Refactor COPY FROM to use format callback functions.

This commit introduces a new CopyFromRoutine struct, which is a set of
callback routines to read tuples in a specific format. It also makes
COPY FROM with the existing formats (text, CSV, and binary) utilize
these format callbacks.

This change is a preliminary step towards making the COPY FROM command
extensible in terms of input formats.

Similar to 2e4127b, this refactoring contributes to a performance
improvement by reducing the number of "if" branches that need to be
checked on a per-row basis when sending field representations in text
or CSV mode. The performance benchmark results showed ~5% performance
gain in text or CSV mode.

Author: Sutou Kouhei <kou@clear-code.com>
Reviewed-by: Masahiko Sawada <sawada.mshk@gmail.com>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Reviewed-by: Andres Freund <andres@anarazel.de>
Reviewed-by: Tomas Vondra <tomas.vondra@enterprisedb.com>
Reviewed-by: Junwang Zhao <zhjwpku@gmail.com>
Discussion: https://postgr.es/m/20231204.153548.2126325458835528809.kou@clear-code.com

Author: MasahikoSawada

src/backend/commands/copyfrom.c

@@ -28,7 +28,7 @@
 #include "access/tableam.h"
 #include "access/xact.h"
 #include "catalog/namespace.h"
-#include "commands/copy.h"
+#include "commands/copyapi.h"
 #include "commands/copyfrom_internal.h"
 #include "commands/progress.h"
 #include "commands/trigger.h"
@@ -106,6 +106,145 @@ typedef struct CopyMultiInsertInfo
 /* non-export function prototypes */
 static void ClosePipeFromProgram(CopyFromState cstate);
 
+/*
+ * Built-in format-specific routines. One-row callbacks are defined in
+ * copyfromparse.c.
+ */
+static void CopyFromTextLikeInFunc(CopyFromState cstate, Oid atttypid, FmgrInfo *finfo,
+								   Oid *typioparam);
+static void CopyFromTextLikeStart(CopyFromState cstate, TupleDesc tupDesc);
+static void CopyFromTextLikeEnd(CopyFromState cstate);
+static void CopyFromBinaryInFunc(CopyFromState cstate, Oid atttypid,
+								 FmgrInfo *finfo, Oid *typioparam);
+static void CopyFromBinaryStart(CopyFromState cstate, TupleDesc tupDesc);
+static void CopyFromBinaryEnd(CopyFromState cstate);
+
+
+/*
+ * COPY FROM routines for built-in formats.
+ *
+ * CSV and text formats share the same TextLike routines except for the
+ * one-row callback.
+ */
+
+/* text format */
+static const CopyFromRoutine CopyFromRoutineText = {
+	.CopyFromInFunc = CopyFromTextLikeInFunc,
+	.CopyFromStart = CopyFromTextLikeStart,
+	.CopyFromOneRow = CopyFromTextOneRow,
+	.CopyFromEnd = CopyFromTextLikeEnd,
+};
+
+/* CSV format */
+static const CopyFromRoutine CopyFromRoutineCSV = {
+	.CopyFromInFunc = CopyFromTextLikeInFunc,
+	.CopyFromStart = CopyFromTextLikeStart,
+	.CopyFromOneRow = CopyFromCSVOneRow,
+	.CopyFromEnd = CopyFromTextLikeEnd,
+};
+
+/* binary format */
+static const CopyFromRoutine CopyFromRoutineBinary = {
+	.CopyFromInFunc = CopyFromBinaryInFunc,
+	.CopyFromStart = CopyFromBinaryStart,
+	.CopyFromOneRow = CopyFromBinaryOneRow,
+	.CopyFromEnd = CopyFromBinaryEnd,
+};
+
+/* Return a COPY FROM routine for the given options */
+static const CopyFromRoutine *
+CopyFromGetRoutine(CopyFormatOptions opts)
+{
+	if (opts.csv_mode)
+		return &CopyFromRoutineCSV;
+	else if (opts.binary)
+		return &CopyFromRoutineBinary;
+
+	/* default is text */
+	return &CopyFromRoutineText;
+}
+
+/* Implementation of the start callback for text and CSV formats */
+static void
+CopyFromTextLikeStart(CopyFromState cstate, TupleDesc tupDesc)
+{
+	AttrNumber	attr_count;
+
+	/*
+	 * If encoding conversion is needed, we need another buffer to hold the
+	 * converted input data.  Otherwise, we can just point input_buf to the
+	 * same buffer as raw_buf.
+	 */
+	if (cstate->need_transcoding)
+	{
+		cstate->input_buf = (char *) palloc(INPUT_BUF_SIZE + 1);
+		cstate->input_buf_index = cstate->input_buf_len = 0;
+	}
+	else
+		cstate->input_buf = cstate->raw_buf;
+	cstate->input_reached_eof = false;
+
+	initStringInfo(&cstate->line_buf);
+
+	/*
+	 * Create workspace for CopyReadAttributes results; used by CSV and text
+	 * format.
+	 */
+	attr_count = list_length(cstate->attnumlist);
+	cstate->max_fields = attr_count;
+	cstate->raw_fields = (char **) palloc(attr_count * sizeof(char *));
+}
+
+/*
+ * Implementation of the infunc callback for text and CSV formats. Assign
+ * the input function data to the given *finfo.
+ */
+static void
+CopyFromTextLikeInFunc(CopyFromState cstate, Oid atttypid, FmgrInfo *finfo,
+					   Oid *typioparam)
+{
+	Oid			func_oid;
+
+	getTypeInputInfo(atttypid, &func_oid, typioparam);
+	fmgr_info(func_oid, finfo);
+}
+
+/* Implementation of the end callback for text and CSV formats */
+static void
+CopyFromTextLikeEnd(CopyFromState cstate)
+{
+	/* nothing to do */
+}
+
+/* Implementation of the start callback for binary format */
+static void
+CopyFromBinaryStart(CopyFromState cstate, TupleDesc tupDesc)
+{
+	/* Read and verify binary header */
+	ReceiveCopyBinaryHeader(cstate);
+}
+
+/*
+ * Implementation of the infunc callback for binary format. Assign
+ * the binary input function to the given *finfo.
+ */
+static void
+CopyFromBinaryInFunc(CopyFromState cstate, Oid atttypid,
+					 FmgrInfo *finfo, Oid *typioparam)
+{
+	Oid			func_oid;
+
+	getTypeBinaryInputInfo(atttypid, &func_oid, typioparam);
+	fmgr_info(func_oid, finfo);
+}
+
+/* Implementation of the end callback for binary format */
+static void
+CopyFromBinaryEnd(CopyFromState cstate)
+{
+	/* nothing to do */
+}
+
 /*
  * error context callback for COPY FROM
  *
@@ -1403,7 +1542,6 @@ BeginCopyFrom(ParseState *pstate,
 				num_defaults;
 	FmgrInfo   *in_functions;
 	Oid		   *typioparams;
-	Oid			in_func_oid;
 	int		   *defmap;
 	ExprState **defexprs;
 	MemoryContext oldcontext;
@@ -1435,6 +1573,9 @@ BeginCopyFrom(ParseState *pstate,
 	/* Extract options from the statement node tree */
 	ProcessCopyOptions(pstate, &cstate->opts, true /* is_from */ , options);
 
