copy.c

/*
 * psql - the PostgreSQL interactive terminal
 *
 * Copyright (c) 2000-2024, PostgreSQL Global Development Group
 *
 * src/bin/psql/copy.c
 */
#include "postgres_fe.h"

#include <signal.h>
#include <sys/stat.h>
#ifndef WIN32
#include <unistd.h>				/* for isatty */
#else
#include <io.h>					/* I think */
#endif

#include "common.h"
#include "common/logging.h"
#include "copy.h"
#include "libpq-fe.h"
#include "pqexpbuffer.h"
#include "prompt.h"
#include "settings.h"
#include "stringutils.h"

/*
 * parse_slash_copy
 * -- parses \copy command line
 *
 * The documented syntax is:
 *	\copy tablename [(columnlist)] from|to filename [options]
 *	\copy ( query stmt ) to filename [options]
 *
 * where 'filename' can be one of the following:
 *	'<file path>' | PROGRAM '<command>' | stdin | stdout | pstdout | pstdout
 * and 'query' can be one of the following:
 *	SELECT | UPDATE | INSERT | DELETE
 *
 * An undocumented fact is that you can still write BINARY before the
 * tablename; this is a hangover from the pre-7.3 syntax.  The options
 * syntax varies across backend versions, but we avoid all that mess
 * by just transmitting the stuff after the filename literally.
 *
 * table name can be double-quoted and can have a schema part.
 * column names can be double-quoted.
 * filename can be single-quoted like SQL literals.
 * command must be single-quoted like SQL literals.
 *
 * returns a malloc'ed structure with the options, or NULL on parsing error
 */

struct copy_options
{
	char	   *before_tofrom;	/* COPY string before TO/FROM */
	char	   *after_tofrom;	/* COPY string after TO/FROM filename */
	char	   *file;			/* NULL = stdin/stdout */
	bool		program;		/* is 'file' a program to popen? */
	bool		psql_inout;		/* true = use psql stdin/stdout */
	bool		from;			/* true = FROM, false = TO */
};


static void
free_copy_options(struct copy_options *ptr)
{
	if (!ptr)
		return;
	free(ptr->before_tofrom);
	free(ptr->after_tofrom);
	free(ptr->file);
	free(ptr);
}


/* concatenate "more" onto "var", freeing the original value of *var */
static void
xstrcat(char **var, const char *more)
{
	char	   *newvar;

	newvar = psprintf("%s%s", *var, more);
	free(*var);
	*var = newvar;
}


static struct copy_options *
parse_slash_copy(const char *args)
{
	struct copy_options *result;
	char	   *token;
	const char *whitespace = " \t\n\r";
	char		nonstd_backslash = standard_strings() ? 0 : '\\';

	if (!args)
	{
		pg_log_error("\\copy: arguments required");
		return NULL;
	}

	result = pg_malloc0(sizeof(struct copy_options));

	result->before_tofrom = pg_strdup("");	/* initialize for appending */

	token = strtokx(args, whitespace, ".,()", "\"",
					0, false, false, pset.encoding);
	if (!token)
		goto error;

	/* The following can be removed when we drop 7.3 syntax support */
	if (pg_strcasecmp(token, "binary") == 0)
	{
		xstrcat(&result->before_tofrom, token);
		token = strtokx(NULL, whitespace, ".,()", "\"",
						0, false, false, pset.encoding);
		if (!token)
			goto error;
	}

	/* Handle COPY (query) case */
	if (token[0] == '(')
	{
		int			parens = 1;

		while (parens > 0)
		{
			xstrcat(&result->before_tofrom, " ");
			xstrcat(&result->before_tofrom, token);
			token = strtokx(NULL, whitespace, "()", "\"'",
							nonstd_backslash, true, false, pset.encoding);
			if (!token)
				goto error;
			if (token[0] == '(')
				parens++;
			else if (token[0] == ')')
				parens--;
		}
	}

	xstrcat(&result->before_tofrom, " ");
	xstrcat(&result->before_tofrom, token);
	token = strtokx(NULL, whitespace, ".,()", "\"",
					0, false, false, pset.encoding);
	if (!token)
		goto error;

