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

1 files changed, 2 insertions, 20 deletions

diff --git a/src/bin/psql/psqlscan.h b/src/bin/psql/psqlscan.h
index 82c66dcdf9c..d515ce34f23 100644
--- a/src/bin/psql/psqlscan.h
+++ b/src/bin/psql/psqlscan.h
@@ -25,17 +25,6 @@ typedef enum
 	PSCAN_EOL					/* end of line, SQL possibly complete */
 } PsqlScanResult;
 
-/* Different ways for scan_slash_option to handle parameter words */
-enum slash_option_type
-{
-	OT_NORMAL,					/* normal case */
-	OT_SQLID,					/* treat as SQL identifier */
-	OT_SQLIDHACK,				/* SQL identifier, but don't downcase */
-	OT_FILEPIPE,				/* it's a filename or pipe */
-	OT_WHOLE_LINE,				/* just snarf the rest of the line */
-	OT_NO_EVAL					/* no expansion of backticks or variables */
-};
-
 /* Callback functions to be used by the lexer */
 typedef struct PsqlScanCallbacks
 {
@@ -61,15 +50,8 @@ extern PsqlScanResult psql_scan(PsqlScanState state,
 
 extern void psql_scan_reset(PsqlScanState state);
 
-extern bool psql_scan_in_quote(PsqlScanState state);
-
-extern char *psql_scan_slash_command(PsqlScanState state);
-
-extern char *psql_scan_slash_option(PsqlScanState state,
-					   enum slash_option_type type,
-					   char *quote,
-					   bool semicolon);
+extern void psql_scan_reselect_sql_lexer(PsqlScanState state);
 
-extern void psql_scan_slash_command_end(PsqlScanState state);
+extern bool psql_scan_in_quote(PsqlScanState state);
 
 #endif   /* PSQLSCAN_H */