+	/* Set the format routine */
+	cstate->routine = CopyFromGetRoutine(cstate->opts);
+
 	/* Process the target relation */
 	cstate->rel = rel;
 
@@ -1590,25 +1731,6 @@ BeginCopyFrom(ParseState *pstate,
 	cstate->raw_buf_index = cstate->raw_buf_len = 0;
 	cstate->raw_reached_eof = false;
 
-	if (!cstate->opts.binary)
-	{
-		/*
-		 * If encoding conversion is needed, we need another buffer to hold
-		 * the converted input data.  Otherwise, we can just point input_buf
-		 * to the same buffer as raw_buf.
-		 */
-		if (cstate->need_transcoding)
-		{
-			cstate->input_buf = (char *) palloc(INPUT_BUF_SIZE + 1);
-			cstate->input_buf_index = cstate->input_buf_len = 0;
-		}
-		else
-			cstate->input_buf = cstate->raw_buf;
-		cstate->input_reached_eof = false;
-
-		initStringInfo(&cstate->line_buf);
-	}
-
 	initStringInfo(&cstate->attribute_buf);
 
 	/* Assign range table and rteperminfos, we'll need them in CopyFrom. */
@@ -1641,13 +1763,9 @@ BeginCopyFrom(ParseState *pstate,
 			continue;
 
 		/* Fetch the input function and typioparam info */
-		if (cstate->opts.binary)
-			getTypeBinaryInputInfo(att->atttypid,
-								   &in_func_oid, &typioparams[attnum - 1]);
-		else
-			getTypeInputInfo(att->atttypid,
-							 &in_func_oid, &typioparams[attnum - 1]);
-		fmgr_info(in_func_oid, &in_functions[attnum - 1]);
+		cstate->routine->CopyFromInFunc(cstate, att->atttypid,
+										&in_functions[attnum - 1],
+										&typioparams[attnum - 1]);
 
 		/* Get default info if available */
 		defexprs[attnum - 1] = NULL;
@@ -1782,20 +1900,7 @@ BeginCopyFrom(ParseState *pstate,
 
 	pgstat_progress_update_multi_param(3, progress_cols, progress_vals);
 
-	if (cstate->opts.binary)
-	{
-		/* Read and verify binary header */
-		ReceiveCopyBinaryHeader(cstate);
-	}
-
-	/* create workspace for CopyReadAttributes results */
-	if (!cstate->opts.binary)
-	{
-		AttrNumber	attr_count = list_length(cstate->attnumlist);
-
-		cstate->max_fields = attr_count;
-		cstate->raw_fields = (char **) palloc(attr_count * sizeof(char *));
-	}
+	cstate->routine->CopyFromStart(cstate, tupDesc);
 
 	MemoryContextSwitchTo(oldcontext);
 
@@ -1808,6 +1913,9 @@ BeginCopyFrom(ParseState *pstate,
 void
 EndCopyFrom(CopyFromState cstate)
 {
+	/* Invoke the end callback */
+	cstate->routine->CopyFromEnd(cstate);
+
 	/* No COPY FROM related resources except memory. */
 	if (cstate->is_program)
 	{