	/*
	 * strtokx() will not have returned a multi-character token starting with
	 * '.', so we don't need strcmp() here.  Likewise for '(', etc, below.
	 */
	if (token[0] == '.')
	{
		/* handle schema . table */
		xstrcat(&result->before_tofrom, token);
		token = strtokx(NULL, whitespace, ".,()", "\"",
						0, false, false, pset.encoding);
		if (!token)
			goto error;
		xstrcat(&result->before_tofrom, token);
		token = strtokx(NULL, whitespace, ".,()", "\"",
						0, false, false, pset.encoding);
		if (!token)
			goto error;
	}

	if (token[0] == '(')
	{
		/* handle parenthesized column list */
		for (;;)
		{
			xstrcat(&result->before_tofrom, " ");
			xstrcat(&result->before_tofrom, token);
			token = strtokx(NULL, whitespace, "()", "\"",
							0, false, false, pset.encoding);
			if (!token)
				goto error;
			if (token[0] == ')')
				break;
		}
		xstrcat(&result->before_tofrom, " ");
		xstrcat(&result->before_tofrom, token);
		token = strtokx(NULL, whitespace, ".,()", "\"",
						0, false, false, pset.encoding);
		if (!token)
			goto error;
	}

	if (pg_strcasecmp(token, "from") == 0)
		result->from = true;
	else if (pg_strcasecmp(token, "to") == 0)
		result->from = false;
	else
		goto error;

	/* { 'filename' | PROGRAM 'command' | STDIN | STDOUT | PSTDIN | PSTDOUT } */
	token = strtokx(NULL, whitespace, ";", "'",
					0, false, false, pset.encoding);
	if (!token)
		goto error;

	if (pg_strcasecmp(token, "program") == 0)
	{
		int			toklen;

		token = strtokx(NULL, whitespace, ";", "'",
						0, false, false, pset.encoding);
		if (!token)
			goto error;

		/*
		 * The shell command must be quoted. This isn't fool-proof, but
		 * catches most quoting errors.
		 */
		toklen = strlen(token);
		if (token[0] != '\'' || toklen < 2 || token[toklen - 1] != '\'')
			goto error;

		strip_quotes(token, '\'', 0, pset.encoding);

		result->program = true;
		result->file = pg_strdup(token);
	}
	else if (pg_strcasecmp(token, "stdin") == 0 ||
			 pg_strcasecmp(token, "stdout") == 0)
	{
		result->file = NULL;
	}
	else if (pg_strcasecmp(token, "pstdin") == 0 ||
			 pg_strcasecmp(token, "pstdout") == 0)
	{
		result->psql_inout = true;
		result->file = NULL;
	}
	else
	{
		/* filename can be optionally quoted */
		strip_quotes(token, '\'', 0, pset.encoding);
		result->file = pg_strdup(token);
		expand_tilde(&result->file);
	}

	/* Collect the rest of the line (COPY options) */
	token = strtokx(NULL, "", NULL, NULL,
					0, false, false, pset.encoding);
	if (token)
		result->after_tofrom = pg_strdup(token);

	return result;

error:
	if (token)
		pg_log_error("\\copy: parse error at \"%s\"", token);
	else
		pg_log_error("\\copy: parse error at end of line");
	free_copy_options(result);

	return NULL;
}


/*
 * Execute a \copy command (frontend copy). We have to open a file (or execute
 * a command), then submit a COPY query to the backend and either feed it data
 * from the file or route its response into the file.
 */
bool
do_copy(const char *args)
{
	PQExpBufferData query;
	FILE	   *copystream;
	struct copy_options *options;
	bool		success;

	/* parse options */
	options = parse_slash_copy(args);

	if (!options)
		return false;

