2018-03-22 15:42:03 +01:00
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/*-------------------------------------------------------------------------
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* A stack of automaton states to handle nested conditionals.
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*
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* This file describes a stack of automaton states which
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* allow a manage nested conditionals.
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*
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* It is used by:
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2019-06-03 06:44:03 +02:00
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* - "psql" interpreter for handling \if ... \endif
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* - "pgbench" interpreter for handling \if ... \endif
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2018-03-22 15:42:03 +01:00
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* - "pgbench" syntax checker to test for proper nesting
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*
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* The stack holds the state of enclosing conditionals (are we in
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* a true branch? in a false branch? have we already encountered
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* a true branch?) so that the interpreter knows whether to execute
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* code and whether to evaluate conditions.
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Support \if ... \elif ... \else ... \endif in psql scripting.
This patch adds nestable conditional blocks to psql. The control
structure feature per se is complete, but the boolean expressions
understood by \if and \elif are pretty primitive; basically, after
variable substitution and backtick expansion, the result has to be
"true" or "false" or one of the other standard spellings of a boolean
value. But that's enough for many purposes, since you can always
do the heavy lifting on the server side; and we can extend it later.
Along the way, pay down some of the technical debt that had built up
around psql/command.c:
* Refactor exec_command() into a function per command, instead of
being a 1500-line monstrosity. This makes the file noticeably longer
because of repetitive function header/trailer overhead, but it seems
much more readable.
* Teach psql_get_variable() and psqlscanslash.l to suppress variable
substitution and backtick expansion on the basis of the conditional
stack state, thereby allowing removal of the OT_NO_EVAL kluge.
* Fix the no-doubt-once-expedient hack of sometimes silently substituting
mainloop.c's previous_buf for query_buf when calling HandleSlashCmds.
(It's a bit remarkable that commands like \r worked at all with that.)
Recall of a previous query is now done explicitly in the slash commands
where that should happen.
Corey Huinker, reviewed by Fabien Coelho, further hacking by me
Discussion: https://postgr.es/m/CADkLM=c94OSRTnat=LX0ivNq4pxDNeoomFfYvBKM5N_xfmLtAA@mail.gmail.com
2017-03-30 18:59:11 +02:00
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*
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2021-01-02 19:06:25 +01:00
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* Copyright (c) 2000-2021, PostgreSQL Global Development Group
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Support \if ... \elif ... \else ... \endif in psql scripting.
This patch adds nestable conditional blocks to psql. The control
structure feature per se is complete, but the boolean expressions
understood by \if and \elif are pretty primitive; basically, after
variable substitution and backtick expansion, the result has to be
"true" or "false" or one of the other standard spellings of a boolean
value. But that's enough for many purposes, since you can always
do the heavy lifting on the server side; and we can extend it later.
Along the way, pay down some of the technical debt that had built up
around psql/command.c:
* Refactor exec_command() into a function per command, instead of
being a 1500-line monstrosity. This makes the file noticeably longer
because of repetitive function header/trailer overhead, but it seems
much more readable.
* Teach psql_get_variable() and psqlscanslash.l to suppress variable
substitution and backtick expansion on the basis of the conditional
stack state, thereby allowing removal of the OT_NO_EVAL kluge.
* Fix the no-doubt-once-expedient hack of sometimes silently substituting
mainloop.c's previous_buf for query_buf when calling HandleSlashCmds.
(It's a bit remarkable that commands like \r worked at all with that.)
Recall of a previous query is now done explicitly in the slash commands
where that should happen.
Corey Huinker, reviewed by Fabien Coelho, further hacking by me
Discussion: https://postgr.es/m/CADkLM=c94OSRTnat=LX0ivNq4pxDNeoomFfYvBKM5N_xfmLtAA@mail.gmail.com
2017-03-30 18:59:11 +02:00
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*
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2018-03-22 15:42:03 +01:00
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* src/include/fe_utils/conditional.h
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*
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*-------------------------------------------------------------------------
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Support \if ... \elif ... \else ... \endif in psql scripting.
This patch adds nestable conditional blocks to psql. The control
structure feature per se is complete, but the boolean expressions
understood by \if and \elif are pretty primitive; basically, after
variable substitution and backtick expansion, the result has to be
"true" or "false" or one of the other standard spellings of a boolean
value. But that's enough for many purposes, since you can always
do the heavy lifting on the server side; and we can extend it later.
Along the way, pay down some of the technical debt that had built up
around psql/command.c:
* Refactor exec_command() into a function per command, instead of
being a 1500-line monstrosity. This makes the file noticeably longer
because of repetitive function header/trailer overhead, but it seems
much more readable.
* Teach psql_get_variable() and psqlscanslash.l to suppress variable
substitution and backtick expansion on the basis of the conditional
stack state, thereby allowing removal of the OT_NO_EVAL kluge.
