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SQLite training in Houston TX on 2019-11-05 (details)
Part of the 2019 Tcl Conference

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Overview
Comment:Add the remember(V,PTR) extension function which copies an SQL value into an application variable.
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SHA1: d2d30914d81022d7d4e1670caf9326524520deaf
User & Date: drh 2016-11-30 16:54:52
Context
2016-12-01
19:38
Avoid clearing the EP_FromJoin flag from terms in ON clauses when flattening sub-selects. Possible fix for [2df0107b]. Closed-Leaf check-in: 8bed4cd5 user: dan tags: left-join-fix
18:57
Performance improvement for GLOB and LIKE matching for patterns with two or more multi-character wildcards ("*" or "%"). check-in: 2df0ebf9 user: drh tags: trunk
17:34
Modify the patternCompare() function (used for GLOB, LIKE) to better handle patterns containing multiple wildcard characters ("*", "%"). check-in: c5e5614d user: dan tags: pattern-compare-optimization
2016-11-30
16:54
Add the remember(V,PTR) extension function which copies an SQL value into an application variable. check-in: d2d30914 user: drh tags: trunk
14:47
Fix then handling of the (oversized) integer literal -0x8000000000000000. check-in: 3816bb41 user: drh tags: trunk
2016-08-09
21:08
Prototype for the remember(V,PTR) extension function. Closed-Leaf check-in: f0942c36 user: drh tags: rememberFunc
Changes
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Changes to Makefile.in.

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  $(TOP)/ext/fts5/fts5_tcl.c \
  $(TOP)/ext/fts5/fts5_test_mi.c \
  $(TOP)/ext/fts5/fts5_test_tok.c \
  $(TOP)/ext/misc/ieee754.c \
  $(TOP)/ext/misc/nextchar.c \
  $(TOP)/ext/misc/percentile.c \
  $(TOP)/ext/misc/regexp.c \

  $(TOP)/ext/misc/series.c \
  $(TOP)/ext/misc/spellfix.c \
  $(TOP)/ext/misc/totype.c \
  $(TOP)/ext/misc/wholenumber.c

# Source code to the library files needed by the test fixture
#







>







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  $(TOP)/ext/fts5/fts5_tcl.c \
  $(TOP)/ext/fts5/fts5_test_mi.c \
  $(TOP)/ext/fts5/fts5_test_tok.c \
  $(TOP)/ext/misc/ieee754.c \
  $(TOP)/ext/misc/nextchar.c \
  $(TOP)/ext/misc/percentile.c \
  $(TOP)/ext/misc/regexp.c \
  $(TOP)/ext/misc/remember.c \
  $(TOP)/ext/misc/series.c \
  $(TOP)/ext/misc/spellfix.c \
  $(TOP)/ext/misc/totype.c \
  $(TOP)/ext/misc/wholenumber.c

# Source code to the library files needed by the test fixture
#

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  $(TOP)\ext\fts5\fts5_tcl.c \
  $(TOP)\ext\fts5\fts5_test_mi.c \
  $(TOP)\ext\fts5\fts5_test_tok.c \
  $(TOP)\ext\misc\ieee754.c \
  $(TOP)\ext\misc\nextchar.c \
  $(TOP)\ext\misc\percentile.c \
  $(TOP)\ext\misc\regexp.c \

  $(TOP)\ext\misc\series.c \
  $(TOP)\ext\misc\spellfix.c \
  $(TOP)\ext\misc\totype.c \
  $(TOP)\ext\misc\wholenumber.c

# Source code to the library files needed by the test fixture
# (non-amalgamation)







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  $(TOP)\ext\fts5\fts5_tcl.c \
  $(TOP)\ext\fts5\fts5_test_mi.c \
  $(TOP)\ext\fts5\fts5_test_tok.c \
  $(TOP)\ext\misc\ieee754.c \
  $(TOP)\ext\misc\nextchar.c \
  $(TOP)\ext\misc\percentile.c \
  $(TOP)\ext\misc\regexp.c \
  $(TOP)\ext\misc\remember.c \
  $(TOP)\ext\misc\series.c \
  $(TOP)\ext\misc\spellfix.c \
  $(TOP)\ext\misc\totype.c \
  $(TOP)\ext\misc\wholenumber.c

# Source code to the library files needed by the test fixture
# (non-amalgamation)

Added ext/misc/remember.c.









































































































































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/*
** 2016-08-09
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
**
** This file demonstrates how to create an SQL function that is a pass-through
** for integer values (it returns a copy of its argument) but also saves the
** value that is passed through into a C-language variable.  The address of
** the C-language variable is supplied as the second argument.
**
** This allows, for example, a counter to incremented and the original
** value retrieved, atomically, using a single statement:
**
**    UPDATE counterTab SET cnt=remember(cnt,$PTR)+1 WHERE id=$ID
**
** Prepare the above statement once.  Then to use it, bind the address
** of the output variable to $PTR and the id of the counter to $ID and
** run the prepared statement.
**
** One can imagine doing similar things with floating-point values and
** strings, but this demonstration extension will stick to using just
** integers.
*/
#include "sqlite3ext.h"
SQLITE_EXTENSION_INIT1
#include <assert.h>