	/* prepare to read or write the target file */
	if (options->file && !options->program)
		canonicalize_path(options->file);

	if (options->from)
	{
		if (options->file)
		{
			if (options->program)
			{
				fflush(NULL);
				errno = 0;
				copystream = popen(options->file, PG_BINARY_R);
			}
			else
				copystream = fopen(options->file, PG_BINARY_R);
		}
		else if (!options->psql_inout)
			copystream = pset.cur_cmd_source;
		else
			copystream = stdin;
	}
	else
	{
		if (options->file)
		{
			if (options->program)
			{
				fflush(NULL);
				disable_sigpipe_trap();
				errno = 0;
				copystream = popen(options->file, PG_BINARY_W);
			}
			else
				copystream = fopen(options->file, PG_BINARY_W);
		}
		else if (!options->psql_inout)
			copystream = pset.queryFout;
		else
			copystream = stdout;
	}

	if (!copystream)
	{
		if (options->program)
			pg_log_error("could not execute command \"%s\": %m",
						 options->file);
		else
			pg_log_error("%s: %m",
						 options->file);
		free_copy_options(options);
		return false;
	}

	if (!options->program)
	{
		struct stat st;
		int			result;

		/* make sure the specified file is not a directory */
		if ((result = fstat(fileno(copystream), &st)) < 0)
			pg_log_error("could not stat file \"%s\": %m",
						 options->file);

		if (result == 0 && S_ISDIR(st.st_mode))
			pg_log_error("%s: cannot copy from/to a directory",
						 options->file);

		if (result < 0 || S_ISDIR(st.st_mode))
		{
			fclose(copystream);
			free_copy_options(options);
			return false;
		}
	}

	/* build the command we will send to the backend */
	initPQExpBuffer(&query);
	printfPQExpBuffer(&query, "COPY ");
	appendPQExpBufferStr(&query, options->before_tofrom);
	if (options->from)
		appendPQExpBufferStr(&query, " FROM STDIN ");
	else
		appendPQExpBufferStr(&query, " TO STDOUT ");
	if (options->after_tofrom)
		appendPQExpBufferStr(&query, options->after_tofrom);

	/* run it like a user command, but with copystream as data source/sink */
	pset.copyStream = copystream;
	success = SendQuery(query.data);
	pset.copyStream = NULL;
	termPQExpBuffer(&query);

	if (options->file != NULL)
	{
		if (options->program)
		{
			int			pclose_rc = pclose(copystream);

			if (pclose_rc != 0)
			{
				if (pclose_rc < 0)
					pg_log_error("could not close pipe to external command: %m");
				else
				{
					char	   *reason = wait_result_to_str(pclose_rc);

					pg_log_error("%s: %s", options->file,
								 reason ? reason : "");
					free(reason);
				}
				success = false;
			}
			SetShellResultVariables(pclose_rc);
			restore_sigpipe_trap();
		}
		else
		{
			if (fclose(copystream) != 0)
			{
				pg_log_error("%s: %m", options->file);
				success = false;
			}
		}
	}
	free_copy_options(options);
	return success;
}


/*
 * Functions for handling COPY IN/OUT data transfer.
 *
 * If you want to use COPY TO STDOUT/FROM STDIN in your application,
 * this is the code to steal ;)
 */

/*
 * handleCopyOut
 * receives data as a result of a COPY ... TO STDOUT command
 *
 * conn should be a database connection that you just issued COPY TO on
 * and got back a PGRES_COPY_OUT result.
 *
 * copystream is the file stream for the data to go to.
 * copystream can be NULL to eat the data without writing it anywhere.
 *
 * The final status for the COPY is returned into *res (but note
 * we already reported the error, if it's not a success result).
 *
 * result is true if successful, false if not.
 */
bool
handleCopyOut(PGconn *conn, FILE *copystream, PGresult **res)
{
	bool		OK = true;
	char	   *buf;
	int			ret;

	for (;;)
	{
		ret = PQgetCopyData(conn, &buf, 0);

		if (ret < 0)
			break;				/* done or server/connection error */

		if (buf)
		{
			if (OK && copystream && fwrite(buf, 1, ret, copystream) != ret)
			{
				pg_log_error("could not write COPY data: %m");
				/* complain only once, keep reading data from server */
				OK = false;
			}
			PQfreemem(buf);
		}
	}

	if (OK && copystream && fflush(copystream))
	{
		pg_log_error("could not write COPY data: %m");
		OK = false;
	}

	if (ret == -2)
	{
		pg_log_error("COPY data transfer failed: %s", PQerrorMessage(conn));
		OK = false;
	}

