Subject: [PATCH v27 5/9] Add support for implementing custom COPY TO format as extension

From: Sutou Kouhei <[email-masked]>
Date: Mon, 25 Nov 2024 14:01:18 +0900

* Add CopyToStateData::opaque that can be used to keep data for custom
  COPY TO format implementation
* Export CopySendEndOfRow() to flush data in CopyToStateData::fe_msgbuf
  as CopyToStateFlush()
---
 src/backend/commands/copyto.c  | 12 ++++++++++++
 src/include/commands/copyapi.h |  5 +++++
 2 files changed, 17 insertions(+)

diff --git a/src/backend/commands/copyto.c b/src/backend/commands/copyto.c
index 96b5e144a1d..cb9bfa0053f 100644
--- a/src/backend/commands/copyto.c
+++ b/src/backend/commands/copyto.c
@@ -442,6 +442,18 @@ CopySendEndOfRow(CopyToState cstate)
 	resetStringInfo(fe_msgbuf);
 }
 
+/*
+ * Export CopySendEndOfRow() for extensions. We want to keep
+ * CopySendEndOfRow() as a static function for
+ * optimization. CopySendEndOfRow() calls in this file may be optimized by a
+ * compiler.
+ */
+void
+CopyToStateFlush(CopyToState cstate)
+{
+	CopySendEndOfRow(cstate);
+}
+
 /*
  * Wrapper function of CopySendEndOfRow for text and CSV formats. Sends the
  * the line termination and do common appropriate things for the end of row.
diff --git a/src/include/commands/copyapi.h b/src/include/commands/copyapi.h
index 1cb2815deab..030a82aca7f 100644
--- a/src/include/commands/copyapi.h
+++ b/src/include/commands/copyapi.h
@@ -116,8 +116,13 @@ typedef struct CopyToStateData
 	FmgrInfo   *out_functions;	/* lookup info for output functions */
 	MemoryContext rowcontext;	/* per-row evaluation context */
 	uint64		bytes_processed;	/* number of bytes processed so far */
+
+	/* For custom format implementation */
+	void	   *opaque;			/* private space */
 } CopyToStateData;
 
+extern void CopyToStateFlush(CopyToState cstate);
+
 /*
  * API structure for a COPY FROM format implementation.	 Note this must be
  * allocated in a server-lifetime manner, typically as a static const struct.
-- 
2.45.2

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