/*
**      remember(V,PTR)
**
** Return the integer value V.  Also save the value of V in a
** C-language variable whose address is PTR.
*/
static void rememberFunc(
  sqlite3_context *pCtx,
  int argc,
  sqlite3_value **argv
){
  sqlite3_int64 v;
  sqlite3_int64 ptr;
  assert( argc==2 );
  v = sqlite3_value_int64(argv[0]);
  ptr = sqlite3_value_int64(argv[1]);
  *((sqlite3_int64*)ptr) = v;
  sqlite3_result_int64(pCtx, v);
}

#ifdef _WIN32
__declspec(dllexport)
#endif
int sqlite3_remember_init(
  sqlite3 *db, 
  char **pzErrMsg, 
  const sqlite3_api_routines *pApi
){
  int rc = SQLITE_OK;
  SQLITE_EXTENSION_INIT2(pApi);
  rc = sqlite3_create_function(db, "remember", 2, SQLITE_UTF8, 0,
                               rememberFunc, 0, 0);
  return rc;
}

Changes to main.mk.

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  $(TOP)/ext/misc/eval.c \
  $(TOP)/ext/misc/fileio.c \
  $(TOP)/ext/misc/fuzzer.c \
  $(TOP)/ext/misc/ieee754.c \
  $(TOP)/ext/misc/nextchar.c \
  $(TOP)/ext/misc/percentile.c \
  $(TOP)/ext/misc/regexp.c \

  $(TOP)/ext/misc/series.c \
  $(TOP)/ext/misc/spellfix.c \
  $(TOP)/ext/misc/totype.c \
  $(TOP)/ext/misc/wholenumber.c \
  $(TOP)/ext/misc/vfslog.c \
  $(TOP)/ext/fts5/fts5_tcl.c \
  $(TOP)/ext/fts5/fts5_test_mi.c \







>







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  $(TOP)/ext/misc/eval.c \
  $(TOP)/ext/misc/fileio.c \
  $(TOP)/ext/misc/fuzzer.c \
  $(TOP)/ext/misc/ieee754.c \
  $(TOP)/ext/misc/nextchar.c \
  $(TOP)/ext/misc/percentile.c \
  $(TOP)/ext/misc/regexp.c \
  $(TOP)/ext/misc/remember.c \
  $(TOP)/ext/misc/series.c \
  $(TOP)/ext/misc/spellfix.c \
  $(TOP)/ext/misc/totype.c \
  $(TOP)/ext/misc/wholenumber.c \
  $(TOP)/ext/misc/vfslog.c \
  $(TOP)/ext/fts5/fts5_tcl.c \
  $(TOP)/ext/fts5/fts5_test_mi.c \

Changes to src/test1.c.

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  extern int sqlite3_eval_init(sqlite3*,char**,const sqlite3_api_routines*);
  extern int sqlite3_fileio_init(sqlite3*,char**,const sqlite3_api_routines*);
  extern int sqlite3_fuzzer_init(sqlite3*,char**,const sqlite3_api_routines*);
  extern int sqlite3_ieee_init(sqlite3*,char**,const sqlite3_api_routines*);
  extern int sqlite3_nextchar_init(sqlite3*,char**,const sqlite3_api_routines*);
  extern int sqlite3_percentile_init(sqlite3*,char**,const sqlite3_api_routines*);
  extern int sqlite3_regexp_init(sqlite3*,char**,const sqlite3_api_routines*);

  extern int sqlite3_series_init(sqlite3*,char**,const sqlite3_api_routines*);
  extern int sqlite3_spellfix_init(sqlite3*,char**,const sqlite3_api_routines*);
  extern int sqlite3_totype_init(sqlite3*,char**,const sqlite3_api_routines*);
  extern int sqlite3_wholenumber_init(sqlite3*,char**,const sqlite3_api_routines*);
  static const struct {
    const char *zExtName;
    int (*pInit)(sqlite3*,char**,const sqlite3_api_routines*);
................................................................................
    { "eval",                  sqlite3_eval_init                 },
    { "fileio",                sqlite3_fileio_init               },
    { "fuzzer",                sqlite3_fuzzer_init               },
    { "ieee754",               sqlite3_ieee_init                 },
    { "nextchar",              sqlite3_nextchar_init             },
    { "percentile",            sqlite3_percentile_init           },
    { "regexp",                sqlite3_regexp_init               },