	/*
	 * Check command status and return to normal libpq state.
	 *
	 * If for some reason libpq is still reporting PGRES_COPY_OUT state, we
	 * would like to forcibly exit that state, since our caller would be
	 * unable to distinguish that situation from reaching the next COPY in a
	 * command string that happened to contain two consecutive COPY TO STDOUT
	 * commands.  However, libpq provides no API for doing that, and in
	 * principle it's a libpq bug anyway if PQgetCopyData() returns -1 or -2
	 * but hasn't exited COPY_OUT state internally.  So we ignore the
	 * possibility here.
	 */
	*res = PQgetResult(conn);
	if (PQresultStatus(*res) != PGRES_COMMAND_OK)
	{
		pg_log_info("%s", PQerrorMessage(conn));
		OK = false;
	}

	return OK;
}

/*
 * handleCopyIn
 * sends data to complete a COPY ... FROM STDIN command
 *
 * conn should be a database connection that you just issued COPY FROM on
 * and got back a PGRES_COPY_IN result.
 * copystream is the file stream to read the data from.
 * isbinary can be set from PQbinaryTuples().
 * The final status for the COPY is returned into *res (but note
 * we already reported the error, if it's not a success result).
 *
 * result is true if successful, false if not.
 */

/* read chunk size for COPY IN - size is not critical */
#define COPYBUFSIZ 8192

bool
handleCopyIn(PGconn *conn, FILE *copystream, bool isbinary, PGresult **res)
{
	bool		OK;
	char		buf[COPYBUFSIZ];
	bool		showprompt;

	/*
	 * Establish longjmp destination for exiting from wait-for-input. (This is
	 * only effective while sigint_interrupt_enabled is TRUE.)
	 */
	if (sigsetjmp(sigint_interrupt_jmp, 1) != 0)
	{
		/* got here with longjmp */

		/* Terminate data transfer */
		PQputCopyEnd(conn,
					 (PQprotocolVersion(conn) < 3) ? NULL :
					 _("canceled by user"));

		OK = false;
		goto copyin_cleanup;
	}

	/* Prompt if interactive input */
	if (isatty(fileno(copystream)))
	{
		showprompt = true;
		if (!pset.quiet)
			puts(_("Enter data to be copied followed by a newline.\n"
				   "End with a backslash and a period on a line by itself, or an EOF signal."));
	}
	else
		showprompt = false;

	OK = true;

	if (isbinary)
	{
		/* interactive input probably silly, but give one prompt anyway */
		if (showprompt)
		{
			const char *prompt = get_prompt(PROMPT_COPY, NULL);

			fputs(prompt, stdout);
			fflush(stdout);
		}

		for (;;)
		{
			int			buflen;

			/* enable longjmp while waiting for input */
			sigint_interrupt_enabled = true;

			buflen = fread(buf, 1, COPYBUFSIZ, copystream);

			sigint_interrupt_enabled = false;

			if (buflen <= 0)
				break;

			if (PQputCopyData(conn, buf, buflen) <= 0)
			{
				OK = false;
				break;
			}
		}
	}
	else
	{
		bool		copydone = false;
		int			buflen;
		bool		at_line_begin = true;

		/*
		 * In text mode, we have to read the input one line at a time, so that
		 * we can stop reading at the EOF marker (\.).  We mustn't read beyond
		 * the EOF marker, because if the data was inlined in a SQL script, we
		 * would eat up the commands after the EOF marker.
		 */
		buflen = 0;
		while (!copydone)
		{
			char	   *fgresult;

			if (at_line_begin && showprompt)
			{
				const char *prompt = get_prompt(PROMPT_COPY, NULL);

				fputs(prompt, stdout);
				fflush(stdout);
			}

			/* enable longjmp while waiting for input */
			sigint_interrupt_enabled = true;

			fgresult = fgets(&buf[buflen], COPYBUFSIZ - buflen, copystream);

			sigint_interrupt_enabled = false;

			if (!fgresult)
				copydone = true;
			else
			{
				int			linelen;

				linelen = strlen(fgresult);
				buflen += linelen;

