postgresql/src/bin/psql/psqlscan.h

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/*
* psql - the PostgreSQL interactive terminal
*
* Copyright (c) 2000-2016, PostgreSQL Global Development Group
*
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* src/bin/psql/psqlscan.h
*/
#ifndef PSQLSCAN_H
#define PSQLSCAN_H
#include "pqexpbuffer.h"
#include "prompt.h"
/* Abstract type for lexer's internal state */
typedef struct PsqlScanStateData *PsqlScanState;
/* Termination states for psql_scan() */
typedef enum
{
PSCAN_SEMICOLON, /* found command-ending semicolon */
PSCAN_BACKSLASH, /* found backslash command */
PSCAN_INCOMPLETE, /* end of line, SQL statement incomplete */
PSCAN_EOL /* end of line, SQL possibly complete */
} PsqlScanResult;
/* Callback functions to be used by the lexer */
typedef struct PsqlScanCallbacks
{
/* Fetch value of a variable, as a pfree'able string; NULL if unknown */
/* This pointer can be NULL if no variable substitution is wanted */
char *(*get_variable) (const char *varname, bool escape, bool as_ident);
/* Print an error message someplace appropriate */
/* (very old gcc versions don't support attributes on function pointers) */
#if defined(__GNUC__) && __GNUC__ < 4
void (*write_error) (const char *fmt,...);
#else
void (*write_error) (const char *fmt,...) pg_attribute_printf(1, 2);
#endif
} PsqlScanCallbacks;
extern PsqlScanState psql_scan_create(const PsqlScanCallbacks *callbacks);
extern void psql_scan_destroy(PsqlScanState state);
extern void psql_scan_setup(PsqlScanState state,
const char *line, int line_len,
int encoding, bool std_strings);
extern void psql_scan_finish(PsqlScanState state);
extern PsqlScanResult psql_scan(PsqlScanState state,
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PQExpBuffer query_buf,
promptStatus_t *prompt);
extern void psql_scan_reset(PsqlScanState state);
Split psql's lexer into two separate .l files for SQL and backslash cases. This gets us to a point where psqlscan.l can be used by other frontend programs for the same purpose psql uses it for, ie to detect when it's collected a complete SQL command from input that is divided across line boundaries. Moreover, other programs can supply their own lexers for backslash commands of their own choosing. A follow-on patch will use this in pgbench. The end result here is roughly the same as in Kyotaro Horiguchi's 0001-Make-SQL-parser-part-of-psqlscan-independent-from-ps.patch, although the details of the method for switching between lexers are quite different. Basically, in this patch we share the entire PsqlScanState, YY_BUFFER_STATE stack, *and* yyscan_t between different lexers. The only thing we need to do to switch to a different lexer is to make sure the start_state is valid for the new lexer. This works because flex doesn't keep any other persistent state that depends on the specific lexing tables generated for a particular .l file. (We are assuming that both lexers are built with the same flex version, or at least versions that are compatible with respect to the contents of yyscan_t; but that doesn't seem likely to be a big problem in practice, considering how slowly flex changes.) Aside from being more efficient than Horiguchi-san's original solution, this avoids possible corner-case changes in semantics: the original code was capable of popping the input buffer stack while still staying in backslash-related parsing states. I'm not sure that that equates to any useful user-visible behaviors, but I'm not sure it doesn't either, so I'm loath to assume that we only need to consider the topmost buffer when parsing a backslash command. I've attempted to update the MSVC build scripts for the added .l file, but will rely on the buildfarm to see if I missed anything. Kyotaro Horiguchi and Tom Lane
2016-03-19 05:24:55 +01:00
extern void psql_scan_reselect_sql_lexer(PsqlScanState state);
Split psql's lexer into two separate .l files for SQL and backslash cases. This gets us to a point where psqlscan.l can be used by other frontend programs for the same purpose psql uses it for, ie to detect when it's collected a complete SQL command from input that is divided across line boundaries. Moreover, other programs can supply their own lexers for backslash commands of their own choosing. A follow-on patch will use this in pgbench. The end result here is roughly the same as in Kyotaro Horiguchi's 0001-Make-SQL-parser-part-of-psqlscan-independent-from-ps.patch, although the details of the method for switching between lexers are quite different. Basically, in this patch we share the entire PsqlScanState, YY_BUFFER_STATE stack, *and* yyscan_t between different lexers. The only thing we need to do to switch to a different lexer is to make sure the start_state is valid for the new lexer. This works because flex doesn't keep any other persistent state that depends on the specific lexing tables generated for a particular .l file. (We are assuming that both lexers are built with the same flex version, or at least versions that are compatible with respect to the contents of yyscan_t; but that doesn't seem likely to be a big problem in practice, considering how slowly flex changes.) Aside from being more efficient than Horiguchi-san's original solution, this avoids possible corner-case changes in semantics: the original code was capable of popping the input buffer stack while still staying in backslash-related parsing states. I'm not sure that that equates to any useful user-visible behaviors, but I'm not sure it doesn't either, so I'm loath to assume that we only need to consider the topmost buffer when parsing a backslash command. I've attempted to update the MSVC build scripts for the added .l file, but will rely on the buildfarm to see if I missed anything. Kyotaro Horiguchi and Tom Lane
2016-03-19 05:24:55 +01:00
extern bool psql_scan_in_quote(PsqlScanState state);
#endif /* PSQLSCAN_H */