    { "series",                sqlite3_series_init               },
    { "spellfix",              sqlite3_spellfix_init             },
    { "totype",                sqlite3_totype_init               },
    { "wholenumber",           sqlite3_wholenumber_init          },
  };
  sqlite3 *db;
  const char *zName;







>







 







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  extern int sqlite3_eval_init(sqlite3*,char**,const sqlite3_api_routines*);
  extern int sqlite3_fileio_init(sqlite3*,char**,const sqlite3_api_routines*);
  extern int sqlite3_fuzzer_init(sqlite3*,char**,const sqlite3_api_routines*);
  extern int sqlite3_ieee_init(sqlite3*,char**,const sqlite3_api_routines*);
  extern int sqlite3_nextchar_init(sqlite3*,char**,const sqlite3_api_routines*);
  extern int sqlite3_percentile_init(sqlite3*,char**,const sqlite3_api_routines*);
  extern int sqlite3_regexp_init(sqlite3*,char**,const sqlite3_api_routines*);
  extern int sqlite3_remember_init(sqlite3*,char**,const sqlite3_api_routines*);
  extern int sqlite3_series_init(sqlite3*,char**,const sqlite3_api_routines*);
  extern int sqlite3_spellfix_init(sqlite3*,char**,const sqlite3_api_routines*);
  extern int sqlite3_totype_init(sqlite3*,char**,const sqlite3_api_routines*);
  extern int sqlite3_wholenumber_init(sqlite3*,char**,const sqlite3_api_routines*);
  static const struct {
    const char *zExtName;
    int (*pInit)(sqlite3*,char**,const sqlite3_api_routines*);
................................................................................
    { "eval",                  sqlite3_eval_init                 },
    { "fileio",                sqlite3_fileio_init               },
    { "fuzzer",                sqlite3_fuzzer_init               },
    { "ieee754",               sqlite3_ieee_init                 },
    { "nextchar",              sqlite3_nextchar_init             },
    { "percentile",            sqlite3_percentile_init           },
    { "regexp",                sqlite3_regexp_init               },
    { "remember",              sqlite3_remember_init             },
    { "series",                sqlite3_series_init               },
    { "spellfix",              sqlite3_spellfix_init             },
    { "totype",                sqlite3_totype_init               },
    { "wholenumber",           sqlite3_wholenumber_init          },
  };
  sqlite3 *db;
  const char *zName;

Changes to test/tabfunc01.test.

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ifcapable !vtab {
  finish_test
  return
}
load_static_extension db series
load_static_extension db carray


do_execsql_test tabfunc01-1.1 {
  SELECT *, '|' FROM generate_series WHERE start=1 AND stop=9 AND step=2;
} {1 | 3 | 5 | 7 | 9 |}
do_execsql_test tabfunc01-1.2 {
  SELECT *, '|' FROM generate_series LIMIT 5;
} {0 | 1 | 2 | 3 | 4 |}
................................................................................

do_test tabfunc01-720 {
  set PTR [int64array_addr 5 7 13 17 23]
  db eval {
    SELECT b FROM t600, carray($PTR,5,'int64') WHERE a=value;
  }
} {(005) (007) (013) (017) (023)}














do_test tabfunc01-730 {
  set PTR [doublearray_addr 5.0 7.0 13.0 17.0 23.0]
  db eval {
    SELECT b FROM t600, carray($PTR,5,'double') WHERE a=value;
  }
} {(005) (007) (013) (017) (023)}







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ifcapable !vtab {
  finish_test
  return
}
load_static_extension db series
load_static_extension db carray
load_static_extension db remember

do_execsql_test tabfunc01-1.1 {
  SELECT *, '|' FROM generate_series WHERE start=1 AND stop=9 AND step=2;
} {1 | 3 | 5 | 7 | 9 |}
do_execsql_test tabfunc01-1.2 {
  SELECT *, '|' FROM generate_series LIMIT 5;
} {0 | 1 | 2 | 3 | 4 |}
................................................................................

do_test tabfunc01-720 {
  set PTR [int64array_addr 5 7 13 17 23]
  db eval {
    SELECT b FROM t600, carray($PTR,5,'int64') WHERE a=value;
  }
} {(005) (007) (013) (017) (023)}
do_test tabfunc01-721 {
  db eval {
    SELECT remember(123,$PTR);
    SELECT value FROM carray($PTR,5,'int64');
  }
} {123 123 7 13 17 23}
do_test tabfunc01-722 {
  set PTR2 [expr {$PTR+16}]
  db eval {
    SELECT remember(987,$PTR2);
    SELECT value FROM carray($PTR,5,'int64');
  }
} {987 123 7 987 17 23}

do_test tabfunc01-730 {
  set PTR [doublearray_addr 5.0 7.0 13.0 17.0 23.0]
  db eval {
    SELECT b FROM t600, carray($PTR,5,'double') WHERE a=value;
  }
} {(005) (007) (013) (017) (023)}