				/* current line is done? */
				if (buf[buflen - 1] == '\n')
				{
					/* check for EOF marker, but not on a partial line */
					if (at_line_begin)
					{
						/*
						 * This code erroneously assumes '\.' on a line alone
						 * inside a quoted CSV string terminates the \copy.
						 * https://www.postgresql.org/message-id/E1TdNVQ-0001ju-GO@wrigleys.postgresql.org
						 *
						 * https://www.postgresql.org/message-id/bfcd57e4-8f23-4c3e-a5db-2571d09208e2@beta.fastmail.com
						 */
						if ((linelen == 3 && memcmp(fgresult, "\\.\n", 3) == 0) ||
							(linelen == 4 && memcmp(fgresult, "\\.\r\n", 4) == 0))
						{
							copydone = true;
						}
					}

					if (copystream == pset.cur_cmd_source)
					{
						pset.lineno++;
						pset.stmt_lineno++;
					}
					at_line_begin = true;
				}
				else
					at_line_begin = false;
			}

			/*
			 * If the buffer is full, or we've reached the EOF, flush it.
			 *
			 * Make sure there's always space for four more bytes in the
			 * buffer, plus a NUL terminator.  That way, an EOF marker is
			 * never split across two fgets() calls, which simplifies the
			 * logic.
			 */
			if (buflen >= COPYBUFSIZ - 5 || (copydone && buflen > 0))
			{
				if (PQputCopyData(conn, buf, buflen) <= 0)
				{
					OK = false;
					break;
				}

				buflen = 0;
			}
		}
	}

	/* Check for read error */
	if (ferror(copystream))
		OK = false;

	/*
	 * Terminate data transfer.  We can't send an error message if we're using
	 * protocol version 2.  (libpq no longer supports protocol version 2, but
	 * keep the version checks just in case you're using a pre-v14 libpq.so at
	 * runtime)
	 */
	if (PQputCopyEnd(conn,
					 (OK || PQprotocolVersion(conn) < 3) ? NULL :
					 _("aborted because of read failure")) <= 0)
		OK = false;

copyin_cleanup:

	/*
	 * Clear the EOF flag on the stream, in case copying ended due to an EOF
	 * signal.  This allows an interactive TTY session to perform another COPY
	 * FROM STDIN later.  (In non-STDIN cases, we're about to close the file
	 * anyway, so it doesn't matter.)  Although we don't ever test the flag
	 * with feof(), some fread() implementations won't read more data if it's
	 * set.  This also clears the error flag, but we already checked that.
	 */
	clearerr(copystream);

	/*
	 * Check command status and return to normal libpq state.
	 *
	 * We do not want to return with the status still PGRES_COPY_IN: our
	 * caller would be unable to distinguish that situation from reaching the
	 * next COPY in a command string that happened to contain two consecutive
	 * COPY FROM STDIN commands.  We keep trying PQputCopyEnd() in the hope
	 * it'll work eventually.  (What's actually likely to happen is that in
	 * attempting to flush the data, libpq will eventually realize that the
	 * connection is lost.  But that's fine; it will get us out of COPY_IN
	 * state, which is what we need.)
	 */
	while (*res = PQgetResult(conn), PQresultStatus(*res) == PGRES_COPY_IN)
	{
		OK = false;
		PQclear(*res);
		/* We can't send an error message if we're using protocol version 2 */
		PQputCopyEnd(conn,
					 (PQprotocolVersion(conn) < 3) ? NULL :
					 _("trying to exit copy mode"));
	}
	if (PQresultStatus(*res) != PGRES_COMMAND_OK)
	{
		pg_log_info("%s", PQerrorMessage(conn));
		OK = false;
	}

	return OK;
}