Clean up temporary-memory management during ispell dictionary loading.

Add explicit initialization and cleanup functions to spell.c, and keep
all working state in the already-existing ISpellDict struct.  This lets us
get rid of a static variable along with some extremely shaky assumptions
about usage of child memory contexts.

This commit is just code beautification and has no impact on functionality
or performance, but it opens the way to a less-grotty implementation of
Pavel's memory-saving hack, which will follow shortly.

src/backend/tsearch/dict_ispell.c

@@ -19,7 +19,6 @@
 #include "tsearch/ts_public.h"
 #include "tsearch/ts_utils.h"
 #include "utils/builtins.h"
-#include "utils/memutils.h"
 
 
 typedef struct
@@ -40,6 +39,8 @@ dispell_init(PG_FUNCTION_ARGS)
 
 	d = (DictISpell *) palloc0(sizeof(DictISpell));
 
+	NIStartBuild(&(d->obj));
+
 	foreach(l, dictoptions)
 	{
 		DefElem    *defel = (DefElem *) lfirst(l);
@@ -102,7 +103,7 @@ dispell_init(PG_FUNCTION_ARGS)
 				 errmsg("missing DictFile parameter")));
 	}
 
-	MemoryContextDeleteChildren(CurrentMemoryContext);
+	NIFinishBuild(&(d->obj));
 
 	PG_RETURN_POINTER(d);
 }

src/backend/tsearch/spell.c

@@ -21,42 +21,57 @@
 
 /*
  * Initialization requires a lot of memory that's not needed
- * after the initialization is done.  In init function,
- * CurrentMemoryContext is a long lived memory context associated
- * with the dictionary cache entry, so we use a temporary context
- * for the short-lived stuff.
+ * after the initialization is done.  During initialization,
+ * CurrentMemoryContext is the long-lived memory context associated
+ * with the dictionary cache entry.  We keep the short-lived stuff
+ * in the Conf->buildCxt context.
  */
-static MemoryContext tmpCtx = NULL;
+#define tmpalloc(sz)  MemoryContextAlloc(Conf->buildCxt, (sz))
+#define tmpalloc0(sz)  MemoryContextAllocZero(Conf->buildCxt, (sz))
 
-#define tmpalloc(sz)  MemoryContextAlloc(tmpCtx, (sz))
-#define tmpalloc0(sz)  MemoryContextAllocZero(tmpCtx, (sz))
-
-static void
-checkTmpCtx(void)
+/*
+ * Prepare for constructing an ISpell dictionary.
+ *
+ * The IspellDict struct is assumed to be zeroed when allocated.
+ */
+void
+NIStartBuild(IspellDict *Conf)
 {
 	/*
-	 * XXX: This assumes that CurrentMemoryContext doesn't have any children
-	 * other than the one we create here.
+	 * The temp context is a child of CurTransactionContext, so that it will
+	 * go away automatically on error.
 	 */
-	if (CurrentMemoryContext->firstchild == NULL)
-	{
-		tmpCtx = AllocSetContextCreate(CurrentMemoryContext,
-									   "Ispell dictionary init context",
-									   ALLOCSET_DEFAULT_MINSIZE,
-									   ALLOCSET_DEFAULT_INITSIZE,
-									   ALLOCSET_DEFAULT_MAXSIZE);
-	}
-	else
-		tmpCtx = CurrentMemoryContext->firstchild;
+	Conf->buildCxt = AllocSetContextCreate(CurTransactionContext,
+										   "Ispell dictionary init context",
+										   ALLOCSET_DEFAULT_MINSIZE,
+										   ALLOCSET_DEFAULT_INITSIZE,
+										   ALLOCSET_DEFAULT_MAXSIZE);
 }
 
+/*
+ * Clean up when dictionary construction is complete.
+ */
+void
+NIFinishBuild(IspellDict *Conf)
+{
+	/* Release no-longer-needed temp memory */
+	MemoryContextDelete(Conf->buildCxt);
+	/* Just for cleanliness, zero the now-dangling pointers */
+	Conf->buildCxt = NULL;
+	Conf->Spell = NULL;
+}
+
+
+/*
+ * Apply lowerstr(), producing a temporary result (in the buildCxt).
+ */
 static char *
-lowerstr_ctx(char *src)
+lowerstr_ctx(IspellDict *Conf, const char *src)
 {
 	MemoryContext saveCtx;
 	char	   *dst;
 
-	saveCtx = MemoryContextSwitchTo(tmpCtx);
+	saveCtx = MemoryContextSwitchTo(Conf->buildCxt);
 	dst = lowerstr(src);
 	MemoryContextSwitchTo(saveCtx);
 
@@ -120,6 +135,7 @@ strbcmp(const unsigned char *s1, const unsigned char *s2)
 
 	return 0;
 }
+
 static int
 strbncmp(const unsigned char *s1, const unsigned char *s2, size_t count)
 {
@@ -196,8 +212,6 @@ NIImportDictionary(IspellDict *Conf, const char *filename)
 	tsearch_readline_state trst;
 	char	   *line;
 
