed
small enough. However later commits will increase their size and their
aggregate size is not insubstantial. It also just seems easier to split each
type of statistic into its own file.

Author: Andres Freund <[email protected]>
Discussion: https://postgr.es/m/[email protected]

1 files changed, 161 insertions, 0 deletions

diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
new file mode 100644
index 00000000000..abbb4f8d964
--- /dev/null
+++ b/src/include/utils/pgstat_internal.h
@@ -0,0 +1,161 @@
+/* ----------
+ * pgstat_internal.h
+ *
+ * Definitions for the PostgreSQL activity statistics facility that should
+ * only be needed by files implementing statistics support (rather than ones
+ * reporting / querying stats).
+ *
+ * Copyright (c) 2001-2022, PostgreSQL Global Development Group
+ *
+ * src/include/utils/pgstat_internal.h
+ * ----------
+ */
+#ifndef PGSTAT_INTERNAL_H
+#define PGSTAT_INTERNAL_H
+
+
+#include "pgstat.h"
+
+
+#define PGSTAT_STAT_INTERVAL	500 /* Minimum time between stats file
+									 * updates; in milliseconds. */
+
+/* ----------
+ * The initial size hints for the hash tables used in the collector.
+ * ----------
+ */
+#define PGSTAT_DB_HASH_SIZE		16
+#define PGSTAT_TAB_HASH_SIZE	512
+#define PGSTAT_FUNCTION_HASH_SIZE	512
+#define PGSTAT_SUBSCRIPTION_HASH_SIZE	32
+#define PGSTAT_REPLSLOT_HASH_SIZE	32
+
+
+/*
+ * Some stats changes are transactional. To maintain those, a stack of
+ * PgStat_SubXactStatus entries is maintained, which contain data pertaining
+ * to the current transaction and its active subtransactions.
+ */
+typedef struct PgStat_SubXactStatus
+{
+	int			nest_level;		/* subtransaction nest level */
+
+	struct PgStat_SubXactStatus *prev;	/* higher-level subxact if any */
+
+	/*
+	 * Tuple insertion/deletion counts for an open transaction can't be
+	 * propagated into PgStat_TableStatus counters until we know if it is
+	 * going to commit or abort.  Hence, we keep these counts in per-subxact
+	 * structs that live in TopTransactionContext.  This data structure is
+	 * designed on the assumption that subxacts won't usually modify very many
+	 * tables.
+	 */
+	PgStat_TableXactStatus *first;	/* head of list for this subxact */
+} PgStat_SubXactStatus;
+
+
+/*
+ * List of SLRU names that we keep stats for.  There is no central registry of
+ * SLRUs, so we use this fixed list instead.  The "other" entry is used for
+ * all SLRUs without an explicit entry (e.g. SLRUs in extensions).
+ */
+static const char *const slru_names[] = {
+	"CommitTs",
+	"MultiXactMember",
+	"MultiXactOffset",
+	"Notify",
+	"Serial",
+	"Subtrans",
+	"Xact",
+	"other"						/* has to be last */
+};
+
+#define SLRU_NUM_ELEMENTS	lengthof(slru_names)
+
+
+/*
+ * Functions in pgstat.c
+ */
+
+extern PgStat_SubXactStatus *pgstat_xact_stack_level_get(int nest_level);
+extern void pgstat_setheader(PgStat_MsgHdr *hdr, StatMsgType mtype);
+extern void pgstat_send(void *msg, int len);
+#ifdef USE_ASSERT_CHECKING
+extern void pgstat_assert_is_up(void);
+#else
+#define pgstat_assert_is_up() ((void)true)
+#endif
+
+
+/*
+ * Functions in pgstat_database.c
+ */
+
+extern void AtEOXact_PgStat_Database(bool isCommit, bool parallel);
+extern void pgstat_report_disconnect(Oid dboid);
+extern void pgstat_update_dbstats(PgStat_MsgTabstat *tsmsg, TimestampTz now);
+
+
+/*
+ * Functions in pgstat_function.c
+ */
+
+extern void pgstat_send_funcstats(void);
+
+
+/*
+ * Functions in pgstat_relation.c
+ */
+
+extern void AtEOXact_PgStat_Relations(PgStat_SubXactStatus *xact_state, bool isCommit);
+extern void AtEOSubXact_PgStat_Relations(PgStat_SubXactStatus *xact_state, bool isCommit, int nestDepth);
+extern void AtPrepare_PgStat_Relations(PgStat_SubXactStatus *xact_state);
+extern void PostPrepare_PgStat_Relations(PgStat_SubXactStatus *xact_state);
+extern void pgstat_send_tabstats(TimestampTz now, bool disconnect);
+
+
+/*
+ * Functions in pgstat_slru.c
+ */
+
+extern void pgstat_send_slru(void);
+
+
+/*
+ * Functions in pgstat_wal.c
+ */
+
+extern void pgstat_wal_initialize(void);
+extern bool pgstat_wal_pending(void);
+
+
+/*
+ * Variables in pgstat.c
+ */
+
+extern pgsocket pgStatSock;
+
+
+/*
+ * Variables in pgstat_database.c
+ */
+
+extern int	pgStatXactCommit;
+extern int	pgStatXactRollback;
+
+
+/*
+ * Variables in pgstat_functions.c
+ */
+
+extern bool have_function_stats;
+
+
+/*
+ * Variables in pgstat_relation.c
+ */
+
+extern bool have_relation_stats;
+
+
+#endif							/* PGSTAT_INTERNAL_H */