* Fix the no-doubt-once-expedient hack of sometimes silently substituting
mainloop.c's previous_buf for query_buf when calling HandleSlashCmds.
(It's a bit remarkable that commands like \r worked at all with that.)
Recall of a previous query is now done explicitly in the slash commands
where that should happen.
Corey Huinker, reviewed by Fabien Coelho, further hacking by me
Discussion: https://postgr.es/m/CADkLM=c94OSRTnat=LX0ivNq4pxDNeoomFfYvBKM5N_xfmLtAA@mail.gmail.com
2017-03-30 18:59:11 +02:00
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*/
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#ifndef CONDITIONAL_H
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#define CONDITIONAL_H
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/*
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* Possible states of a single level of \if block.
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*/
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typedef enum ifState
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{
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IFSTATE_NONE = 0, /* not currently in an \if block */
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IFSTATE_TRUE, /* currently in an \if or \elif that is true
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* and all parent branches (if any) are true */
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IFSTATE_FALSE, /* currently in an \if or \elif that is false
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* but no true branch has yet been seen, and
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* all parent branches (if any) are true */
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IFSTATE_IGNORED, /* currently in an \elif that follows a true
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* branch, or the whole \if is a child of a
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* false parent branch */
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IFSTATE_ELSE_TRUE, /* currently in an \else that is true and all
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* parent branches (if any) are true */
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IFSTATE_ELSE_FALSE /* currently in an \else that is false or
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* ignored */
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} ifState;
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/*
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* The state of nested \ifs is stored in a stack.
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*
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* query_len is used to determine what accumulated text to throw away at the
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* end of an inactive branch. (We could, perhaps, teach the lexer to not add
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* stuff to the query buffer in the first place when inside an inactive branch;
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* but that would be very invasive.) We also need to save and restore the
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* lexer's parenthesis nesting depth when throwing away text. (We don't need
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* to save and restore any of its other state, such as comment nesting depth,
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* because a backslash command could never appear inside a comment or SQL
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* literal.)
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*/
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typedef struct IfStackElem
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{
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ifState if_state; /* current state, see enum above */
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int query_len; /* length of query_buf at last branch start */
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int paren_depth; /* parenthesis depth at last branch start */
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struct IfStackElem *next; /* next surrounding \if, if any */
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} IfStackElem;
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typedef struct ConditionalStackData
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{
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IfStackElem *head;
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} ConditionalStackData;
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typedef struct ConditionalStackData *ConditionalStack;
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extern ConditionalStack conditional_stack_create(void);
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extern void conditional_stack_destroy(ConditionalStack cstack);
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2018-03-22 15:42:03 +01:00
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extern int conditional_stack_depth(ConditionalStack cstack);
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Support \if ... \elif ... \else ... \endif in psql scripting.
This patch adds nestable conditional blocks to psql. The control
structure feature per se is complete, but the boolean expressions
understood by \if and \elif are pretty primitive; basically, after
variable substitution and backtick expansion, the result has to be
"true" or "false" or one of the other standard spellings of a boolean
value. But that's enough for many purposes, since you can always
do the heavy lifting on the server side; and we can extend it later.
Along the way, pay down some of the technical debt that had built up
around psql/command.c:
* Refactor exec_command() into a function per command, instead of
being a 1500-line monstrosity. This makes the file noticeably longer
because of repetitive function header/trailer overhead, but it seems
much more readable.
* Teach psql_get_variable() and psqlscanslash.l to suppress variable
substitution and backtick expansion on the basis of the conditional
stack state, thereby allowing removal of the OT_NO_EVAL kluge.
* Fix the no-doubt-once-expedient hack of sometimes silently substituting
mainloop.c's previous_buf for query_buf when calling HandleSlashCmds.
(It's a bit remarkable that commands like \r worked at all with that.)
Recall of a previous query is now done explicitly in the slash commands
where that should happen.
Corey Huinker, reviewed by Fabien Coelho, further hacking by me
Discussion: https://postgr.es/m/CADkLM=c94OSRTnat=LX0ivNq4pxDNeoomFfYvBKM5N_xfmLtAA@mail.gmail.com
2017-03-30 18:59:11 +02:00
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extern void conditional_stack_push(ConditionalStack cstack, ifState new_state);
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extern bool conditional_stack_pop(ConditionalStack cstack);
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extern ifState conditional_stack_peek(ConditionalStack cstack);
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extern bool conditional_stack_poke(ConditionalStack cstack, ifState new_state);
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extern bool conditional_stack_empty(ConditionalStack cstack);
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extern bool conditional_active(ConditionalStack cstack);
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extern void conditional_stack_set_query_len(ConditionalStack cstack, int len);
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extern int conditional_stack_get_query_len(ConditionalStack cstack);
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extern void conditional_stack_set_paren_depth(ConditionalStack cstack, int depth);
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extern int conditional_stack_get_paren_depth(ConditionalStack cstack);
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#endif /* CONDITIONAL_H */
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