-	checkTmpCtx();
-
 	if (!tsearch_readline_begin(&trst, filename))
 		ereport(ERROR,
 				(errcode(ERRCODE_CONFIG_FILE_ERROR),
@@ -242,7 +256,7 @@ NIImportDictionary(IspellDict *Conf, const char *filename)
 			}
 			s += pg_mblen(s);
 		}
-		pstr = lowerstr_ctx(line);
+		pstr = lowerstr_ctx(Conf, line);
 
 		NIAddSpell(Conf, pstr, flag);
 		pfree(pstr);
@@ -545,8 +559,6 @@ NIImportOOAffixes(IspellDict *Conf, const char *filename)
 	char		scanbuf[BUFSIZ];
 	char	   *recoded;
 
-	checkTmpCtx();
-
 	/* read file to find any flag */
 	memset(Conf->flagval, 0, sizeof(Conf->flagval));
 	Conf->usecompound = false;
@@ -624,7 +636,7 @@ NIImportOOAffixes(IspellDict *Conf, const char *filename)
 
 		if (ptype)
 			pfree(ptype);
-		ptype = lowerstr_ctx(type);
+		ptype = lowerstr_ctx(Conf, type);
 		if (scanread < 4 || (STRNCMP(ptype, "sfx") && STRNCMP(ptype, "pfx")))
 			goto nextline;
 
@@ -646,7 +658,7 @@ NIImportOOAffixes(IspellDict *Conf, const char *filename)
 
 			if (strlen(sflag) != 1 || flag != *sflag || flag == 0)
 				goto nextline;
-			prepl = lowerstr_ctx(repl);
+			prepl = lowerstr_ctx(Conf, repl);
 			/* affix flag */
 			if ((ptr = strchr(prepl, '/')) != NULL)
 			{
@@ -658,8 +670,8 @@ NIImportOOAffixes(IspellDict *Conf, const char *filename)
 					ptr++;
 				}
 			}
-			pfind = lowerstr_ctx(find);
-			pmask = lowerstr_ctx(mask);
+			pfind = lowerstr_ctx(Conf, find);
+			pmask = lowerstr_ctx(Conf, mask);
 			if (t_iseq(find, '0'))
 				*pfind = '\0';
 			if (t_iseq(repl, '0'))
@@ -702,8 +714,6 @@ NIImportAffixes(IspellDict *Conf, const char *filename)
 	bool		oldformat = false;
 	char	   *recoded = NULL;
 
-	checkTmpCtx();
-
 	if (!tsearch_readline_begin(&trst, filename))
 		ereport(ERROR,
 				(errcode(ERRCODE_CONFIG_FILE_ERROR),
@@ -945,8 +955,6 @@ NISortDictionary(IspellDict *Conf)
 	int			naffix = 0;
 	int			curaffix;
 
-	checkTmpCtx();
-
 	/* compress affixes */
 
 	/* Count the number of different flags used in the dictionary */
@@ -985,8 +993,6 @@ NISortDictionary(IspellDict *Conf)
 
 	qsort((void *) Conf->Spell, Conf->nspell, sizeof(SPELL *), cmpspell);
 	Conf->Dictionary = mkSPNode(Conf, 0, Conf->nspell, 0);
-
-	Conf->Spell = NULL;
 }
 
 static AffixNode *
@@ -1123,8 +1129,6 @@ NISortAffixes(IspellDict *Conf)
 	CMPDAffix  *ptr;
 	int			firstsuffix = Conf->naffixes;
 
-	checkTmpCtx();
-
 	if (Conf->naffixes == 0)
 		return;
 

src/include/tsearch/dicts/spell.h

@@ -138,14 +138,6 @@ typedef struct
 	int			naffixes;
 	AFFIX	   *Affix;
 
-	/*
-	 * Temporary array of all words in the dict file. Only used during
-	 * initialization
-	 */
-	SPELL	  **Spell;
-	int			nspell;			/* number of valid entries in Spell array */
-	int			mspell;			/* allocated length of Spell array */
-
 	AffixNode  *Suffix;
 	AffixNode  *Prefix;
 
@@ -158,12 +150,26 @@ typedef struct
 
 	unsigned char flagval[256];
 	bool		usecompound;
+
+	/*
+	 * Remaining fields are only used during dictionary construction;
+	 * they are set up by NIStartBuild and cleared by NIFinishBuild.
+	 */
+	MemoryContext	buildCxt;	/* temp context for construction */
+
+	/* Temporary array of all words in the dict file */
+	SPELL	  **Spell;
+	int			nspell;			/* number of valid entries in Spell array */
+	int			mspell;			/* allocated length of Spell array */
 } IspellDict;
 
 extern TSLexeme *NINormalizeWord(IspellDict *Conf, char *word);
+
+extern void NIStartBuild(IspellDict *Conf);
 extern void NIImportAffixes(IspellDict *Conf, const char *filename);
 extern void NIImportDictionary(IspellDict *Conf, const char *filename);
 extern void NISortDictionary(IspellDict *Conf);
 extern void NISortAffixes(IspellDict *Conf);
+extern void NIFinishBuild(IspellDict *Conf);
 
 #endif